Hick’s law

The Paradox of Choice – Why More Is Less is a 2004 book by American psychologist Barry Schwartz. In the book, Schwartz argues that eliminating consumer choices can greatly reduce anxiety for shoppers. Autonomy and Freedom of choice are critical to our well being, and choice is critical to freedom and autonomy. Nonetheless, though modern […]

The Paradox of Choice – Why More Is Less is a 2004 book by American psychologist Barry Schwartz. In the book, Schwartz argues that eliminating consumer choices can greatly reduce anxiety for shoppers.

Autonomy and Freedom of choice are critical to our well being, and choice is critical to freedom and autonomy. Nonetheless, though modern Americans have more choice than any group of people ever has before, and thus, presumably, more freedom and autonomy, we don’t seem to be benefiting from it psychologically.

—?quoted from Ch.5, The Paradox of Choice, 2004

Hick’s law, or the Hick–Hyman Law, named after British and American psychologists William Edmund Hick and Ray Hyman, describes the time it takes for a person to make a decision as a result of the possible choices he or she has: increasing the number of choices will increase the decision time logarithmically. The Hick–Hyman law assesses cognitive information capacity in choice reaction experiments. The amount of time taken to process a certain amount of bits in the Hick–Hyman law is known as the rate of gain of information.

Hick’s law is sometimes cited to justify menu design decisions. For example, to find a given word (e.g. the name of a command) in a randomly ordered word list (e.g. a menu), scanning of each word in the list is required, consuming linear time, so Hick’s law does not apply. However, if the list is alphabetical and the user knows the name of the command, he or she may be able to use a subdividing strategy that works in logarithmic time.[1]

Studies suggest that the search for a word within a randomly ordered list – in which the reaction time increases linearly according to the number of items – does not allow for the generalization of the scientific law, considering that, in other conditions, the reaction time may not be linearly associated to the logarithm of the number of elements or even show other variations of the basic plane.

Exceptions to Hick’s law have been identified in studies of verbal response to familiar stimuli, where there is no relationship or only a subtle increase in the reaction time associated with an increased number of elements,[4] and saccade responses, where it was shown that there is either no relationship,[5] or a decrease in the saccadic time with the increase of the number of elements, thus an antagonistic effect to that postulated by Hick’s law.[6]

The generalization of Hick’s law was also tested in studies on the predictability of transitions associated with the reaction time of elements that appeared in a structured sequence.[7] [8] This process was first described as being in accordance to Hick’s law,[9] but more recently it was shown that the relationship between predictability and reaction time is sigmoid, not linear associated with different modes of action. [10]

The power law of practice states that the logarithm of the reaction time for a particular task decreases linearly with the logarithm of the number of practice trials taken. It is an example of the learning curve effect on performance. It was first proposed as a psychological law by Newell & Rosenblom.[1] Delaney et al. showed that the power law fit better than an exponential if the analysis was performed across strategies, for a mental arithmetic task.[2]

However, subsequent research by Heathcote, Brown, and Mewhort suggests that the power function observed in learning curves that are averaged across participants is an artifact of aggregation.[3] Heathcote et al. suggest that individual-level data is better fit by an exponential function and the authors demonstrate that the multiple exponential curves will average to produce a curve that is misleadingly well fit by a power function.

The power function is based on the idea that something is slowing down the learning process; at least, this is what the function suggests. Our learning does not occur at a constant rate according this function; our learning is hindered. The exponential function shows that learning increases at a constant rate in relationship to what is left to be learned. If you know absolutely nothing about a topic, you can learn 50% of the information quickly, but when you have 50% less to learn, it takes more time to learn that final 50%.

Research by Logan suggests that the instance theory of automaticity can be used to explain why the power law is deemed an accurate portrayal of reaction time learning curves.[4] A skill is automatic when there is one step from stimulus to retrieval. For many problem solving tasks, reaction time is related to how long it takes to discover an answer, but as time goes on, certain answers are stored within the individual’s memory and they have to simply recall the information, thus reducing reaction time. This is the first theory that addresses the why of the power law of practice.

Power function:

RT = aP?b + c

Exponential function:

RT = ae?b(P-1) + c


RT = Trial Completion Time
P = Trial Number, starting from 1 (for exponential functions the P-1 argument is used)
a, b, and c, are constants

Practice effects are also influenced by latency. Anderson, Fincham, and Douglass looked at the relationship between practice and latency and people’s ability to retain what they learned. As the time between trials increases, there is greater decay. The latency function relates to the forgetting curve.[5]

Latency Function:

latency = A + B*Td


A = asymptotic latency B = latency that varies T = time between introduction and testing d = decay rate

Integrative body-mind training (IBMT)

Front Psychol. 2015; 6: 212. Published online 2015 Feb 26. doi:  10.3389/fpsyg.2015.00212 PMCID: PMC4341506 Short-term meditation increases blood flow in anterior cingulate cortex and insula Yi-Yuan Tang,1,2,* Qilin Lu,3 Hongbo Feng,3,4 Rongxiang Tang,5 and Michael I. Posner2 Author information ► Article notes ► Copyright and License information ► This article has been cited by other […]


Asymmetry in frontal electrical activity has been reported to be associated with positive mood. One form of mindfulness meditation, integrative body-mind training (IBMT) improves positive mood and neuroplasticity. The purpose of this study is to determine whether short-term IBMT improves mood and induces frontal asymmetry. This study showed that 5-days (30-min per day) IBMT significantly enhanced cerebral blood flow (CBF) in subgenual/adjacent ventral anterior cingulate cortex (ACC), medial prefrontal cortex and insula. The results showed that both IBMT and relaxation training increased left laterality of CBF, but only IBMT improved CBF in left ACC and insula, critical brain areas in self-regulation.

Keywords: integrative body–mind training, cerebral blood flow, positive mood, frontal asymmetry, anterior cingulate cortex

Short term “integrative body-mind training” (IBMT) improves self- and autonomic regulation

A group from Univ. of Oregon in collaboration with the Institute of Neuroinformatics and Laboratory for Body and Mind, Dalian University of Technology, Dalian, China has found more evidence (see 2007, 2009 and 2010 articles) that short-term meditation in the form of IBMT can improve self-regulation and components of attention.

What is IBMT? According to the authors, it was developed in the 1990s as a technique adopted from traditional Chinese medicine and incorporates aspects of meditation and mindfulness training. “IBMT achieves the desired state by first giving a brief instructional period on the method (we call it initial mind setting and its goal is to induce a cognitive or emotional set that will influence the training). The method stresses no effort to control thoughts, but instead a state of restful alertness that allows a high degree of awareness of body, breathing, and external instructions from a compact disc. It stresses a balanced state of relaxation while focusing attention. Thought control is achieved gradually through posture and relaxation, body–mind harmony, and balance with the help of the coach rather than by making the trainee attempt an internal struggle to control thoughts in accordance with instruction. Training is typically presented in a standardized way by compact disc and guided by a skillful IBMT coach”.


In positive psychology, flow, also known as the zone, is the mental state of operation in which a person performing an activity is fully immersed in a feeling of energized focus, full involvement, and enjoyment in the process of the activity. In essence, flow is characterized by complete absorption in what one does. Named by […]

In positive psychology, flow, also known as the zone, is the mental state of operation in which a person performing an activity is fully immersed in a feeling of energized focus, full involvement, and enjoyment in the process of the activity. In essence, flow is characterized by complete absorption in what one does. Named by Mihály Csíkszentmihályi, the concept has been widely referenced across a variety of fields (and has an especially big recognition in occupational therapy), though has existed for thousands of years under other guises, notably in some Eastern religions.[1] Achieving flow is often colloquially referred to as being in the zone.

According to Csikszentmihályi, flow is completely focused motivation. It is a single-minded immersion and represents perhaps the ultimate experience in harnessing the emotions in the service of performing and learning. In flow, the emotions are not just contained and channeled, but positive, energized, and aligned with the task at hand. The hallmark of flow is a feeling of spontaneous joy, even rapture, while performing a task,[2] although flow is also described (below) as a deep focus on nothing but the activity – not even oneself or one’s emotions.

Flow has many of the same characteristics as (the positive aspects of) hyperfocus. However, hyperfocus is not always described in a positive light. Some examples include spending “too much” time playing video games or getting side-tracked and pleasurably absorbed by one aspect of an assignment or task to the detriment of the overall assignment. In some cases, hyperfocus can “capture” a person, perhaps causing them to appear unfocused or to start several projects, but complete few.

Jeanne Nakamura and Csíkszentmihályi identify the following six factors as encompassing an experience of flow.[3]

  1. Intense and focused concentration on the present moment
  2. Merging of action and awareness
  3. A loss of reflective self-consciousness
  4. A sense of personal control or agency over the situation or activity
  5. A distortion of temporal experience, one’s subjective experience of time is altered
  6. Experience of the activity as intrinsically rewarding, also referred to as autotelic experience

Those aspects can appear independently of each other, but only in combination do they constitute a so-called flow experience. Additionally, psychology expert, Kendra Cherry, has mentioned three other components that Csíkszentmihályi lists as being a part of the flow experience:[4]

  1. “Immediate feedback” [4]
  2. Feeling that you have the potential to succeed
  3. Feeling so engrossed in the experience, that other needs become negligible

Just as with the conditions listed above, these conditions can be independent of one another.

A flow state can be entered while performing any activity, although it is most likely to occur when one is wholeheartedly performing a task or activity for intrinsic purposes.[7][11] Passive activities like taking a bath or even watching TV usually do not elicit flow experiences as individuals have to actively do something to enter a flow state.[12][13] While the activities that induce flow may vary and be multifaceted, Csikszentmihályi asserts that the experience of flow is similar despite the activity.[14]

Flow theory postulates three conditions that have to be met to achieve a flow state:

  1. One must be involved in an activity with a clear set of goals and progress. This adds direction and structure to the task.[15]
  2. The task at hand must have clear and immediate feedback. This helps the person negotiate any changing demands and allows them to adjust their performance to maintain the flow state.[15]
  3. One must have a good balance between the perceived challenges of the task at hand and their own perceived skills. One must have confidence in one’s ability to complete the task at hand.[15]

However, it was argued that the antecedent factors of flow are interrelated, as a perceived balance between challenges and skills requires that one knows what he or she has to do (clear goals) and how successful he or she is in doing it (immediate feedback). Thus, a perceived fit of skills and task demands can be identified as the central precondition of flow experiences.[16]

In 1987, Massimini, Csíkszentmihályi and Carli published the 8-channel model of flow shown here.[17] Antonella Delle Fave, who worked with Fausto Massimini at the University of Milan, now calls this graph the Experience Fluctuation Model.[18] The Experience Fluctuation Model depicts the channels of experience that result from different levels of perceived challenges and perceived skills. This graph illustrates one further aspect of flow: it is more likely to occur when the activity at hand is a higher-than-average challenge (above the center point) and the individual has above-average skills (to the right of the center point).[7] The center of this graph (where the sectors meet) represents one’s average levels of challenge and skill across all activities an individual performs during their daily life. The further from the center an experience is, the greater the intensity of that state of being (whether it is flow or anxiety or boredom or relaxation).[11]

Several problems of this model have been discussed in literature.[16][19] One is, that it does not ensure a perceived balance between challenges and skills which is supposed to be the central precondition of flow experiences. Individuals with a low average level of skills and a high average level of challenges (or the other way round) do not necessarily experience a fit between skills and challenges when both are above their individual average.[20] In addition, one study found that low challenge situations which were surpassed by skill were associated with enjoyment, relaxation, and happiness, which, they claim, is contrary to flow theory.[21]

Schaffer (2013) proposed 7 flow conditions:

  1. Knowing what to do
  2. Knowing how to do it
  3. Knowing how well you are doing
  4. Knowing where to go (if navigation is involved)
  5. High perceived challenges
  6. High perceived skills
  7. Freedom from distractions[22]

Schaffer also published a measure, the Flow Condition Questionnaire (FCQ), to measure each of these 7 flow conditions for any given task or activity.[22]


the future

What the Marshmallow Test Really Teaches About Self-Control JACOBA URIST SEP 24, 2014 One of the most influential modern psychologists, Walter Mischel, addresses misconceptions about his study, and discusses how both adults and kids can master willpower. Published on Dec 14, 2012 Silvia Helena Barcellos is an Associate Economist at RAND Corporation, Santa Monica Office. […]

What the Marshmallow Test Really Teaches About Self-Control

One of the most influential modern psychologists, Walter Mischel, addresses misconceptions about his study, and discusses how both adults and kids can master willpower.

Published on Dec 14, 2012
Silvia Helena Barcellos is an Associate Economist at RAND Corporation, Santa Monica Office. Her research focuses on applied microeconomics topics in labor and development economics. Her labor economics research includes works on the economic causes and consequences of immigration to the United States and on the effects of taxation on location and organizational choices of firms and individuals. In research on development economics, Barcellos has investigated the existence of gender discrimination in parental time investments in India.

The Stanford marshmallow experiment[1] was a series of studies on delayed gratification in the late 1960s and early 1970s led by psychologist Walter Mischel, then a professor at Stanford University. In these studies, a child was offered a choice between one small reward provided immediately or two small rewards (i.e., a larger later reward) if they waited for a short period, approximately 15 minutes, during which the tester left the room and then returned. (The reward was sometimes a marshmallow, but often a cookie or apretzel.) In follow-up studies, the researchers found that children who were able to wait longer for the preferred rewards tended to have better life outcomes, as measured by SAT scores,[2] educational attainment,[3] body mass index (BMI),[4] and other life measures.[5]

The experiment has its roots in an earlier one performed in Trinidad, where Mischel noticed that the different ethnic groups living on the island had contrasting stereotypes about one another, specifically the other’s perceived recklessness, self-control, and ability to have fun.[6] This small (n= 53) study focused on male and female children aged 7 to 9 (35Black and 18 East Indian) in a rural Trinidad school. The children were required to indicate a choice between receiving a 1¢ candy immediately, or having a (preferable) 10¢ candy given to them in one week’s time. Mischel reported a significant ethnic difference, with Indian children showing far more ability to delay gratification as compared to African students, as well as large age differences, and that “Comparison of the ‘high’ versus ‘low’ socioeconomic groups on the experimental choice did not yield a significant difference”.[6] Absence of the father was prevalent in the African-descent group (occurring only once in the East Indian group), and this variable showed the strongest link to delay of gratification, with children from intact families showing superior ability to delay.

Dunbar’s number

Dunbar’s number is a suggested cognitive limit to the number of people with whom one can maintain stable social relationships. These are relationships in which an individualknows who each person is and how each person relates to every other person.[1][2][3][4][5][6] This number was first proposed in the 1990s by British anthropologist Robin Dunbar, who found […]

Dunbar’s number is a suggested cognitive limit to the number of people with whom one can maintain stable social relationships. These are relationships in which an individualknows who each person is and how each person relates to every other person.[1][2][3][4][5][6] This number was first proposed in the 1990s by British anthropologist Robin Dunbar, who found a correlation between primate brain size and average social group size.[7] By using the average human brain size and extrapolating from the results of primates, he proposed that humans can only comfortably maintain 150 stable relationships.[8] Proponents assert that numbers larger than this generally require more restrictive rules, laws, and enforced norms to maintain a stable, cohesive group. It has been proposed to lie between 100 and 250, with a commonly used value of 150.[9][10] Dunbar’s number states the number of people one knows and keeps social contact with, and it does not include the number of people known personally with a ceased social relationship, nor people just generally known with a lack of persistent social relationship, a number which might be much higher and likely depends on long-term memory size.

Dunbar theorized that “this limit is a direct function of relative neocortex size, and that this in turn limits group size … the limit imposed by neocortical processing capacity is simply on the number of individuals with whom a stable inter-personal relationship can be maintained.” On the periphery, the number also includes past colleagues, such as high schoolfriends, with whom a person would want to reacquaint himself if they met again.[11]

Dunbar has argued that 150 would be the mean group size only for communities with a very high incentive to remain together. For a group of this size to remain cohesive, Dunbar speculated that as much as 42% of the group’s time would have to be devoted to social grooming. Correspondingly, only groups under intense survival pressure.

Dunbar, in Grooming, Gossip, and the Evolution of Language, proposes furthermore that language may have arisen as a “cheap” means of social grooming, allowing early humans to maintain social cohesion efficiently. Without language, Dunbar speculates, humans would have to expend nearly half their time on social grooming, which would have made productive, cooperative effort nearly impossible. Language may have allowed societies to remain cohesive, while reducing the need for physical and social intimacy.[12]

Dunbar’s number has since become of interest in anthropology, evolutionary psychology,[13] statistics, and business management. For example, developers of social software are interested in it, as they need to know the size of social networks their software needs to take into account; and in the modern military, operational psychologists seek such data to support or refute policies related to maintaining or improving unit cohesion and morale. A recent study has suggested that Dunbar’s number is applicable to online social networks[14][15] and communication networks (mobile phone).[16]

Philip Lieberman argues that since band societies of approximately 30-50 people are bounded by nutritional limitations to what group sizes can be fed without at least rudimentary agriculture, big human brains consuming more nutrients than ape brains, group sizes of approximately 150 cannot have been selected for in paleolithic humans.[20]Brains much smaller than human or even mammalian brains are also known to be able to support social relationships, including social insects with hierachies where each individual knows its place (such as the paper wasp with its societies of approximately 80 individuals [21]) and computer-simulated virtual autonomous agents with simple reaction programming emulating what is referred to in primatology as “ape politics”.[22]


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.

trait theory

In psychology, trait theory (also called dispositional theory) is an approach to the study of human personality. Trait theorists are primarily interested in the measurement of traits, which can be defined as habitual patterns of behavior, thought, and emotion.[1]According to this perspective, traits are relatively stable over time, differ across individuals (e.g. some people are […]

In psychology, trait theory (also called dispositional theory) is an approach to the study of human personality. Trait theorists are primarily interested in the measurement of traits, which can be defined as habitual patterns of behavior, thought, and emotion.[1]According to this perspective, traits are relatively stable over time, differ across individuals (e.g. some people are outgoing whereas others are shy), and influence behavior. Traits are in contrast to states which are more transitory dispositions.

In some theories and systems, traits are something a person either has or does not have, but in many others traits are dimensions such as extraversion vs. introversion, with each person rating somewhere along this spectrum.

Gordon Allport was an early pioneer in the study of traits, which he also referred to as dispositions. In his approach, “cardinal” traits are those that dominate and shape a person’s behavior; their ruling passions/obsessions, such as a need for money, fame etc. By contrast, “central” traits such as honesty are characteristics found in some degree in every person – and finally “secondary” traits are those seen only in certain circumstances (such as particular likes or dislikes that a very close friend may know), which are included to provide a complete picture of human complexity.

A wide variety of alternative theories and scales were later developed, including:

Currently, two general approaches are the most popular:

Neuroticism is a fundamental personality trait in the study of psychology characterized by anxiety, fear, moodiness, worry, envy, frustration, jealousy, and loneliness.[1] Individuals who score high on neuroticism are more likely than the average to experience such feelings as anxiety, anger, envy, guilt, and depressed mood.[2] They respond more poorly tostressors, are more likely to interpret ordinary situations as threatening, and minor frustrations as hopelessly difficult. They are often self-conscious and shy, and they may have trouble controlling urges and delaying gratification. Neuroticism is a prospective risk factor for most “common mental disorders“,[3] such as depression, phobia, panic disorder, other anxiety disorders, and substance use disorder—symptoms that traditionally have been called neuroses.[3][4][5][6][7]

Neuroticism appears to be related to physiological differences in the brain. Hans Eysenck theorized that neuroticism is a function of activity in the limbic system, and his research suggests that people who score highly on measures of neuroticism have a more reactive sympathetic nervous system, and are more sensitive to environmental stimulation.[20]

Behavioral genetics researchers have found that a significant portion of the variability on measures of neuroticism can be attributed to genetic factors.[21]

A study with positron emission tomography has found that healthy subjects that score high on the NEO PI-R neuroticism dimension tend to have high altanserin binding in the frontolimbic region of the brain—an indication that these subjects tend to have more of the 5-HT2A receptor in that location.[22] Another study has found that healthy subjects with a high neuroticism score tend to have higher DASB binding in the thalamus; DASB is a ligand that binds to the serotonin transporter protein.[23]

Another neuroimaging study using magnetic resonance imaging to measure brain volume found that the brain volume was negatively correlated to NEO PI-R neuroticism when correcting for possible effects of intracranial volume, sex, and age.[24]

The results of one study found that, on average, women score moderately higher than men on neuroticism. This study examined sex differences in the ‘Big Five’ personality traits across 55 nations. It found that across the 55 nations studied, the most pronounced difference was in neuroticism.[33] This study found that in 49 of the 55 nations studied, women scored higher in neuroticism than men. In no country did men report significantly higher neuroticism than women.

Neuroticism, along with other personality traits, has been mapped across states in the USA. People in eastern states such as New York, New Jersey, West Virginia, and Mississippi tend to score high on neuroticism, whereas people in many western states, such as Utah, Colorado, South Dakota, Oregon, and Arizona score lower on average. People in states that are higher in neuroticism also tend to have higher rates of heart disease and lower life expectancy.[34]

One of the theories regarding evolutionary approaches to depression focuses on neuroticism. A moderate amount of neuroticism may provide benefits, such as increased drive and productivity, due to greater sensitivity to negative outcomes. Too much, however, may reduce fitness by producing, for example, recurring depressions. Thus, evolution will select for an optimal amount and most people will have neuroticism near this optimum. However, because neuroticism likely has a normal distribution in the population, a minority will be highly neurotic.[35]

VIA Inventory of Strengths (VIA-IS)

Classification of strengths Wisdom and Knowledge: creativity, curiosity, judgment, love of learning, perspective Courage: bravery, perseverance, honesty, zest Humanity: love, kindness, social intelligence Justice: teamwork, fairness, leadership Temperance: forgiveness, humility, prudence, self-regulation Transcendence: appreciation of beauty and excellence, gratitude, hope, humor, spirituality[3] The VIA Inventory of Strengths (VIA-IS), formerly known as the “Values in Action […]

Classification of strengths

  1. Wisdom and Knowledge: creativity, curiosity, judgment, love of learning, perspective
  2. Courage: bravery, perseverance, honesty, zest
  3. Humanity: love, kindness, social intelligence
  4. Justice: teamwork, fairness, leadership
  5. Temperance: forgiveness, humility, prudence, self-regulation
  6. Transcendence: appreciation of beauty and excellence, gratitude, hope, humor, spirituality[3]

The VIA Inventory of Strengths (VIA-IS), formerly known as the “Values in Action Inventory,” is a psychological assessment measure designed to identify an individual’s profile of character strengths. It was created by Christopher Peterson and Martin Seligman, well-known researchers in the field of positive psychology, in order to operationalize theirCharacter Strengths and Virtues Handbook (CSV).[1] The CSV is the positive psychology counterpart to the Diagnostic and Statistical Manual of Mental Disorders (DSM) used in traditional psychology.[1] Unlike the DSM, which scientifically categorizes human deficits and disorders, the CSV classifies positive human strengths.[2] Moreover, the CSV is centered on helping people recognize and build upon their strengths. This aligned with the overall goal of the positive psychology movement, which aims to make people’s lives more fulfilling, rather than simply treating mental illness.[2] Notably, the VIA-IS is the tool by which people can identify their own positive strengths and learn how to capitalize on them.[2]

As a relatively new field of research, positive psychology lacked a common vocabulary for discussing measurable positive traits before 2004.[1] Traditional psychology benefited from the creation of DSM, as it provided researchers and clinicians with the same set of language from which they could talk about the negative. As a first step in remedying this disparity between tradition and positive psychology, Peterson and Seligman set out to identify, organize and measure character.

Peterson & Seligman began by defining the notion of character as traits that are possessed by an individual and are stable over time, but can still be impacted by setting and thus are subject to change.[1] The researchers then started the process of identifying character strengths and virtues by brainstorming with a group of noted positive psychology scholars. Then, Peterson & Seligman examined ancient cultures (including their religions, politics, education and philosophies) for information about how people in the past construed human virtue. The researchers looked for virtues that were present across cultures and time. Six core virtues emerged from their analysis: courage, justice, humanity, temperance, transcendence and wisdom.

Next, Peterson and Seligman proposed a model of classification which includes horizontal and vertical components. The hierarchical system is modeled after the Linnaean classification of species, which ranges from a specific species to more general and broad categories. The scientists stated the six core values are the broadest category and are, “core characteristics valued by moral philosophers and religious thinkers” (p. 13).[1] Peterson and Seligman then moved down the hierarchy to identifying character strengths, which are, “the psychological processes or mechanisms that define the virtues” (p. 13).[1]

The researchers began the process of identifying individual character strengths by brainstorming with a group of noted positive psychology scholars.[1] This exercise generated a list of human strengths, which were helpful when consulting with Gallup Organization. Peterson and Seligman then performed an exhaustive literature search for work that directly addresses good character in the domains of, “psychiatry, youth development, philosophy and psychology” (p. 15). Some individuals who influenced Peterson and Seligman’s choice of strengths include: Abraham Maslow, Erik Erikson, Ellen Greenberger, Marie Jahoda, Carol Ryff, Michael Cawley, Howard Gardner, Shalom Schwartz. In an effort to leave no stone unturned, the researchers also looked for virtue-laden messages in popular culture. For example, the researchers examined Hallmark greeting cards, personal ads, graffiti, bumper stickers and profiles of Pokémon characters.

After identifying dozens of ‘candidate strengths’, the researchers needed to find a way to further refine their list. Therefore, Peterson & Seligman developed a list of 10 criteria (e.g., strengths must contribute to a sense of a fulfilling life, must be intrinsically valuable) to help them select the final 24 strengths for the CSV (see CSV for complete list of criteria). Approximately half of the strengths included in the CSV meet all 10 criteria, and half do not.[1] By looking for similarities between candidate strengths, the researchers distributed 24 character strengths between six virtue categories. Only after creating this a priori organization of traits, the researchers performed, “an exploratory factor analysis of scale scores using varimax rotation,” (p. 632) from which five factors emerged.[1] Peterson & Seligman state that they are not as concerned with how the 24 strengths are grouped into virtue clusters because, in the end, these traits are mixed together to form the character of a person.

Only 3 studies have checked the factor structure of the CSV, on which the VIA-IS is based.[1][9][10]

Using a second order factor analysis, Macdonald & colleagues (2008) found that the 24 strengths did not fit into the 6 higher order virtues model proposed in the CSV. None of the clusters of characters strengths that they found resembled the structure of the 6 virtue clusters of strengths. The researchers noted that many of the VIA character strengths cross-loaded onto multiple factors. Rather, the strengths were best represented by a one and four factor model. A one factor model would mean that the strengths are best accounted for by, “one overarching factor,” such as a global trait of character (p. 797).[9] A four factor model more closely resembles the ‘Big Five’ model of personality. The character strengths in the four factor model could be organized into the following four groups: Niceness, Positivity, Intellect and Conscientiousness.

Peterson and Seligman (2004) conducted a factor analysis and found that a five factor model, rather than their 6 hierarchical virtues model, best organized the strengths. Their study, however, did not include five of the character strengths in the results of their analysis. The researchers most likely did this because their results were plagued by the problem of strengths cross-loading on to multiple factors, similar to what occurred in Macdonald and colleagues (2008) study.[10] Clearly, empirical evidence casts doubt on the link proposed by Peterson & Seligman (2004) between the 24 strengths and associated 6 higher order virtues.

Brdar & Kashdan (2009) used more precise statistical tools to build upon the findings of the two earlier studies. They found that a four factor model (Interpersonal Strengths, Vitality, Fortitude and Cautiousness) explained 60% of the variance. One large, overarching factor explained 50% of the variance. The four factors found by Brdar and Kashdan (2009) are similar to the four factors found by Macdonald and colleagues (2008). Once again, the Brdar and Kashdan found that the 24 strengths did not fall into the 6 higher order virtues proposed by Peterson and Seligman (2004). The correlations found between many of the strengths demonstrates that each strength is not distinct, which contradicts the claims made by the creators of the VIA-IS.

Caution should be taken in interpreting the results from these three studies as their samples differ in age and country of origin.[10]


Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic chemical in the catecholamine family that functions in the human brain and body as a hormone and neurotransmitter. The name “noradrenaline,” derived from Latin roots meaning “at/alongside the kidneys,” is more commonly used in the United Kingdom; in the United States, “norepinephrine,” derived from […]

Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic chemical in the catecholamine family that functions in the human brain and body as a hormone and neurotransmitter. The name “noradrenaline,” derived from Latin roots meaning “at/alongside the kidneys,” is more commonly used in the United Kingdom; in the United States, “norepinephrine,” derived from Greek roots having that same meaning, is usually preferred.[1] “Norepinephrine” is also the International Nonproprietary Namegiven to the compound.[2] Regardless of which name is used for the substance itself, parts of the body that produce or are affected by it are referred to as noradrenergic.

Norepinephrine is synthesized and released by the central nervous system, and also by a division of the autonomic nervous systemcalled the sympathetic nervous system. In the brain, norepinephrine is produced in closely packed brain cell neurons or nuclei that are small yet exert powerful effects on other brain areas. The most important of these nuclei is the locus coeruleus, located in thepons. In the sympathetic nervous system, norepinephrine is used as a neurotransmitter by sympathetic ganglia located near thespinal cord or in the abdomen, and it is also released directly into the bloodstream by the adrenal glands as sympathetic effector organs. Regardless of how and where it is released, norepinephrine acts on target cells by binding to and activating noradrenergic receptors located on the cell surface.

The general function of norepinephrine is to mobilize the brain and body for action. Norepinephrine release is lowest during sleep, rises during wakefulness, and reaches much higher levels during situations of stress or danger, in the so-called fight-or-flight response. In the brain, norepinephrine increases arousal and alertness, promotes vigilance, enhances formation and retrieval of memory, and focuses attention; it also increases restlessness and anxiety. In the rest of the body, norepinephrine increases heart rate and blood pressure, triggers the release of glucose from energy stores, increases blood flow to skeletal muscle, reduces blood flow to the gastrointestinal system, and promotes voiding of the bladder and large intestine.

A variety of medically important drugs work by altering the actions of norepinephrine systems. Norepinephrine itself is widely used as an injectable drug for the treatment of critically low blood pressure. Beta blockers, which counter some of the effects of norepinephrine, are frequently used to treat glaucoma, migraine, and a range of cardiovascular problems. Alpha blockers, which counter a different set of norepinephrine effects, are used to treat several cardiovascular and psychiatric conditions. Alpha-2 agonistsoften have a sedating effect, and are commonly used as anesthesia-enhancers in surgery, as well as in treatment of drug or alcohol dependence. Many important psychiatric drugs exert strong effects on norepinephrine systems in the brain, resulting in side-effects that may be helpful or harmful.

Stanford’s Robert Sapolsky On Depression

Published on May 25, 2014 (edited for improved sound: noise and stereo issues, and miscellaneous parts taken out) Stanford Professor Robert Sapolsky, posits that depression is the most damaging disease that you can experience. Right now it is the number four cause of disability in the US and it is becoming more common. Sapolsky states […]

Published on May 25, 2014
(edited for improved sound: noise and stereo issues, and miscellaneous parts taken out)

Stanford Professor Robert Sapolsky, posits that depression is the most damaging disease that you can experience. Right now it is the number four cause of disability in the US and it is becoming more common. Sapolsky states that depression is as real of a biological disease as is diabetes.


The neurotransmitter serotonin is involved in regulating many important physiological (body-oriented) functions, including sleep, aggression, eating, sexual behavior, and mood. Serotonin is produced by serotonergic neurons. Current research suggests that a decrease in the production of serotonin by these neurons can cause depression in some people, and more specifically, a mood state that can cause some people to feel suicidal.

In the 1960s, the “catecholamine hypothesis” was a popular explanation for why people developed depression. This hypothesis suggested that a deficiency of the neurotransmitter norepinephrine (also known as noradrenaline) in certain areas of the brain was responsible for creating depressed mood. More recent research suggests that there is indeed a subset of depressed people who have low levels of norepinephrine. For example, autopsy studies show that people who have experienced multiple depressive episodes have fewer norepinephrinergic neurons than people who have no depressive history. However, research results also tell us that not all people experience mood changes in response to decreased norepinephrine levels. Some people who are depressed actually show hyperactivity within the neurons that produce norepinephrine. More current studies suggest that in some people, low levels of serotonin trigger a drop in norepinephrine levels, which then leads to depression.

Another line of research has investigated linkages between stress, depression, and norepinephrine. Norepinephrine helps our bodies to recognize and respond to stressful situations. Researchers suggest that people who are vulnerable to depression may have a norepinephrinergic system that doesn’t handle the effects of stress very efficiently.

The neurotransmitter dopamine is also linked to depression. Dopamine plays an important role in regulating our drive to seek out rewards, as well as our ability to obtain a sense of pleasure. Low dopamine levels may in part explain why depressed people don’t derive the same sense of pleasure out of activities or people that they did before becoming depressed.