Gene switches make prairie voles fall in love Epigenetic changes affect neurotransmitters that lead to pair-bond formation. Zoe Cormier 02 June 2013 Adv Exp Med Biol. 1998;449:215-24. Oxytocin, vasopressin, and the neuroendocrine basis of pair bond formation. Insel TR1, Winslow JT, Wang Z, Young LJ. Author information Abstract Several lines of evidence support a role […]

Gene switches make prairie voles fall in love

Epigenetic changes affect neurotransmitters that lead to pair-bond formation.

02 June 2013

Adv Exp Med Biol. 1998;449:215-24.

Oxytocin, vasopressin, and the neuroendocrine basis of pair bond formation.


Several lines of evidence support a role for oxytocin and vasopressin in complex social behaviors, including parental care, sex behavior, and aggression. Recent studies in a monogamous mammal, the prairie vole, suggest an additional role for both peptides in the formation of pair bonds. Central administration of oxytocin facilitates and administration of an oxytocin antagonist inhibits partner preference formation in female prairie voles. Conversely, vasopressin facilitates and a V1a receptor antagonist inhibits pair bonding in males. A potential cellular basis for these effects is the species-specific pattern of expression of oxytocin and V1a receptor in reward pathways of the prairie vole brain. At a molecular level, comparative sequencing of the oxytocin and V1a receptors reveals species differences in the promoter sequences that may guide regional expression in the brain. Transgenic mice created with the 5′ flanking region of the prairie vole oxytocin receptor gene demonstrate that sequencing in this region influence the pattern of expression within the brain. The unique promoter sequences of the prairie vole OTR and V1a receptor genes and the resulting species-specific pattern of regional expression provide a potential molecular mechanism for the evolution of pair bonding behaviors and a cellular basis for monogamy.

Oxytocin (Oxt) is a hormone, neuropeptide, and medication.[3][4] As a medication, it is used to cause contraction of the uterus in order to start labor or increase the speed of labor, and to stop bleeding following delivery.[3] For this purpose, it is given either byinjection into a muscle or into a vein.[3]

The use of oxytocin as a medication can result in excessive contraction of the uterus that can cause distress in an unborn baby. Common side effects in the mother include nausea and a slow heart rate. Serious side effects include water intoxication with an excessive dose and uterus rupture. Allergic reactions may also occur.[3]

Oxytocin is normally produced in the hypothalamus.[5][6] It plays a role in social bonding, sexual reproduction in both sexes, and during and after childbirth.[7] Oxytocin is released into the bloodstream as a hormone in response to stretching of the cervix anduterus during labor and with stimulation of the nipples from breastfeeding.[6] This helps with birth, bonding with the baby, and milk production.[6][8]

Oxytocin was discovered in 1952.[9] It is on the World Health Organization’s List of Essential Medicines, the most important medications needed in a basic health system.[10] As of 2014, the wholesale cost of the medication is US$0.1–0.56 per dose.[11]

Oxytocin has peripheral (hormonal) actions, and also has actions in the brain. Its actions are mediated by specific, oxytocin receptors. The oxytocin receptor is a G-protein-coupled receptor that requires magnesium and cholesterol. It belongs to therhodopsin-type (class I) group of G-protein-coupled receptors.

Studies have looked at oxytocin’s role in various behaviors, including orgasm, social recognition, pair bonding, anxiety, and maternal behaviors.[12]

The peripheral actions of oxytocin mainly reflect secretion from the pituitary gland. The behavioral effects of oxytocin are thought to reflect release from centrally projecting oxytocin neurons, different from those that project to the pituitary gland, or that are collaterals from them.[13] Oxytocin receptors are expressed by neurons in many parts of the brain and spinal cord, including the amygdala,ventromedial hypothalamus, septum, nucleus accumbens, and brainstem.

  • Letdown reflex: In lactating (breastfeeding) mothers, oxytocin acts at the mammary glands, causing milk to be ‘let down’ intosubareolar sinuses, from where it can be excreted via the nipple.[14] Suckling by the infant at the nipple is relayed by spinal nerves to the hypothalamus. The stimulation causes neurons that make oxytocin to fire action potentials in intermittent bursts; these bursts result in the secretion of pulses of oxytocin from the neurosecretory nerve terminals of the pituitary gland.
  • Uterine contraction: Important for cervical dilation before birth, oxytocin causes contractions during the second and third stages oflabor. Oxytocin release during breastfeeding causes mild but often painful contractions during the first few weeks of lactation. This also serves to assist the uterus in clotting the placental attachment point postpartum. However, in knockout mice lacking the oxytocin receptor, reproductive behavior and parturition are normal.[15]
  • Social behavior[16][17] and wound healing: Oxytocin is also thought to modulate inflammation by decreasing certain cytokines. Thus, the increased release in oxytocin following positive social interactions has the potential to improve wound healing. A study by Marazziti and colleagues used heterosexual couples to investigate this possibility. They found increases in plasma oxytocin following a social interaction were correlated with faster wound healing. They hypothesized this was due to oxytocin reducing inflammation, thus allowing the wound to heal more quickly. This study provides preliminary evidence that positive social interactions may directly influence aspects of health.[18] According to a study published in 2014, silencing of oxytocin receptor interneurons in the medial prefrontal cortex (mPFC) of female mice resulted in loss of social interest in male mice during the sexually receptive phase of the estrous cycle.[19]
Oxytocin evokes feelings of contentment, reductions in anxiety, and feelings of calmness and security when in the company of the mate.[20] This suggests oxytocin may be important for the inhibition of the brain regions associated with behavioral control, fear, and anxiety, thus allowing orgasm to occur. Research has also demonstrated that oxytocin can decrease anxiety and protect against stress, particularly in combination with social support.[21]
  • Due to its similarity to vasopressin, it can reduce the excretion of urine slightly. In several species, oxytocin can stimulate sodium excretion from the kidneys (natriuresis), and, in humans, high doses can result in hyponatremia.
  • Oxytocin and oxytocin receptors are also found in the heart in some rodents, and the hormone may play a role in the embryonal development of the heart by promotingcardiomyocyte differentiation.[22][23] However, the absence of either oxytocin or its receptor in knockout mice has not been reported to produce cardiac insufficiencies.[15]
  • Modulation of hypothalamic-pituitary-adrenal axis activity: Oxytocin, under certain circumstances, indirectly inhibits release of adrenocorticotropic hormone and cortisol and, in those situations, may be considered an antagonist of vasopressin.[24]
  • Autism: Oxytocin may play a role in autism and may be an effective treatment for autism‘s repetitive and affiliative behaviors.[25] Oxytocin treatments also resulted in an increased retention of affective speech in adults with autism.[26] Two related studies in adults, in 2003 and 2007, found oxytocin decreased repetitive behaviors and improved interpretation of emotions. More recently, intranasal administration of oxytocin was found to increase emotion recognition in children as young as 12 who are diagnosed with autism spectrum disorders.[27] Oxytocin has also been implicated in the etiology of autism, with one report suggesting autism is correlated with genomic deletion of the gene containing the oxytocin receptor gene (OXTR). Studies involving Caucasian and Finnish samples and Chinese Han families provide support for the relationship of OXTR with autism.[26][28] Autism may also be associated with an aberrant methylation of OXTR.[26] After treatment with inhaled oxytocin, autistic patients exhibit more appropriate social behavior.[29] While this research suggests some promise, further clinical trials of oxytocin are required to demonstrate potential benefit and side effects in the treatment of autism. As such, researchers do not recommend use of oxytocin as a treatment for autism outside of clinical trials.[30]
  • Nasally administered oxytocin has also been reported to reduce fear, possibly by inhibiting the amygdala (which is thought to be responsible for fear responses).[31] Indeed, studies in rodents have shown oxytocin can efficiently inhibit fear responses by activating an inhibitory circuit within the amygdala.[32][33] Some researchers have argued oxytocin has a general enhancing effect on all social emotions, since intranasal administration of oxytocin also increases envy and Schadenfreude.[34]
  • Trust is increased by oxytocin.[35][36][37] Disclosure of emotional events is a sign of trust in humans. When recounting a negative event, humans who receive intranasaloxytocin share more emotional details and stories with more emotional significance.[36] Humans also find faces more trustworthy after receiving intranasal oxytocin. In a study, participants who received intranasal oxytocin viewed photographs of human faces with neutral expressions and found them to be more trustworthy than those who did not receive oxytocin.[35] This may be because oxytocin reduces the fear of social betrayal in humans.[38] Even after experiencing social alienation by being excluded from a conversation, humans who received oxytocin scored higher in trust on the Revised NEO Personality Inventory.[37] Moreover, in a risky investment game, experimental subjects given nasally administered oxytocin displayed “the highest level of trust” twice as often as the control group. Subjects who were told they were interacting with a computer showed no such reaction, leading to the conclusion that oxytocin was not merely affecting risk aversion.[39] When there is a reason to be distrustful, such as experiencing betrayal, differing reactions are associated with oxytocin receptor gene (OXTR) differences. Those with the CT haplotype experience a stronger reaction, in the form of anger, to betrayal.[40]
  • Oxytocin affects social distance between adult males and females, and may be responsible at least in part for romantic attraction and subsequent monogamous pair bonding. An oxytocin nasal spray caused men in a monogamous relationship, but not single men, to increase the distance between themselves and an attractive woman during a first encounter by 10 to 15 centimeters. The researchers suggested that oxytocin may help promote fidelity within monogamous relationships.[41] For this reason, it is sometimes referred to as the “bonding hormone”. There is some evidence that oxytocin promotes ethnocentric behavior, incorporating the trust and empathy of in-groups with their suspicion and rejection of outsiders.[16] Furthermore, genetic differences in the oxytocin receptor gene (OXTR) have been associated with maladaptive social traits such as aggressive behaviour.[42]
  • Affecting generosity by increasing empathy during perspective taking: In a neuroeconomics experiment, intranasal oxytocin increased generosity in the Ultimatum Game by 80%, but had no effect in the Dictator Game that measures altruism. Perspective-taking is not required in the Dictator Game, but the researchers in this experiment explicitly induced perspective-taking in the Ultimatum Game by not identifying to participants into which role they would be placed.[43] Serious methodological questions have arisen, however, with regard to the role of oxytocin in trust and generosity.[44]
Empathy in healthy males has been shown to be increased after intranasal oxytocin[45][46] This is most likely due to the effect of oxytocin in enhancing eye gaze.[47] There is some discussion about which aspect of empathy oxytocin might alter – for example, cognitive vs. emotional empathy.[48]
  • Certain learning and memory functions are impaired by centrally administered oxytocin.[49] Also, systemic oxytocin administration can impair memory retrieval in certain aversive memory tasks.[50] Interestingly, oxytocin does seem to facilitate learning and memory specifically for social information. Healthy males administered intranasal oxytocin show improved memory for human faces, in particular happy faces.[51][52] They also show improved recognition for positive social cues over threatening social cues[53][54] and improved recognition of fear.[55]
  • Sexual activity: The relationship between oxytocin and human sexual response is unclear. At least two uncontrolled studies have found increases in plasma oxytocin at orgasm – in both men and women.[56][57] Plasma oxytocin levels are notably increased around the time of self-stimulated orgasm and are still higher than baseline when measured five minutes after self arousal.[56] The authors of one of these studies speculated that oxytocin’s effects on muscle contractibility may facilitate sperm and egg transport.[56]
In a study measuring oxytocin serum levels in women before and after sexual stimulation, the author suggests it serves an important role in sexual arousal. This study found genital tract stimulation resulted in increased oxytocin immediately after orgasm.[58] Another study reported increases of oxytocin during sexual arousal could be in response to nipple/areola, genital, and/or genital tract stimulation as confirmed in other mammals.[59] Murphy et al. (1987), studying men, found oxytocin levels were raised throughout sexual arousal with no acute increase at orgasm.[60] A more recent study of men found an increase in plasma oxytocin immediately after orgasm, but only in a portion of their sample that did not reach statistical significance. The authors noted these changes “may simply reflect contractile properties on reproductive tissue”.[61]
  • Bonding: In the prairie vole, oxytocin released into the brain of the female during sexual activity is important for forming a monogamous pair bond with her sexual partner. Vasopressin appears to have a similar effect in males.[62] Oxytocin has a role in social behaviors in many species, so it likely also does in humans. In a 2003 study, both humans and dog oxytocin levels in the blood rose after five to 24 minutes of a petting session. This possibly plays a role in the emotional bonding between humans and dogs.[63]
  • Maternal behavior: Female rats given oxytocin antagonists after giving birth do not exhibit typical maternal behavior.[64] By contrast, virgin female sheep show maternal behavior toward foreign lambs upon cerebrospinal fluid infusion of oxytocin, which they would not do otherwise.[65] Oxytocin is involved in the initiation of maternal behavior, not its maintenance; for example, it is higher in mothers after they interact with unfamiliar children rather than their own.[66]
  • Drug interactions: According to some studies in animals, oxytocin inhibits the development of tolerance to various addictive drugs (opiates, cocaine, alcohol), and reduceswithdrawal symptoms.[67] MDMA (ecstasy) may increase feelings of love, empathy, and connection to others by stimulating oxytocin activity primarily via activation of serotonin5-HT1A receptors, if initial studies in animals apply to humans.[68] The anxiolytic Buspar (buspirone) may produce some of its effects via 5-HT1A receptor-induced oxytocin stimulation as well.[69][70]
  • Preparing fetal neurons for delivery: Crossing the placenta, maternal oxytocin reaches the fetal brain and induces a switch in the action of neurotransmitter GABA from excitatory to inhibitory on fetal cortical neurons. This silences the fetal brain for the period of delivery and reduces its vulnerability to hypoxic damage.[71]
  • Romantic attachment: In some studies, high levels of plasma oxytocin have been correlated with romantic attachment. For example, if a couple is separated for a long period of time, anxiety can increase due to the lack of physical affection. Oxytocin may aid romantically attached couples by decreasing their feelings of anxiety when they are separated.[20]
  • Feeding: Recent evidence has suggested that oxytocin neurons in the para-ventricular hypothalamus in the brain may play a key role in suppressing appetite under normal conditions and that other hypothalamic neurons may trigger eating via inhibition of these oxytocin neurons. This population of oxytocin neurons are absent in Prader-Willi syndrome, a genetic disorder that leads to uncontrollable feeding and obesity, and may play a key role in its pathophysiology.[72]
  • Group-serving dishonesty/deception: In a carefully controlled study exploring the biological roots of immoral behavior, oxytocin was shown to promote dishonesty when the outcome favored the group to which an individual belonged instead of just the individual.[73]
  • Intergroup bonding: Oxytocin can increase positive attitudes, such as bonding, toward individuals with similar characteristics, who then become classified as “in-group” members, whereas individuals who are dissimilar become classified as “out-group” members. Race can be used as an example of in-group and out-group tendencies because society often categorizes individuals into groups based on race (Caucasian, African American, Latino, etc.). One study that examined race and empathy found that participants receiving nasally administered oxytocin had stronger reactions to pictures of in-group members making pained faces than to pictures of out-group members with the same expression.[74] This shows that oxytocin may be implicated in our ability to empathize with individuals of different races and could potentially translate into willingness to help individuals in pain or stressful situations. Moreover, individuals of one race may be more inclined to help individuals of the same race than individuals of another race when they are experiencing pain. Oxytocin has also been implicated in lying when lying would prove beneficial to other in-group members. In a study where such a relationship was examined, it was found that when individuals were administered oxytocin, rates of dishonesty in the participants’ responses increased for their in-group members when a beneficial outcome for their group was expected.[75] Both of these examples show the tendency to act in ways that benefit people with which one feels is part of their social group, or in-group. Oxytocin is not only correlated with the preferences of individuals to associate with members of their own group, but it is also evident during conflicts between members of different groups. During conflict, individuals receiving nasally administered oxytocin demonstrate more frequent defense-motivated responses toward in-group members than out-group members. Further, oxytocin was correlated with participant desire to protect vulnerable in-group members, despite that individual’s attachment to the conflict.[76] Similarly, it has been demonstrated that when oxytocin is administered, individuals alter their subjective preferences in order to align with in-group ideals over out-group ideals.[77] These studies demonstrate that oxytocin is associated with intergroup dynamics. Further, oxytocin influences the responses of individuals in a particular group to those of another group. The in-group bias is evident in smaller groups; however, it can also be extended to groups as large as one’s entire country leading toward a tendency of strong national zeal. A study done in the Netherlands showed that oxytocin increased the in-group favoritism of their nation while decreasing acceptance of members of other ethnicities and foreigners.[16] People also show more affection for their country’s flag while remaining indifferent to other cultural objects when exposed to oxytocin.[78] It has thus been hypothesized that this hormone may be a factor in xenophobic tendencies secondary to this effect. Thus, oxytocin appears to affect individuals at an international level where the in-group becomes a specific “home” country and the out-group grows to include all other countries.

risk perception

Risk as Analysis and Risk as Feelings: Some Thoughts about Affect, Reason, Risk, and Rationality

Paul Slovic,

Melissa L. Finucane,

Ellen Peters,

Donald G. MacGregor

Risk as Analysis and Risk as Feelings: Some Thoughts about Affect, Reason, Risk, and Rationality

  • Paul Slovic,

  • Melissa L. Finucane,

  • Ellen Peters,

  • Donald G. MacGregor

The nucleus accumbens

The nucleus accumbens (NAc or NAcc), also known as the accumbens nucleus or as the nucleus accumbens septi (Latin fornucleus adjacent to the septum) is a region in the basal forebrain rostral to the preoptic area of the hypothalamus.[1] The nucleus accumbens and the olfactory tubercle collectively form the ventral striatum, which is part of […]

The nucleus accumbens (NAc or NAcc), also known as the accumbens nucleus or as the nucleus accumbens septi (Latin fornucleus adjacent to the septum) is a region in the basal forebrain rostral to the preoptic area of the hypothalamus.[1] The nucleus accumbens and the olfactory tubercle collectively form the ventral striatum, which is part of the basal ganglia.[2] Each cerebral hemisphere has its own nucleus accumbens, which can be divided into two structures: the nucleus accumbens core and the nucleus accumbens shell. These substructures have different morphology and functions.

Different NAcc subregions (core vs shell) and neuron subpopulations within each region (D1-type vs D2-type medium spiny neurons) are responsible for different cognitive functions.[3][4] As a whole, the nucleus accumbens has a significant role in the cognitive processing of aversion, motivation, pleasure, reward and reinforcement learning;[5][6][7] hence, it has a significant role inaddiction.[6][7] It plays a lesser role in processing fear (a form of aversion), impulsivity, and the placebo effect.[8][9][10] It is involved in the encoding of new motor programs as well.[6]

Major inputs to the nucleus accumbens include the prefrontal cortex, basolateral amygdala, and dopaminergic neurons located in the ventral tegmental area (VTA), which connect via the mesolimbic pathway. Thus the nucleus accumbens is often described as one part of a cortico–basal ganglia–thalamic loop.[11]

Dopaminergic input from the VTA modulate the activity of neurons within the nucleus accumbens. These neurons are activated directly or indirectly by euphoriant drugs (e.g.,amphetamine, opiates, etc.) and by participating in rewarding experiences (e.g., sex, music, exercise, etc.).[12][13]

Another major source of input comes from the CA1 and ventral subiculum of the hippocampus to the dorsomedial area of the nucleus accumbens. The neurons of the hippocampus have a noteworthy correlation to slight depolarizations of cells in the nucleus accumbens, which makes them more positive and therefore more excitable. The correlated cells of these excited states of the medium spiny neurons in the nucleus accumbens are shared equally between the subiculum and CA1. The subiculum neurons are found to hyperpolarize (increase negativity) while the CA1 neurons “ripple” (fire > 50 Hz) in order to accomplish this priming.[14]

The nucleus accumbens is one of the few regions that receive histaminergic projections from the tuberomammillary nucleus (the sole source of histamine neurons in the brain).[15]


The output neurons of the nucleus accumbens send axon projections to the basal ganglia and the ventral analog of the globus pallidus, known as the ventral pallidum (VP). The VP, in turn, projects to the medial dorsal nucleus of the dorsal thalamus, which projects to the prefrontal cortex as well as the striatum. Other efferents from the nucleus accumbens include connections with the tail of the ventral tegmental area,[16] substantia nigra, and the reticular formation of the pons.[1]


Dopamine: Dopamine is related to recreational drugs including amphetamines, cocaine, and morphine, which increase extracellular levels of dopamine in both the NAc shell and the NAc core, but the effect of these increases is more pronounced in the shell. Only amphetamine at high levels increases extracellular levels of dopamine to similar levels in both the shell and the core. All of this points to a ‘functional heterogeneity’ in the nucleus accumbens between the shell region and the core region.[26] Similarly to drug rewards, non-drug rewards also increase levels of extracellular dopamine in the NAc shell, but drug induced DA increase is more resilient to habituation when exposed repeatedly to drug-stimuli, unlike non-drug rewarding stimuli induced dopamine increases, which do succumb to habituation. Recent[when?] studies have shown that the repeated influence of drug-inducing DA projection has an abnormal strengthening effect on stimulus-drug associations and increases the drug-reward stimuli’s resistance to extinction. This may be a contributing factor to addiction. This effect was more pronounced in the NAc shell than in the NAc core.[19][27]

Phenethylamine and tyramine: Phenethylamine and tyramine are trace amine compounds which are synthesized in several types of CNS neurons, including all dopamine neurons.[28] Specifically, these neurotransmitters act within the dopaminergic inputs to the NAcc. These substances regulate the presynaptic release of dopamine through their interactions with VMAT2 and TAAR1, analogous to amphetamine.

Glucocorticoids and dopamine: Glucocorticoid receptors are the only corticosteroid receptors in the nucleus accumbens shell. L-DOPA, steroids, and specifically glucocorticoids are currently known to be the only known endogenous compounds that can induce psychotic problems, so understanding the hormonal control over dopaminergic projections with regards to glucocorticoid receptors could lead to new treatments for psychotic symptoms. A recent study demonstrated that suppression of the glucocorticoid receptors led to a decrease in the release of dopamine, which may lead to future research involving anti-glucocorticoid drugs to potentially relieve psychotic symptoms.[29]

Glucocorticoids (GCs) are a class of corticosteroids, which are a class of steroid hormones. Glucocorticoids are corticosteroids that bind to the glucocorticoid receptor (GR),[1] that is present in almost every vertebrate animal cell. The name glucocorticoid (glucose +cortex + steroid) is composed from its role in regulation of glucose metabolisms synthesis in the adrenal cortex, and its steroidalstructure (see structure to the right). A less common synonym is glucocorticosteroid.

GCs are part of the feedback mechanism in the immune system which reduces certain aspects of immune function, such as reduction of inflammation. They are therefore used in medicine to treat diseases caused by an overactive immune system, such as allergies, asthma, autoimmune diseases, and sepsis. GCs have many diverse (pleiotropic) effects, including potentially harmful side effects, and as a result are rarely sold over the counter.[2] They also interfere with some of the abnormal mechanisms in cancer cells, so they are used in high doses to treat cancer. This includes: inhibitory effects on lymphocyte proliferation as in the treatment of lymphomas and leukemias; and the mitigation of side effects of anticancer drugs.

GCs affect cells by binding to the glucocorticoid receptor (GR). The activated GR complex, in turn, up-regulates the expression of anti-inflammatory proteins in the nucleus (a process known as transactivation) and represses the expression of proinflammatory proteins in the cytosol by preventing the translocation of other transcription factors from the cytosol into the nucleus (transrepression).[2]

Glucocorticoids are distinguished from mineralocorticoids and sex steroids by their specific receptors, target cells, and effects. In technical terms, “corticosteroid” refers to both glucocorticoids and mineralocorticoids (as both are mimics of hormones produced by the adrenal cortex), but is often used as a synonym for “glucocorticoid.” Glucocorticoids are chiefly produced in the zona fasciculataof the adrenal cortex, whereas mineralocorticoids are synthesized in the zona glomerulosa.

Cortisol (or hydrocortisone) is the most important human glucocorticoid. It is essential for life, and it regulates or supports a variety of important cardiovascular, metabolic, immunologic, and homeostatic functions. Various synthetic glucocorticoids are available; these are used either as replacement therapy in glucocorticoid deficiency or to suppress the immune system.

Glucocorticoids act on the hippocampus, amygdala, and frontal lobes. Along with adrenaline, these enhance the formation of flashbulb memories of events associated with strong emotions, both positive and negative.[5] This has been confirmed in studies, whereby blockade of either glucocorticoids or noradrenaline activity impaired the recall of emotionally relevant information. Additional sources have shown subjects whose fear learning was accompanied by high cortisol levels had better consolidation of this memory (this effect was more important in men). The effect that glucocorticoids have on memory may be due to damage specifically to the CA1 area of the hippocampal formation. In multiple animal studies, prolonged stress (causing prolonged increases in glucocorticoid levels) have shown destruction of the neurons in this area of the brain, which has been connected to memory performance.[6][7][8]

Glucocorticoids have also been shown to have a significant impact on vigilance (attention deficit disorder) and cognition (memory). This appears to follow the Yerkes-Dodson curve, as studies have shown circulating levels of glucocorticoids vs. memory performance follow an upside-down U pattern, much like the Yerkes-Dodson curve. For example, long-term potentiation (LTP; the process of forming long-term memories) is optimal when glucocorticoid levels are mildly elevated, whereas significant decreases of LTP are observed after adrenalectomy (low-GC state) or after exogenous glucocorticoid administration (high-GC state). Elevated levels of glucocorticoids enhance memory for emotionally arousing events, but lead more often than not to poor memory for material unrelated to the source of stress/emotional arousal.[9] In contrast to the dose-dependent enhancing effects of glucocorticoids on memory consolidation, these stress hormones have been shown to inhibit the retrieval of already stored information.[10] Long-term exposure to glucocorticoid medications, such as asthma and anti-inflammatory medication, has been shown to create deficits in memory and attention both during and, to a lesser extent, after treatment,[11][12] a condition known as “steroid dementia.”[13]

GABA: A recent study on rats that used GABA agonists and antagonists indicated that GABAA receptors in the NAc shell have inhibitory control on turning behavior influenced by dopamine, and GABAB receptors have inhibitory control over turning behavior mediated by acetylcholine.[19][30]

Glutamate: Studies have shown that local blockade of glutamatergic NMDA receptors in the NAcc core impaired spatial learning.[31] Another study demonstrated that both NMDA and AMPA (both glutamate receptors) play important roles in regulating instrumental learning.[32]

Serotonin (5-HT): Overall, 5-HT synapses are more abundant and have a greater number of synaptic contacts in the NAc shell than in the core. They are also larger and thicker, and contain more large dense core vesicles than their counterparts in the core.

Reward and reinforcement

The nucleus accumbens, being one part of the reward system, plays an important role in processing rewarding stimuli, reinforcing stimuli (e.g., food and water), and those which are both rewarding and reinforcing (addictive drugs, sex, and exercise).[6][33] The nucleus accumbens is selectively activated during the perception of pleasant, emotionally arousing pictures and during mental imagery of pleasant, emotional scenes.[34][35] A 2005 study found that it is involved in the regulation of emotions induced by music,[36]perhaps consequent to its role in mediating dopamine release. The nucleus accumbens plays a role in rhythmic timing and is considered to be of central importance to the limbic-motor interface (Mogensen).[citation needed]

In the 1950s, James Olds and Peter Milner implanted electrodes into the septal area of the rat and found that the rat chose to press a lever which stimulated it. It continued to prefer this even over stopping to eat or drink. This suggests that the area is the “pleasure center” of the brain and is involved in reinforcement learning.[37] In rats, stimulation of the ventral tegmental area causes the release of dopamine in the nucleus accumbens much in the same way as addictive drugs and natural reinforcers, such as water or food, initiate the release of dopamine in the nucleus accumbens.[38] The same results have been seen in human subjects in functional imaging studies. For example, increased dopamine concentration is seen in the extracellular fluid of the nucleus accumbens when subjects believed they were being given money[citation needed], and increased activation (i.e., increased fMRI BOLD signal-change) was observed among heterosexual males viewing pictures of attractive women.[39]


Activation of D1-type MSNs in the nucleus accumbens is involved in reward, whereas the activation of D2-type MSNs in the nucleus accumbens promotes aversion.[4]

Maternal behavior

An fMRI study conducted in 2005 found that when mother rats were in the presence of their pups the regions of the brain involved in reinforcement, including the nucleus accumbens, were highly active.[40] Levels of dopamine increase in the nucleus accumbens during maternal behavior, while lesions in this area upset maternal behavior.[41] When women are presented pictures of unrelated infants, fMRIs show increased brain activity in the nucleus accumbens and adjacent caudate nucleus, proportionate to the degree to which the women find these infants “cute”.[42]

Placebo effect

Activation of the NAcc has been shown to occur in the anticipation of effectiveness of a drug when a user is given a placebo, indicating a contributing role of the nucleus accumbens in the placebo effect.[9][52]

A smile

A smile is a facial expression formed primarily by flexing the muscles at the sides of the mouth.[1] Some smiles include a contraction of the muscles at the corner of the eyes, an action known as a “Duchenne smile”. Smiles performed without the eye contraction can be perceived as “fake”. Among humans, smiling is an […]

A smile is a facial expression formed primarily by flexing the muscles at the sides of the mouth.[1] Some smiles include a contraction of the muscles at the corner of the eyes, an action known as a “Duchenne smile”. Smiles performed without the eye contraction can be perceived as “fake”.

Among humans, smiling is an expression denoting pleasure, sociability, happiness, or amusement. It is distinct from a similar but usually involuntary expression of anxiety known as a grimace. Although cross-cultural studies have shown that smiling is a means of communication throughout the world,[2] there are large differences between different cultures, with some using smiles to convey confusion or embarrassment.

A smile seems to have a favorable influence upon others and makes one likable and more approachable.[3] In the social context, smiling and laughter have different functions in the order of sequence in social situations:

  • Smiling is not a pre-laughing device and is a common pattern for paving the way to laughter;
  • Smiling can be used as a response to laughter in the previous turn.[4]

Smiling is a signaling system that evolved from a need to communicate information of many different forms. One of these is advertisement of sexual interest. Female smiles are appealing to heterosexual males, increasing physical attractiveness and enhancing sex appeal. However, recent research indicates a man’s smile may or may not be most effective in attracting heterosexual women, and that facial expressions such as pride or even shame might be more effective. The researchers ignored the role of smiles in other sexual preferences.[5]

Cultural differences

A Smiling boy from Bangladesh.

While smiling is perceived as a positive emotion most of the time, there are many cultures that perceive smiling as a negative expression and consider it unwelcoming. Too much smiling can be viewed as a sign of shallowness or dishonesty.[6] In other parts of Asia, people may smile when they are embarrassed or in emotional pain. Some people may smile at others to indicate a friendly greeting. A smile may be reserved for close friends and family members. Many people in the former Soviet Union area consider smiling at strangers in public to be unusual and even suspicious behavior.

While conducting research on the physiology of facial expressions in the mid-19th century, French neurologist Guillaume Duchenneidentified two distinct types of smiles. A Duchenne smile involves contraction of both the zygomatic major muscle (which raises the corners of the mouth) and the orbicularis oculi muscle (which raises the cheeks and forms crow’s feet around the eyes).[9]

A non-Duchenne smile involves only the zygomatic major muscle.[10] “Research with adults initially indicated that joy was indexed by generic smiling, any smiling involving the raising of the lip corners by the zygomatic major…. More recent research suggests that smiling in which the muscle around the eye contracts, raising the cheeks high (Duchenne smiling), is uniquely associated with positive emotion.”[11]

The Pan Am smile, also known as the “Botox smile”, is the name given to a fake smile, in which only the zygomatic major muscle is voluntarily contracted to show politeness. It is named after the now defunct airline Pan American World Airways, whose flight attendants would always flash every passenger the same perfunctory smile.[12] Botox was introduced for cosmetic use in 2002.[13] Chronic use of Botox injections to deal with eye wrinkle can result in the paralysis of the small muscles around the eyes, preventing the appearance of a Duchenne smile.

In animals

In animals, the exposure of teeth, which may bear a resemblance to a smile and imply happiness, often conveys other signals. The baring of teeth is often used as a threat or warning display—known as a snarl—or a sign of submission. For chimpanzees, it can also be a sign of fear. However, not all animal displays of teeth convey negative acts or emotions. For example, Barbary macaques demonstrate an open mouth display as a sign of playfulness which likely has similar roots and purposes as the human smile.[14]

Appraisal theory

Appraisal theory is the theory in psychology that emotions are extracted from our evaluations (appraisals or estimates) of events that cause specific reactions in different people. Essentially, our appraisal of a situation causes an emotional, or affective, response that is going to be based on that appraisal. An example of this is going on a […]

Appraisal theory is the theory in psychology that emotions are extracted from our evaluations (appraisals or estimates) of events that cause specific reactions in different people. Essentially, our appraisal of a situation causes an emotional, or affective, response that is going to be based on that appraisal. An example of this is going on a first date. If the date is perceived as positive, one might feel happiness, joy, giddiness, excitement, and/or anticipation, because they have appraised this event as one that could have positive long-term effects, i.e. starting a new relationship, engagement, or even marriage. On the other hand, if the date is perceived negatively, then our emotions, as a result, might include dejection, sadness, emptiness, or fear. (Scherer et al., 2001)[1] Reasoning and understanding of one’s emotional reaction becomes important for future appraisals as well. The important aspect of the appraisal theory is that it accounts for individual variances of emotional reactions to the same event.[2]

Appraisal theories of emotion are theories that state that emotions result from people’s interpretations and explanations of their circumstances even in the absence of physiological arousal (Aronson, 2005).[3] There are two basic approaches; the structural approach and process model. These models both provide an explanation for the appraisal of emotions and explain in different ways how emotions can develop. In the absence of physiological arousal we decide how to feel about a situation after we have interpreted and explained the phenomena. Thus the sequence of events is as follows: event, thinking, and simultaneous events of arousal and emotion. Social psychologists have used this theory to explain and predict coping mechanisms and people’s patterns of emotionality. By contrast, for example, personality psychology studies emotions as a function of a person’s personality, and thus does not take into account the person’s appraisal, or cognitive response, to a situation.

The main controversy surrounding these theories argues that emotions cannot happen without physiological arousal.

The question studied under appraisal theories is why people react to things differently. Even when presented with the same, or a similar situation all people will react in slightly different ways based on their perception of the situation. These perceptions elicit various emotions that are specific to each person.

Richard S. Lazarus

Richard S. Lazarus (March 3, 1922 – November 24, 2002[1]) was a psychologist who began rising to prominence in the 1960s, when behaviorists like B. F. Skinner held sway over psychology and explanations for human behavior were often pared down to rudimentary motives like reward and punishment. A Review of General Psychology survey, published in […]

Richard S. Lazarus (March 3, 1922 – November 24, 2002[1]) was a psychologist who began rising to prominence in the 1960s, when behaviorists like B. F. Skinner held sway over psychology and explanations for human behavior were often pared down to rudimentary motives like reward and punishment. A Review of General Psychology survey, published in 2002, ranked Lazarus as the 80th most cited psychologist of the 20th century.[2]

Lazarus was a professor in the Department of Psychology at the University of California, Berkeley who was named by American Psychologist as one of the most influential psychologists. He was a pioneer in the study of emotion and stress, especially their relation to cognition.

He was well renowned for his theory of cognitive-mediational theory within emotion.

Lazarus was an unabashed promoter of the importance of emotion, especially what he described as the marriage between emotion and thought. His views put him at odds not only with behaviorism but also with a movement that began toward the end of his career: attempts to explain all human behavior by looking at the structure of the brain.[citation needed] He was very opposed to reductionist approaches to understanding human behavior.

At the heart of Lazarus’s theory was what he called appraisal. Before emotion occurs, he argued, people make an automatic, often unconscious, assessment of what is happening and what it may mean for them or those they care about. From that perspective, emotion becomes not just rational but a necessary component of survival.

Lazarus worked on topics such as hope and gratitude. He was perhaps best known for his work on coping, gaining attention for studies that showed that patients who engaged in denial about the seriousness of their situation did better than those who were more “realistic.” He also found that stress often had less to do with a person’s actual situation than with how the person perceived the strength of his own resources.

How to learn

Published on Nov 20, 2013 Chris Lonsdale is Managing Director of Chris Lonsdale & Associates, a company established to catalyse breakthrough performance for individuals and senior teams. In addition, he has also developed a unique and integrated approach to learning that gives people the means to acquire language or complex technical knowledge in short periods […]

Published on Nov 20, 2013

Chris Lonsdale is Managing Director of Chris Lonsdale & Associates, a company established to catalyse breakthrough performance for individuals and senior teams. In addition, he has also developed a unique and integrated approach to learning that gives people the means to acquire language or complex technical knowledge in short periods of time.

Jan-21-2014 Update. The video transcripts are now available via the following links:

English Only:

English + Chinese Translation:


THE EXPRESSION OF THE EMOTIONS IN MAN AND ANIMALS By Charles Darwin With Photographic And Other Illustrations New York D. Appleton And Company 1899 ON THE EXPRESSION OF THE EMOTIONS IN MAN AND ANIMALS. INTRODUCTION. MANY works have been written on Expression, but a greater number on Physiognomy,—that is, on the recognition of character through […]


By Charles Darwin

With Photographic And Other Illustrations

New York

D. Appleton And Company




MANY works have been written on Expression, but a greater number on Physiognomy,—that is, on the recognition of character through the study of the permanent form of the features. With this latter subject I am not here concerned. The older treatises,[1] which I have consulted, have been of little or no service to me. The famous ‘Conferences’[2] of the painter Le Brun, published in 1667, is the best known ancient work, and contains some good remarks. Another somewhat old essay, namely, the ‘Discours,’ delivered 1774-1782, by the well-known Dutch anatomist Camper,[3] can hardly be considered as having made any marked advance in the subject. The following works, on the contrary, deserve the fullest consideration.

Sir Charles Bell, so illustrious for his discoveries in physiology, published in 1806 the first edition, and in the third edition of his ‘Anatomy and Philosophy of Expression.’[4] He may with justice be said, not only to have laid the foundations of the subject as a branch of science, but to have built up a noble structure. His work is in every way deeply interesting; it includes graphic descriptions of the various emotions, and is admirably illustrated. It is generally admitted that his service consists chiefly in having shown the intimate relation which exists between the movements of expression and those of respiration. One of the most important points, small as it may at first appear, is that the muscles round the eyes are involuntarily contracted during violent expiratory efforts, in order to protect these delicate organs from the pressure of the blood. This fact, which has been fully investigated for me with the greatest kindness by Professors Donders of Utrecht, throws, as we shall hereafter see, a flood of light on several of the most important expressions of the human countenance. The merits of Sir C. Bell’s work have been undervalued or quite ignored by several foreign writers, but have been fully admitted by some, for instance by M. Lemoine,[5] who with great justice says:—”Le livre de Ch. Bell devrait etre medite par quiconque essaye de faire parler le visage de l’homme, par les philosophes aussi bien que par les artistes, car, sous une apparence plus legere et sous le pretexte de l’esthetique, c’est un des plus beaux monuments de la science des rapports du physique et du moral.”

From reasons which will presently be assigned, Sir C. Bell did not attempt to follow out his views as far as they might have been carried. He does not try to explain why different muscles are brought into action under different emotions; why, for instance, the inner ends of the eyebrows are raised, and the corners of the mouth depressed, by a person suffering from grief or anxiety.

In 1807 M. Moreau edited an edition of Lavater on Physiognomy,[6] in which he incorporated several of his own essays, containing excellent descriptions of the movements of the facial muscles, together with many valuable remarks. He throws, however, very little light on the philosophy of the subject. For instance, M. Moreau, in speaking of the act of frowning, that is, of the contraction of the muscle called by French writers the soucilier (corrigator supercilii), remarks with truth:—”Cette action des sourciliers est un des symptomes les plus tranches de l’expression des affections penibles ou concentrees.” He then adds that these muscles, from their attachment and position, are fitted “a resserrer, a concentrer les principaux traits de la face, comme il convient dans toutes ces passions vraiment oppressives ou profondes, dans ces affections dont le sentiment semble porter l’organisation a revenir sur elle-meme, a se contracter et a s’amoindrir, comme pour offrir moins de prise et de surface a des impressions redoutables ou importunes.” He who thinks that remarks of this kind throw any light on the meaning or origin of the different expressions, takes a very different view of the subject to what I do.

The earliest edition of this work, referred to in the preface to the edition of 1820 in ten volumes, as containing the observations of M. Moreau, is said to have been published in 1807; and I have no doubt that this is correct, because the ‘Notice sur Lavater’ at the commencement of volume i. is dated April 13, 1806. In some bibliographical works, however, the date of 1805—1809 is given, but it seems impossible that 1805 can be correct. Dr. Duchenne remarks (‘Mecanisme de la Physionomie Humaine,’-8vo edit. 1862, p. 5, and ‘Archives Generales de Medecine,’ Jan. et Fev. 1862) that M. Moreau “a compose pour son ouvrage un article important,” &c., in the year 1805; and I find in volume i. of the edition of 1820 passages bearing the dates of December 12, 1805, and another January 5, 1806, besides that of April 13, 1806, above referred to. In consequence of some of these passages having thus been COMPOSED in 1805, Dr. Duchenne assigns to M. Moreau the priority over Sir C. Bell, whose work, as we have seen, was published in 1806. This is a very unusual manner of determining the priority of scientific works; but such questions are of extremely little importance in comparison with their relative merits. The passages above quoted from M. Moreau and from Le Brun are taken in this and all other cases from the edition of 1820 of Lavater, tom. iv. p. 228, and tom. ix. p. 279. In the above passage there is but a slight, if any, advance in the philosophy of the subject, beyond that reached by the painter Le Brun, who, in 1667, in describing the expression of fright, says:—”Le sourcil qui est abaisse d’un cote et eleve de l’autre, fait voir que la partie elevee semble le vouloir joindre au cerveau pour le garantir du mal que l’ame apercoit, et le cote qui est abaisse et qui parait enfle,—nous fait trouver dans cet etat par les esprits qui viennent du cerveau en abondance, comme polir couvrir l’aine et la defendre du mal qu’elle craint; la bouche fort ouverte fait voir le saisissement du coeur, par le sang qui se retire vers lui, ce qui l’oblige, voulant respirer, a faire un effort qui est cause que la bouche s’ouvre extremement, et qui, lorsqu’il passe par les organes de la voix, forme un son qui n’est point articule; que si les muscles et les veines paraissent enfles, ce n’est que par les esprits que le cerveau envoie en ces parties-la.” I have thought the foregoing sentences worth quoting, as specimens of the surprising nonsense which has been written on the subject.

‘The Physiology or Mechanism of Blushing,’ by Dr. Burgess, appeared in 1839, and to this work I shall frequently refer in my thirteenth Chapter.

In 1862 Dr. Duchenne published two editions, in folio and octavo, of his ‘Mecanisme de la Physionomie Humaine,’ in which he analyses by means of electricity, and illustrates by magnificent photographs, the movements of the facial muscles. He has generously permitted me to copy as many of his photographs as I desired. His works have been spoken lightly of, or quite passed over, by some of his countrymen. It is possible that Dr. Duchenne may have exaggerated the importance of the contraction of single muscles in giving expression; for, owing to the intimate manner in which the muscles are connected, as may be seen in Henle’s anatomical drawings[7]—the best I believe ever published it is difficult to believe in their separate action. Nevertheless, it is manifest that Dr. Duchenne clearly apprehended this and other sources of error, and as it is known that he was eminently successful in elucidating the physiology of the muscles of the hand by the aid of electricity, it is probable that he is generally in the right about the muscles of the face. In my opinion, Dr. Duchenne has greatly advanced the subject by his treatment of it. No one has more carefully studied the contraction of each separate muscle, and the consequent furrows produced on the skin. He has also, and this is a very important service, shown which muscles are least under the separate control of the will. He enters very little into theoretical considerations, and seldom attempts to explain why certain muscles and not others contract under the influence of certain emotions. A distinguished French anatomist, Pierre Gratiolet, gave a course of lectures on Expression at the Sorbonne, and his notes were published (1865) after his death, under the title of ‘De la Physionomie et des Mouvements d’Expression.’ This is a very interesting work, full of valuable observations. His theory is rather complex, and, as far as it can be given in a single sentence (p. 65), is as follows:—”Il resulte, de tous les faits que j’ai rappeles, que les sens, l’imagination et la pensee ellememe, si elevee, si abstraite qu’on la suppose, ne peuvent s’exercer sans eveiller un sentiment correlatif, et que ce sentiment se traduit directement, sympathiquement, symboliquement ou metaphoriquement, dans toutes les spheres des organs exterieurs, qui la racontent tous, suivant leur mode d’action propre, comme si chacun d’eux avait ete directement affecte.”

Gratiolet appears to overlook inherited habit, and even to some extent habit in the individual; and therefore he fails, as it seems to me, to give the right explanation, or any explanation at all, of many gestures and expressions. As an illustration of what he calls symbolic movements, I will quote his remarks (p. 37), taken from M. Chevreul, on a man playing at billiards. “Si une bille devie legerement de la direction que le joueur pretend zlui imprimer, ne l’avez-vous pas vu cent fois la pousser du regard, de la tete et meme des epaules, comme si ces mouvements, purement symboliques, pouvaient rectifier son trajet? Des mouvements non moins significatifs se produisent quand la bille manque d’une impulsion suffisante. Et cliez les joueurs novices, ils sont quelquefois accuses au point d’eveiller le sourire sur les levres des spectateurs.” Such movements, as it appeirs to me, may be attributed simply to habit. As often as a man has wished to move an object to one side, he has always pushed it to that side when forwards, he has pushed it forwards; and if he has wished to arrest it, he has pulled backwards. Therefore, when a man sees his ball travelling in a wrong direction, and he intensely wishes it to go in another direction, he cannot avoid, from long habit, unconsciously performing movements which in other cases he has found effectual.

As an instance of sympathetic movements Gratiolet gives (p. 212) the following case:—”un jeune chien A oreilles droites, auquel son maitre presente de loin quelque viande appetissante, fixe avec ardeur ses yeux sur cet objet dont il suit tous les mouvements, et pendant que les yeux regardent, les deux oreilles se portent en avant comme si cet objet pouvait etre entendu.” Here, instead of speaking of sympathy between the ears and eyes, it appears to me more simple to believe, that as dogs during many generations have, whilst intently looking at any object, pricked their ears in order to perceive any sound; and conversely have looked intently in the direction of a sound to which they may have listened, the movements of these organs have become firmly associated together through long-continued habit.

Dr. Piderit published in 1859 an essay on Expression, which I have not seen, but in which, as he states, he forestalled Gratiolet in many of his views. In 1867 he published his ‘Wissenschaftliches System der Mimik und Physiognomik.’ It is hardly possible to give in a few sentences a fair notion of his views; perhaps the two following sentences will tell as much as can be briefly told: “the muscular movements of expression are in part related to imaginary objects, and in part to imaginary sensorial impressions. In this proposition lies the key to the comprehension of all expressive muscular movements.” (s. 25) Again, “Expressive movements manifest themselves chiefly in the numerous and mobile muscles of the face, partly because the nerves by which they are set into motion originate in the most immediate vicinity of the mind-organ, but partly also because these muscles serve to support the organs of sense.” (s. 26.) If Dr. Piderit had studied Sir C. Bell’s work, he would probably not have said (s. 101) that violent laughter causes a frown from partaking of the nature of pain; or that with infants (s. 103) the tears irritate the eyes, and thus excite the contraction of the surrounding in muscles. Many good remarks are scattered throughout this volume, to which I shall hereafter refer.

Short discussions on Expression may be found in various works, which need not here be particularised. Mr. Bain, however, in two of his works has treated the subject at some length. He says,[8] “I look upon the expression so-called as part and parcel of the feeling. I believe it to be a general law of the mind that along with the fact of inward feeling or consciousness, there is a diffusive action or excitement over the bodily members.” In another place he adds, “A very considerable number of the facts may be brought under the following principle: namely, that states of pleasure are connected with an increase, and states of pain with an abatement, of some, or all, of the vital functions.” But the above law of the diffusive action of feelings seems too general to throw much light on special expressions.

Mr. Herbert Spencer, in treating of the Feelings in his ‘Principles of Psychology’ (1855), makes the following remarks:—”Fear, when strong, expresses itself in cries, in efforts to hide or escape, in palpitations and tremblings; and these are just the manifestations that would accompany an actual experience of the evil feared. The destructive passions are shown in a general tension of the muscular system, in gnashing of the teeth and protrusion of the claws, in dilated eyes and nostrils in growls; and these are weaker forms of the actions that accompany the killing of prey.” Here we have, as I believe, the true theory of a large number of expressions; but the chief interest and difficulty of the subject lies in following out the wonderfully complex results. I infer that some one (but who he is I have not been able to ascertain) formerly advanced a nearly similar view, for Sir C. Bell says,[9] “It has been maintained that what are called the external signs of passion, are only the concomitants of those voluntary movements which the structure renders necessary.” Mr. Spencer has also published[10] a valuable essay on the physiology of Laughter, in which he insists on “the general law that feeling passing a certain pitch, habitually vents itself in bodily action,” and that “an overflow of nerve-force undirected by any motive, will manifestly take first the most habitual routes; and if these do not suffice, will next overflow into the less habitual ones.” This law I believe to be of the highest importance in throwing light on our subject.’[11]

All the authors who have written on Expression, with the exception of Mr. Spencer—the great expounder of the principle of Evolution—appear to have been firmly convinced that species, man of course included, came into existence in their present condition. Sir C. Bell, being thus convinced, maintains that many of our facial muscles are “purely instrumental in expression;” or are “a special provision” for this sole object.[12] But the simple fact that the anthropoid apes possess the same facial muscles as we do,[13] renders it very improbable that these muscles in our case serve exclusively for expression; for no one, I presume, would be inclined to admit that monkeys have been endowed with special muscles solely for exhibiting their hideous grimaces. Distinct uses, independently of expression, can indeed be assigned with much probability for almost all the facial muscles.

Sir C. Bell evidently wished to draw as broad a distinction as possible between man and the lower animals; and he consequently asserts that with “the lower creatures there is no expression but what may be referred, more or less plainly, to their acts of volition or necessary instincts.” He further maintains that their faces “seem chiefly capable of expressing rage and fear.”[14] But man himself cannot express love and humility by external signs, so plainly as does a dog, when with drooping ears, hanging lips, flexuous body, and wagging tail, he meets his beloved master. Nor can these movements in the dog be explained by acts of volition or necessary instincts, any more than the beaming eyes and smiling cheeks of a man when he meets an old friend. If Sir C. Bell had been questioned about the expression of affection in the dog, he would no doubt have answered that this animal had been created with special instincts, adapting him for association with man, and that all further enquiry on the subject was superfluous.

Although Gratiolet emphatically denies[15] that any muscle has been developed solely for the sake of expression, he seems never to have reflected on the principle of evolution. He apparently looks at each species as a separate creation. So it is with the other writers on Expression. For instance, Dr. Duchenne, after speaking of the movements of the limbs, refers to those which give expression to the face, and remarks:[16] “Le createur n’a donc pas eu a se preoccuper ici des besoins de la mecanique; il a pu, selon sa sagesse, ou—que l’on me pardonne cette maniere de parler—par une divine fantaisie, mettre en action tel ou tel muscle, un seul ou plusieurs muscles a la fois, lorsqu’il a voulu que les signes caracteristiques des passions, meme les plus fugaces, lussent ecrits passagerement sur la face de l’homme. Ce langage de la physionomie une fois cree, il lui a suffi, pour le rendre universel et immuable, de donner a tout etre humain la faculte instinctive d’exprimer toujours ses sendments par la contraction des memes muscles.”

Many writers consider the whole subject of Expression as inexplicable. Thus the illustrious physiologist Muller, says,[17] “The completely different expression of the features in different passions shows that, according to the kind of feeling excited, entirely different groups of the fibres of the facial nerve are acted on. Of the cause of this we are quite ignorant.”

No doubt as long as man and all other animals are viewed as independent creations, an effectual stop is put to our natural desire to investigate as far as possible the causes of Expression. By this doctrine, anything and everything can be equally well explained; and it has proved as pernicious with respect to Expression as to every other branch of natural history. With mankind some expressions, such as the bristling of the hair under the influence of extreme terror, or the uncovering of the teeth under that of furious rage, can hardly be understood, except on the belief that man once existed in a much lower and animal-like condition. The community of certain expressions in distinct though allied species, as in the movements of the same facial muscles during laughter by man and by various monkeys, is rendered somewhat more intelligible, if we believe in their descent from a common progenitor. He who admits on general grounds that the structure and habits of all animals have been gradually evolved, will look at the whole subject of Expression in a new and interesting light.

The study of Expression is difficult, owing to the movements being often extremely slight, and of a fleeting nature. A difference may be clearly perceived, and yet it may be impossible, at least I have found it so, to state in what the difference consists. When we witness any deep emotion, our sympathy is so strongly excited, that close observation is forgotten or rendered almost impossible; of which fact I have had many curious proofs. Our imagination is another and still more serious source of error; for if from the nature of the circumstances we expect to see any expression, we readily imagine its presence. Notwithstanding Dr. Duchenne’s great experience, he for a long time fancied, as he states, that several muscles contracted under certain emotions, whereas he ultimately convinced himself that the movement was confined to a single muscle.

In order to acquire as good a foundation as possible, and to ascertain, independently of common opinion, how far particular movements of the features and gestures are really expressive of certain states of the mind, I have found the following means the most serviceable. In the first place, to observe infants; for they exhibit many emotions, as Sir C. Bell remarks, “with extraordinary force;” whereas, in after life, some of our expressions “cease to have the pure and simple source from which they spring in infancy.”[18]

In the second place, it occurred to me that the insane ought to be studied, as they are liable to the strongest passions, and give uncontrolled vent to them. I had, myself, no opportunity of doing this, so I applied to Dr. Maudsley and received from him an introduction to Dr. J. Crichton Browne, who has charge of an immense asylum near Wakefield, and who, as I found, had already attended to the subject. This excellent observer has with unwearied kindness sent me copious notes and descriptions, with valuable suggestions on many points; and I can hardly over-estimate the value of his assistance. I owe also, to the kindness of Mr. Patrick Nicol, of the Sussex Lunatic Asylum, interesting statements on two or three points.

Thirdly Dr. Duchenne galvanized, as we have already seen, certain muscles in the face of an old man, whose skin was little sensitive, and thus produced various expressions which were photographed on a large scale. It fortunately occurred to me to show several of the best plates, without a word of explanation, to above twenty educated persons of various ages and both sexes, asking them, in each case, by what emotion or feeling the old man was supposed to be agitated; and I recorded their answers in the words which they used. Several of the expressions were instantly recognised by almost everyone, though described in not exactly the same terms; and these may, I think, be relied on as truthful, and will hereafter be specified. On the other hand, the most widely different judgments were pronounced in regard to some of them. This exhibition was of use in another way, by convincing me how easily we may be misguided by our imagination; for when I first looked through Dr. Duchenne’s photographs, reading at the same time the text, and thus learning what was intended, I was struck with admiration at the truthfulness of all, with only a few exceptions. Nevertheless, if I had examined them without any explanation, no doubt I should have been as much perplexed, in some cases, as other persons have been.

Fourthly, I had hoped to derive much aid from the great masters in painting and sculpture, who are such close observers. Accordingly, I have looked at photographs and engravings of many well-known works; but, with a few exceptions, have not thus profited. The reason no doubt is, that in works of art, beauty is the chief object; and strongly contracted facial muscles destroy beauty.[19] The story of the composition is generally told with wonderful force and truth by skilfully given accessories.

Fifthly, it seemed to me highly important to ascertain whether the same expressions and gestures prevail, as has often been asserted without much evidence, with all the races of mankind, especially with those who have associated but little with Europeans. Whenever the same movements of the features or body express the same emotions in several distinct races of man, we may infer with much probability, that such expressions are true ones,—that is, are innate or instinctive. Conventional expressions or gestures, acquired by the individual during early life, would probably have differed in the different races, in the same manner as do their languages. Accordingly I circulated, early in the year 1867, the following printed queries with a request, which has been fully responded to, that actual observations, and not memory, might be trusted. These queries were written after a considerable interval of time, during which my attention had been otherwise directed, and I can now see that they might have been greatly improved. To some of the later copies, I appended, in manuscript, a few additional remarks:—

(1.) Is astonishment expressed by the eyes and mouth being opened wide, and by the eyebrows being raised?

(2.) Does shame excite a blush when the colour of the skin allows it to be visible? and especially how low down the body does the blush extend?

(3.) When a man is indignant or defiant does he frown, hold his body and head erect, square his shoulders and clench his fists?

(4) When considering deeply on any subject, or trying to understand any puzzle, does he frown, or wrinkle the skin beneath the lower eyelids?

(5.) When in low spirits, are the corners of the mouth depressed, and the inner corner of the eyebrows raised by that muscle which the French call the “Grief muscle”? The eyebrow in this state becomes slightly oblique, with a little swelling at the Inner end; and the forehead is transversely wrinkled in the middle part, but not across the whole breadth, as when the eyebrows are raised in surprise. (6.) When in good spirits do the eyes sparkle, with the skin a little wrinkled round and under them, and with the mouth a little drawn back at the corners?

(7.) When a man sneers or snarls at another, is the corner of the upper lip over the canine or eye tooth raised on the side facing the man whom he addresses?

(8) Can a dogged or obstinate expression be recognized, which is chiefly shown by the mouth being firmly closed, a lowering brow and a slight frown?

(9.) Is contempt expressed by a slight protrusion of the lips and by turning up the nose, and with a slight expiration?

(10) Is disgust shown by the lower lip being turned down, the upper lip slightly raised, with a sudden expiration, something like incipient vomiting, or like something spit out of the mouth?

(11.) Is extreme fear expressed in the same general manner as with Europeans?

(12.) Is laughter ever carried to such an extreme as to bring tears into the eyes?

(13.) When a man wishes to show that he cannot prevent something being done, or cannot himself do something, does he shrug his shoulders, turn inwards his elbows, extend outwards his hands and open the palms; with the eyebrows raised?

(14) Do the children when sulky, pout or greatly protrude the lips?

(15.) Can guilty, or sly, or jealous expressions be recognized? though I know not how these can be defined.

(16.) Is the head nodded vertically in affirmation, and shaken laterally in negation?

Observations on natives who have had little communication with Europeans would be of course the most valuable, though those made on any natives would be of much interest to me. General remarks on expression are of comparatively little value; and memory is so deceptive that I earnestly beg it may not be trusted. A definite description of the countenance under any emotion or frame of mind, with a statement of the circumstances under which it occurred, would possess much value.

To these queries I have received thirty-six answers from different observers, several of them missionaries or protectors of the aborigines, to all of whom I am deeply indebted for the great trouble which they have taken, and for the valuable aid thus received. I will specify their names, &c., towards the close of this chapter, so as not to interrupt my present remarks. The answers relate to several of the most distinct and savage races of man. In many instances, the circumstances have been recorded under which each expression was observed, and the expression itself described. In such cases, much confidence may be placed in the answers. When the answers have been simply yes or no, I have always received them with caution. It follows, from the information thus acquired, that the same state of mind is expressed throughout the world with remarkable uniformity; and this fact is in itself interesting as evidence of the close similarity in bodily structure and mental disposition of all the races, of mankind.

Sixthly, and lastly, I have attended as closely as I could, to the expression of the several passions in some of the commoner animals; and this I believe to be of paramount importance, not of course for deciding how far in man certain expressions are characteristic of certain states of mind, but as affording the safest basis for generalisation on the causes, or origin, of the various movements of Expression. In observing animals, we are not so likely to be biassed by our imagination; and we may feel safe that their expressions are not conventional.

From the reasons above assigned, namely, the fleeting nature of some expressions (the changes in the features being often extremely slight); our sympathy being easily aroused when we behold any strong emotion, and our attention thus distracted; our imagination deceiving us, from knowing in a vague manner what to expect, though certainly few of us know what the exact changes in the countenance are; and lastly, even our long familiarity with the subject,—from all these causes combined, the observation of Expression is by no means easy, as many persons, whom I have asked to observe certain points, have soon discovered. Hence it is difficult to determine, with certainty, what are the movements of the features and of the body, which commonly characterize certain states of the mind. Nevertheless, some of the doubts and difficulties have, as I hope, been cleared away by the observation of infants,—of the insane,—of the different races of man,—of works of art,—and lastly, of the facial muscles under the action of galvanism, as effected by Dr. Duchenne.

But there remains the much greater difficulty of understanding the cause or origin of the several expressions, and of judging whether any theoretical explanation is trustworthy. Besides, judging as well as we can by our reason, without the aid of any rules, which of two or more explanations is the most satisfactory, or are quite unsatisfactory, I see only one way of testing our conclusions. This is to observe whether the same principle by which one expression can, as it appears, be explained, is applicable in other allied cases; and especially, whether the same general principles can be applied with satisfactory results, both to man and the lower animals. This latter method, I am inclined to think, is the most serviceable of all. The difficulty of judging of the truth of any theoretical explanation, and of testing it by some distinct line of investigation, is the great drawback to that interest which the study seems well fitted to excite.

Finally, with respect to my own observations, I may state that they were commenced in the year 1838; and from that time to the present day, I have occasionally attended to the subject. At the above date, I was already inclined to believe in the principle of evolution, or of the derivation of species from other and lower forms. Consequently, when I read Sir C. Bell’s great work, his view, that man had been created with certain muscles specially adapted for the expression of his feelings, struck me as unsatisfactory. It seemed probable that the habit of expressing our feelings by certain movements, though now rendered innate, had been in some manner gradually acquired. But to discover how such habits had been acquired was perplexing in no small degree. The whole subject had to be viewed under a new aspect, and each expression demanded a rational explanation. This belief led me to attempt the present work, however imperfectly it may have been executed.————

I will now give the names of the gentlemen to whom, as I have said, I am deeply indebted for information in regard to the expressions exhibited by various races of man, and I will specify some of the circumstances under which the observations were in each case made. Owing to the great kindness and powerful influence of Mr. Wilson, of Hayes Place, Kent, I have received from Australia no less than thirteen sets of answers to my queries. This has been particularly fortunate, as the Australian aborigines rank amongst the most distinct of all the races of man. It will be seen that the observations have been chiefly made in the south, in the outlying parts of the colony of Victoria; but some excellent answers have been received from the north.

Mr. Dyson Lacy has given me in detail some valuable observations, made several hundred miles in the interior of Queensland. To Mr. R. Brough Smyth, of Melbourne, I am much indebted for observations made by himself, and for sending me several of the following letters, namely:—From the Rev. Mr. Hagenauer, of Lake Wellington, a missionary in Gippsland, Victoria, who has had much experience with the natives. From Mr. Samuel Wilson, a landowner, residing at Langerenong, Wimmera, Victoria. From the Rev. George Taplin, superintendent of the native Industrial Settlement at Port Macleay. From Mr. Archibald G. Lang, of Coranderik, Victoria, a teacher at a school where aborigines, old and young, are collected from all parts of the colony. From Mr. H. B. Lane, of Belfast, Victoria, a police magistrate and warden, whose observations, as I am assured, are highly trustworthy. From Mr. Templeton Bunnett, of Echuca, whose station is on the borders of the colony of Victoria, and who has thus been able to observe many aborigines who have had little intercourse with white men. He compared his observations with those made by two other gentlemen long resident in the neighbourhood. Also from Mr. J. Bulmer, a missionary in a remote part of Gippsland, Victoria.

I am also indebted to the distinguished botanist, Dr. Ferdinand Muller, of Victoria, for some observations made by himself, and for sending me others made by Mrs. Green, as well as for some of the foregoing letters.

In regard to the Maoris of New Zealand, the Rev. J. W. Stack has answered only a few of my queries; but the answers have been remarkably full, clear, and distinct, with the circumstances recorded under which the observations were made.

The Rajah Brooke has given me some information with respect to the Dyaks of Borneo.

Respecting the Malays, I have been highly successful; for Mr. F. Geach (to whom I was introduced by Mr. Wallace), during his residence as a mining engineer in the interior of Malacca, observed many natives, who had never before associated with white men. He wrote me two long letters with admirable and detailed observations on their expression. He likewise observed the Chinese immigrants in the Malay archipelago.

The well-known naturalist, H. M. Consul, Mr. Swinhoe, also observed for me the Chinese in their native country; and he made inquiries from others whom he could trust.

In India Mr. H. Erskine, whilst residing in his official capacity in the Admednugur District in the Bombay Presidency, attended to the expression of the inhabitants, but found much difficulty in arriving at any safe conclusions, owing to their habitual concealment of all emotions in the presence of Europeans. He also obtained information for me from Mr. West, the Judge in Canara, and he consulted some intelligent native gentlemen on certain points. In Calcutta Mr. J. Scott, curator of the Botanic Gardens, carefully observed the various tribes of men therein employed during a considerable period, and no one has sent me such full and valuable details. The habit of accurate observation, gained by his botanical studies, has been brought to bear on our present subject. For Ceylon I am much indebted to the Rev. S. O. Glenie for answers to some of my queries.

Turning to Africa, I have been unfortunate with respect to the negroes, though Mr. Winwood Reade aided me as far as lay in his power. It would have been comparatively easy to have obtained information in regard to the negro slaves in America; but as they have long associated with white men, such observations would have possessed little value. In the southern parts of the continent Mrs. Barber observed the Kafirs and Fingoes, and sent me many distinct answers. Mr. J. P. Mansel Weale also made some observations on the natives, and procured for me a curious document, namely, the opinion, written in English, of Christian Gaika, brother of the Chief Sandilli, on the expressions of his fellow-countrymen. In the northern regions of Africa Captain Speedy, who long resided with the Abyssinians, answered my queries partly from memory and partly from observations made on the son of King Theodore, who was then under his charge. Professor and Mrs. Asa Gray attended to some points in the expressions of the natives, as observed by them whilst ascending the Nile.

On the great American continent Mr. Bridges, a catechist residing with the Fuegians, answered some few questions about their expression, addressed to him many years ago. In the northern half of the continent Dr. Rothrock attended to the expressions of the wild Atnah and Espyox tribes on the Nasse River, in North-Western America. Mr. Washington Matthews Assistant-Surgeon in the United States Army, also observed with special care (after having seen my queries, as printed in the ‘Smithsonian Report’) some of the wildest tribes in the Western parts of the United States, namely, the Tetons, Grosventres, Mandans, and Assinaboines; and his answers have proved of the highest value.

Lastly, besides these special sources of information, I have collected some few facts incidentally given in books of travels.——

Muscles of the Human Face. Fig 1-2

Muscles of the Human Face. Fig 3

As I shall often have to refer, more especially in the latter part of this volume, to the muscles of the human face, I have had a diagram (fig. 1) copied and reduced from Sir C. Bell’s work, and two others, with more accurate details (figs. 2 and 3), from Herde’s well-known ‘Handbuch der Systematischen Anatomie des Menschen.’ The same letters refer to the same muscles in all three figures, but the names are given of only the more important ones to which I shall have to allude. The facial muscles blend much together, and, as I am informed, hardly appear on a dissected face so distinct as they are here represented. Some writers consider that these muscles consist of nineteen pairs, with one unpaired;[20] but others make the number much larger, amounting even to fifty-five, according to Moreau. They are, as is admitted by everyone who has written on the subject, very variable in structure; and Moreau remarks that they are hardly alike in half-a-dozen subjects.[21] They are also variable in function. Thus the power of uncovering the canine tooth on one side differs much in different persons. The power of raising the wings of the nostrils is also, according to Dr. Piderit,[22] variable in a remarkable degree; and other such cases could be given.

Finally, I must have the pleasure of expressing my obligations to Mr. Rejlander for the trouble which he has taken in photographing for me various expressions and gestures. I am also indebted to Herr Kindermann, of Hamburg, for the loan of some excellent negatives of crying infants; and to Dr. Wallich for a charming one of a smiling girl. I have already expressed my obligations to Dr. Duchenne for generously permitting me to have some of his large photographs copied and reduced. All these photographs have been printed by the Heliotype process, and the accuracy of the copy is thus guaranteed. These plates are referred to by Roman numerals.

I am also greatly indebted to Mr. T. W. Wood for the extreme pains which he has taken in drawing from life the expressions of various animals. A distinguished artist, Mr. Riviere, has had the kindness to give me two drawings of dogs—one in a hostile and the other in a humble and caressing frame of mind. Mr. A. May has also given me two similar sketches of dogs. Mr. Cooper has taken much care in cutting the blocks. Some of the photographs and drawings, namely, those by Mr. May, and those by Mr. Wolf of the Cynopithecus, were first reproduced by Mr. Cooper on wood by means of photography, and then engraved: by this means almost complete fidelity is ensured.