On the Influence of Serotonin on Social Behavior (Literature Review)
Part 1
Increased serotonin activity in the CNS not only reduces anxiety and depression, while simultaneously impairing some cognitive functions due mainly to its blocking effect on dopamine, norepinephrine, and acetylcholine, but also has a substantial effect on social behavior. In particular, higher CNS serotonin activity leads to reduced aggressiveness (especially – impulsive aggressiveness), shifts behavior toward avoiding harm to another person, increases behavioral compliance, increases the predisposition toward cooperation (cooperative behavior), increases sensitivity to punishment, and reduces the predisposition toward risky behavior. WHAT EVIDENCE IS THERE FOR THIS?
BRIEF LITERATURE REVIEW:
A literature review discussing genetic polymorphisms of the serotonin system and their relationship to social cognition and behavior can be found here:
Skuse, D. 2006. Genetic influences on the neural basis of social cognition. Philos. Trans. R. Soc. B: Biol. Sci. 361: 2129–2141.
A comprehensive review of the relationship between serotonin and social behavior (in both animals and humans) can be found here:
Kiser, D. et al. 2012. The reciprocal interaction between serotonin and social behaviour. Neurosci. Biobehav. Rev. 36: 786–798.
A literature review of the influence of serotonin on social behavior, narrowly focused specifically on studies conducted in humans using controlled experimental manipulations of the serotonin system in the laboratory, can be found here:
Siegel, J. Z., & Crockett, M. J. How serotonin shapes moral judgment and behavior. Ann. N.Y. Acad. Sci. 1299 (2013) P: 42–51; 2013. The Authors. Annals of the New York Academy of Sciences 51 published by Wiley Periodicals Inc. on behalf of The New York Academy of Sciences. nyaspubs.onlinelibrary.wiley.com/doi/pdf/10…
Here and now we offer you a brief synopsis of the last of the literature reviews named above. The main conclusion to which we will ultimately lead is that serotonin influences social behavior by changing social preferences in a positive direction, increasing the value people place on others’ outcomes (that is, aggression and selfishness decrease, while, conversely, behavioral compliance and cooperativeness increase).
Some of the works reviewed use three moral dilemmas that are standard in contemporary psychological and neurophysiological experimental research on human moral behavior. These are the “trolley dilemma,” the “prisoner’s dilemma,” and the “ultimatum game” (UG). To make clear what is being discussed, we will recall their essence.
THE CLASSICAL FORMULATION OF THE “PRISONER’S DILEMMA” IS AS FOLLOWS: Two criminals — A and B — are caught at approximately the same time for similar crimes. There are grounds to believe that they acted in collusion, and the police, having isolated them from each other, offer each the same deal: if one testifies against the other while the other remains silent, the first is released for assisting the investigation, while the second receives the maximum prison term (10 years). If both remain silent, their offense is prosecuted under a less serious charge, and each is sentenced to six months in prison. If both testify against each other, they receive the minimum term (2 years each). Each prisoner chooses whether to remain silent or testify against the other. However, neither knows exactly what the other will do. What will happen? The subject is asked to choose a course of action as the prisoner. This is a fundamental problem in game theory according to which rational players will not always cooperate with one another, even when doing so is in their interests. If each player (“prisoner”) maximizes his own payoff without concern for the benefit of others, then betraying his companion proves to be the most advantageous strategy.
Consider the reasoning of one of the prisoners from the standpoint of egocentric behavior. If the partner remains silent, it is better to betray him and go free (otherwise — six months in prison). If the partner testifies, it is better to betray him as well and testify against him in order to receive 2 years (otherwise — 10 years) in prison. The strategy “testify” strictly dominates the strategy “remain silent.” The other prisoner likewise arrives at the same conclusion.
From the standpoint of the cooperative group (these two prisoners), by contrast, the best option is to cooperate with each other, jointly remain silent, and receive only six months each, since this reduces the total term of imprisonment. Any other decision will be less advantageous.
THE MORAL TROLLEY DILEMMA. A loaded trolley with failed brakes is racing along the rails and threatens to crush flat a large group of miners gathered at the end of the drift. In the first “mild” version of the dilemma, the subject has a choice – whether to press a button that will switch the trolley onto another track, where it will run over only one miner (who, however, would have remained alive if the subject had done nothing). In the second, “hard” version of the dilemma (which is also more emotion-evoking and additionally requires a direct physical act of violence against another person), the subject’s choice is harsher. Instead of pressing a button, one must push a fat worker onto the rails with one’s own hands in order to stop the trolley with his body and thereby save many more lives. The question is: what decision will the subject choose? To act or not to act? People who show the strongest physiological reactions to demonstrations of acts of violence are least likely to approve harming one person in order to save many others (in both versions of the dilemma, mild and hard) [32]
32. Cushman, F. & L. Young. 2011. Patterns of moral judgment derive from nonmoral psychological representations. Cogn. Sci. 35: 1052–1075.
THE ULTIMATUM GAME consists in the experimenters offering two players (who cannot see one another and remain anonymous to each other) a certain sum of money at each stage, which the players must divide between themselves. Moreover, bargaining is not allowed; there is only one offer, to which an immediate response must be made. The proposer must offer a division of the sum to the responder, who must decide either to accept or reject the offer. If the responder accepts the offer, both players are paid; if he rejects it, neither is paid. Completely selfish respondents will accept any nonzero offer, but respondents who prefer fairness or reciprocity will reject offers considered unfair or insulting —usually less than 30% of the stake. The dilemma of this game consists in balancing several different motivations. One – the desire to maximize one’s own total income. Another – the desire to punish a dishonest partner who continually pulls the blanket toward himself. A third – the desire not to offend the partner (both for moral reasons and in order not to provoke further aggression from him against oneself, which could reduce one’s income)
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Serotonin is more concentrated in certain brain structures than in others. Anatomical studies illustrate
the highest concentrations of serotonin in various limbic structures, such as the cingulate, entorhinal, insular, and temporal regions, as well as the ventral and pallidal regions of the striatum (corpus striatum) [1] and the medial orbitofrontal cortex. [2] Notably, this
set of regions has a striking resemblance to the so-called social brain [3] -those regions that support social cognition and decision-making.
1. Varnas, K., C. Halldin & H. Hall. 2004. Autoradiographic distribution of serotonin transporters and receptor subtypes in human brain. Hum. Brain Mapp. 22: 246–260.
2. Way, B.M. et al. 2007. Architectonic distribution of the serotonin transporter within the orbitofrontal cortex of the vervet monkey. Neuroscience 148: 937–948.
3. Sanfey, A.G. 2007. Social decision-making: insights from game theory and neuroscience. Science 318: 598–602.
Serotonin functions are generally positively associated with prosocial behavior, such as caregiving (care), cooperation, belonging (social inclusion), and are generally negatively associated and correlated with antisocial behavior such as aggression or social isolation. [12-19]
12. Doudet, D. et al. 1995. Cerebral glucose metabolism, CSF 5-HIAA levels, and aggressive behavior in rhesus monkeys. Am. J. Psychiatr. 152: 1782–1787.
13. Higley, J. et al. 1996. Stability of interindividual differences in serotonin function and its relationship to severe aggression and competent social behavior in rhesus macaque females. Neuropsychopharmacology 14: 67–76.
14. Higley, J.D. et al. 1992. Cerebrospinal fluid monoamine and adrenal correlates of aggression in free-ranging rhesus monkeys. Arch. Gen. Psychiatr. 49: 436.
15. Raleigh, M. et al. 1980. Serotonergic influences on the social behavior of vervet monkeys (Cercopithecus aethiops sabaeus). Exp. Neurol. 68: 322–334.
16. Linnoila, M. et al. 1983. Low cerebrospinal fluid 5-hydroxyindoleacetic acid concentration differentiates impulsive from nonimpulsive violent behavior. Life Sci. 33: 2609–2614.
17. Krakowski, M. 2003. Violence and serotonin: influence of impulse control, affect regulation, and social functioning. J. Neuropsychiatr. Clin. Neurosci. 15: 294–305.
18. Moskowitz, D. et al. 2001. The effect of tryptophan on social interaction in everyday life-a placebo-controlled study. Neuropsychopharmacology 25: 277–289.
19. Knutson, B. et al. 1998. Selective alteration of personality and social behavior by serotonergic intervention. Am. J. Psychiatr. 155: 373–379.
A recent meta-analysis covering 175 independent samples and more than 6500 experimental participants found a reliable inverse relationship between serotonin and aggression, but was unable to identify specific factors explaining the heterogeneity of the study results. [23]
23. Duke, A.A.et al. 2013. Revisiting the serotonin—aggression relation in humans: a meta-analysis. Psychol. Bull. Feb. 4.
Early studies in rats showed that global depletion of serotonin in the brain made them insensitive to punishment [45].
45. Tye, N., B. Everitt & S.D. Iversen. 1977. 5-Hydroxytryptamine and punishment. Nature 268: 741–743.
In humans, serotonin levels are positively correlated with personality traits involving avoidance of causing harm to other people [46,47].
46. Gerra, G.et al. 2000. Neuroendocrine correlates of temperamental traits in humans. Psychoneuroendocrinology 25(5): 479–496.
47. Hansenne, M. & M. Ansseau. 1999. Harm avoidance and serotonin. Biol. Psychol. 51: 77–81.
SEROTONIN increases fear of punishment, strengthens avoidance behavior, and inhibits dangerous approach behavior.
One contemporary hypothesis is that serotonin plays a key role at the intersection of aversion and inhibition. Under normal conditions, the presence of adverse outcomes leads to behavioral inhibition, which may manifest as a reduced probability of acting or a slowing of response time.
Moderate depletion of brain serotonin in humans abolishes this aversion-induced behavioral inhibition, thereby increasing impulsivity [4,55,56], which suggests that serotonin is important for promoting behavioral suppression or withholding behavior in the face of aversive predictions.
Note that behavioral inhibition in response to adverse outcomes reflects at least two simultaneous processes: instrumental adverse predictions linking actions to immediate outcomes, and aversive predictions based on Pavlovian conditioned reflexes linking stimuli and contexts to outcomes. Recent evidence suggests that serotonin mediates responses to the latter, Pavlovian process; serotonin depletion abolishes response inhibition in the presence of aversive stimuli, regardless of whether the responses themselves led to punishment [56].
4. Crockett, M.J., L. Clark & T.W. Robbins. 2009. Reconciling the role of serotonin in behavioral inhibition and aversion: acute tryptophan depletion abolishes punishment-induced inhibition in humans. J. Neurosci. 29: 11993–11999.
55. Crockett, M. et al. 2011. Converging evidence for central 5-HT effects in acute tryptophan depletion. Mol. Psychiatr. 17: 121–123.
56. Crockett, M.J. et al. 2012. Serotonin modulates the effects of pavlovian aversive predictions on response vigor. Neuropsychopharmacology 37(10): 2244–2252.
Neuroimaging studies of moral judgments have shown that when situations involving a harmful action directed against another person are perceived or mentally simulated, this engages brain regions with a high density of serotonin, including the anterior cingulate cortex, ventromedial prefrontal cortex (vmPFC), amygdala, and striatum. [34,40,42,57].
34. Greene, J.D. et al. 2001. An fMRI investigation of emotional engagement in moral judgment. Science 293: 2105–2108.
40. Greene, J.D. et al. 2004. The neural bases of cognitive conflict and control in moral judgment. Neuron 44: 389.
42. Shenhav, A. & J.D. Greene. 2010. Moral judgments recruit domain-general valuation mechanisms to integrate representations of probability and magnitude. Neuron 67: 667–677.
57. Kedia, G. ´ et al. 2008. An agent harms a victim: a functional magnetic resonance imaging study on specific moral emotions. J. Cogn. Neurosci. 20: 1788–1798.
Patients with damage to the vmPFC show impairments in moral judgments and in normal harm aversion in the sense that they,
are more likely to approve harming one person in order to save many others. [58,59]
58. Koenigs, M. et al. 2007. Damage to the prefrontal cortex increases utilitarian moral judgements. Nature 446: 908–911.
59. Ciaramelli, E.et al. 2007. Selective deficit in personal moral judgment following damage to ventromedial prefrontal cortex. Soc. Cogn. Affect. Neurosci. 2: 84–92.
SEROTONIN INTENSIFIES AVERSION TO HARMING A SPECIFIC PERSON IN MORAL JUDGMENT.
Crockett et al. [60] tested this hypothesis by investigating the effect of the selective serotonin reuptake inhibitor (SSRI) citalopram on moral judgments across a series of moral dilemmas. Citalopram enhances serotonin function by blocking its reuptake at the presynaptic terminal after release, thereby prolonging its action in the synapse. Compared with both atomoxetine (a norepinephrine reuptake inhibitor) and placebo, citalopram reduced the likelihood that people would approve harming one person (a specific person located nearby) in order to save many others (more abstract and nameless to the actor). In other words, citalopram intensified aversion to harming a specific nearby person in moral judgment [60]. The serotonin reuptake inhibitor citalopram reduced the likelihood that subjects would approve harming one person in order to save many others, especially when the harm was emotionally salient. (that is, in the version of the well-known trolley moral dilemma in which one must not merely press a button, but push one person onto the tracks with one’s own hands in order to save many others).
However, subjects with lower empathy scores (measured using the Interpersonal Reactivity Index, questionnaire [61]) showed almost no effect of citalopram on moral judgments; the overall drug effect in the group was almost entirely due to subjects with higher empathy scores, who showed a strong effect of citalopram on judgments. That is, subjects with high levels of empathy may have a higher baseline level of harm aversion, which was only further intensified by citalopram.
60. Crockett, M.J. et al. 2010. Serotonin selectively influences moral judgment and behavior through effects on harm aversion. Proc. Natl. Acad. Sci. 107: 17433–17438.
61. Davis, M.H., C. Luce & S.J. Kraus. 1994. The heritability of characteristics associated with dispositional empathy. J. Pers. 62: 369–391.
See continuation below…
nyaspubs.onlinelibrary.wiley.com/doi/pdf/10…
Part 2 (continuation of the review):
Recall the evidence indicating that serotonin is critically important for translating aversion to situations unacceptable for moral reasons (that is, conditioned-reflex signals) into behavioral inhibition. [56]
If a similar process unfolds as subjects deliberate over moral dilemmas, then enhancement of serotonin function may increase subjects’ sensitivity to aversive conditioned-reflex signals present in descriptions of moral dilemmas, making subjects more averse to the proposed harmful action and more inclined to disapprove of it. The results described by Crockett et al. [60] are consistent with this proposal.
56. Crockett, M.J. et al. 2012. Serotonin modulates the effects of pavlovian aversive predictions on response vigor. Neuropsychopharmacology 37(10): 2244–2252.
60. Crockett, M.J. et al. 2010. Serotonin selectively influences moral judgment and behavior through effects on harm aversion. Proc. Natl. Acad. Sci. 107: 17433–17438.
Cooperative behavior in social dilemmas has been associated with serotonin function. One study showed,
that after 2 weeks of treatment with citalopram, participants behaved selfishly significantly less often in a modified version of the prisoner’s dilemma
that allowed participants, at their choice, to act selfishly, cooperatively, or benevolently. [66]
A moderate reduction in brain serotonin levels produced the opposite effect, that is, it reduced cooperative cooperation in the prisoner’s dilemma. [67] These results indicate that serotonin function is associated with positive social preferences, that is, with assigning positive value, for oneself, to the outcomes of others as well.
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66. Tse, W.S. & A.J. Bond. 2002. Difference in serotonergic and noradrenergic regulation of human social behaviours. Psychopharmacology 159: 216–221.
67. Wood, R.M. et al. 2006. Effects of tryptophan depletion on the performance of an iterated Prisoner’s Dilemma game in healthy adults. Neuropsychopharmacology 31: 1075–1084.
SEROTONIN INCREASES COMPLIANCE IN NEGOTIATIONS, INCLUDING IN RESPONSE TO UNFAIR OFFERS
Preferences regarding negative reciprocity and fairness have been extensively studied using the ultimatum game (UG). To recall, the UG consists of two players, a proposer and a responder, who must agree on a way to divide a sum of money, otherwise neither of them receives anything. The proposer must offer a division of the sum to the responder, who must decide either to accept or reject the offer. If the responder accepts the offer, both players are paid; if he rejects it, neither is paid. Completely selfish respondents will accept any nonzero offer, but respondents who prefer fairness or reciprocity will reject offers considered unfair—usually less than 30% of the stake.
Several studies have examined the relationship between serotonin function and respondents’ behavior in the UG. Emanuele et al. [69] reported that serotonin levels in platelets were inversely correlated with the frequency with which respondents rejected received “unfair” offers. However, given that serotonin does not cross the blood-brain barrier, plasma levels may not correspond to central serotonin levels. A more recent study showed that the density of serotonin transporters in the dorsal raphe nucleus—an indirect measure of active serotonin function—was also inversely correlated with respondents’ rejection frequency. [70] Although these studies already suggest an association between serotonin and preferences regarding fairness and reciprocity, direct pharmacological manipulations have additionally supported these claims with causal evidence.
Crockett et al. [71] investigated the effect of reduced serotonin availability on respondents’ behavior in the UG. Respondents were more likely to reject unfair offers after depletion of central serotonin than after placebo. [71] A subsequent study [72] tested whether, conversely, ENHANCEMENT of serotonin function using citalopram (SSRI, serotonin reuptake inhibitor) would have the opposite effect on rejection behavior. Compared with both placebo and the norepinephrine reuptake inhibitor atomoxetine, citalopram indeed reduced the frequency of respondents’ rejections of “unfair offers,” rejections motivated by a desire to punish the partner (and themselves at the same time), in the UG. [72]
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69. Emanuele, E.et al. 2008. Relationship between platelet serotonin content and rejections of unfair offers in the ultimatum game. Neurosci. Lett. 437: 158–161.
70. Takahashi, H.et al. 2012. Honesty mediates the relationship between serotonin and reaction to unfairness. Proc. Natl. Acad. Sci. 109: 4281–4284.
71. Crockett, M.J. et al. 2008. Serotonin modulates behavioral reactions to unfairness. Science 320: 1739.
72. Crockett, M.J. et al. 2010. Impulsive choice and altruistic punishment are correlated and increase in tandem with serotonin depletion. Emotion 10: 855.
Previous neuroimaging studies have shown that fair social exchanges stimulate activity in the ventral striatum and medial PFC [74-76], so it can be assumed that activity in these regions reflects preferences regarding fairness.
Crockett et al. [73] investigated the effect of serotonin depletion on responses of the ventral striatum and medial PFC to receiving fair offers in the UG and found that serotonin depletion blunts the response of these brain regions to fairness. Thus, serotonin levels appear to be positively correlated with (neural) preferences regarding fairness.
Meanwhile, negative reciprocity (this is when a partner’s unfair offers elicit a reaction of indignation and are rejected, with a monetary loss for both) has been associated with activation in the dorsal (that is, posterior) striatum. Neuroimaging studies have found activation in the dorsal striatum during retaliatory actions both after personally receiving an unfair offer and after passively observing the unfair behavior of other players. [77,78]. This activity was observed only in cases of effective punishment of a violator of fairness norms; symbolic retaliatory actions (such as verbal abuse) that did not reduce the norm violator’s payoff did not stimulate activity in the dorsal striatum [78] In addition, the magnitude of dorsal striatal activity was directly correlated with the amount the subject was willing to pay in order to punish the violator.
Taken together, these results indicate that the dorsal striatum signals the instrumental value of negative reciprocity, which is consistent with its broader role in goal-directed reward processing. [79]
Crockett et al. [73] demonstrated that serotonin depletion enhanced responses in the dorsal striatum during rejection of unfair offers in the ultimatum game (UG) compared with placebo. This effect was characteristic of trials in which subjects actively rejected unfair offers, compared with trials in which subjects simply received unfair offers but had no opportunity to reject them. Moreover, the effect of serotonin manipulation on dorsal striatal activity was positively correlated with the effect of serotonin manipulation on behavior involving rejection of unfair offers in the game. These results indicate that the dorsal striatum plays a causal role in negative reciprocity and that serotonin levels are negatively correlated with neural and behavioral preferences regarding negative reciprocity. That is, the less serotonin there is, the more likely the player is to want to punish the partner who violated the norm, even to the detriment of his own economic interests.
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73. Crockett, M.J. et al. 2013. Serotonin modulates striatal responses to fairness and retaliation in humans. J. Neurosci. 33: 3505–3513.
74. Tabibnia, G., A.B. Satpute & M.D. Lieberman. 2008. The sunny side of fairness preference for fairness activates reward circuitry (and disregarding unfairness activates selfcontrol circuitry). Psychol. Sci. 19: 339–347.
75. Zaki, J. & J.P. Mitchell. 2011. Equitable decision making is associated with neural markers of intrinsic value. Proc. Natl. Acad. Sci. 108: 19761–19766.
76. Tricomi, E. et al. 2010. Neural evidence for inequality-averse social preferences. Nature 463: 1089–1091.
77. Strobel, A. et al. 2011. Beyond revenge: neural and genetic bases of altruistic punishment. Neuroimage 54: 671–680.
78. Quervain, D.J.F. et al. 2004. The neural basis of altruistic punishment. Science 305: 1254–1258.
79. O’Doherty, J. et al. 2004. Dissociable roles of ventral and dorsal striatum in instrumental conditioning. Science 304: 452–454.
Thus, serotonin strengthens neural representations of positive social preferences, whereas serotonin depletion shifts neural value computations toward selfish or even negative social preferences. This view is consistent with earlier behavioral studies indicating a positive correlation between serotonin function and prosocial behavior, but goes even further by proposing a model of how serotonin influences the preferences that govern this behavior
Positive social preferences - altruists are willing to sacrifice part of their own benefit for the benefit of others. Negative social preferences - spiteful people are willing to sacrifice part of their own benefit in order to reduce the benefits of others and punish others by causing them harm. It should be assumed that serotonin shifts social preferences in a positive (altruistic) direction.
Thus, Crockett et al. [71,73] demonstrated that serotonin depletion intensifies negative social preferences under conditions of disadvantageous inequality, whereas increased serotonin reduces negative social preferences in this setting.
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71. Crockett, M.J. et al. 2008. Serotonin modulates behavioral reactions to unfairness. Science 320: 1739.
73. Crockett, M.J. et al. 2013. Serotonin modulates striatal responses to fairness and retaliation in humans. J. Neurosci. 33: 3505–3513.
Studies have shown that the structure and function of brain regions involved in mentalizing, such as the temporoparietal junction (TPJ) and superior temporal sulcus, may predict positive social preferences and subsequent generosity. [94,95]. Similarly, empathy-related regions such as the anterior insula and anterior cingulate cortex are sensitive to the moral status of other people [96] and correlate with altruistic helping. [97,98]. Thus, it remains an open question whether serotonin modulates moral behavior indirectly by influencing empathic representations in the TPJ, insula, and anterior cingulate cortex, or directly by changing neural computations of social preferences in the striatum and medial PFC. Although initial evidence supports the latter view [73], further work in this area is still needed to understand how individual differences in empathy moderate the influence of serotonin on moral judgments and behavior. [72]
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72. Crockett, M.J. et al. 2010. Impulsive choice and altruistic punishment are correlated and increase in tandem with serotonin depletion. Emotion 10: 855.
73. Crockett, M.J. et al. 2013. Serotonin modulates striatal responses to fairness and retaliation in humans. J. Neurosci. 33: 3505–3513.
94. Morishima, Y. et al. 2012. Linking brain structure and activation in temporoparietal junction to explain the neurobiology of human altruism. Neuron 75: 73–79.
95. Hare, R.D. & C.S. Neumann. 2010. The role of antisociality in the psychopathy construct: comment on Skeem and Cooke (2010). Psychol. Assess. 22: 446–454.
96. Singer, T. et al. 2006. Empathic neural responses are modulated by the perceived fairness of others. Nature 439: 466–469.
97. FeldmanHall, O. et al. 2012. Differential neural circuitry and self-interest in real vs hypothetical moral decisions. Soc. Cogn. Affect. Neurosci. 7: 743–751.
98. Hein, G. et al. 2010. Neural responses to ingroup and outgroup members’ suffering predict individual differences in costly helping. Neuron 68: 149–160.
CONCLUSIONS on the role of serotonin in social status:
High social-group status in male lower primates, but only in males (and in part – also in humans, who are organized in a more socially complex manner), is indeed accompanied by a tendency toward increased serotonin activity in the CNS, including increases in its concentrations in the blood and cerebrospinal fluid.
The relationship between serotonin and social status is bidirectional and reciprocal: high serotonin contributes to acquiring higher social status; in turn, acquired high group status increases serotonin in the individual.
Serotonin is far from the only hormonal agent influencing an individual’s social status. Acquisition of higher dominance ranks is also promoted by elevated testosterone (which maintains aggressiveness at an appropriate level), vasopressin, in women – also oxytocin, and in all sexes – their lower cortisol status. Group status is also influenced by (or reflected in) CNS concentrations of a number of recently discovered specific neuropeptides. Thus, it is not possible to establish an unambiguous direct relationship between serotonin levels and social status, although a positive correlation between them does exist.
It should be remembered that although the concept of social status within a group is fairly universal in animals, in humans at least two different forms of social dominance should be distinguished. One of them is based on authority within a small group in which everyone knows one another by sight. Here, apparently, the role of high serotonin is maximal, since it gives a person’s behavior confidence, optimism, equanimity, and affiliativeness (that is, the ability to form warm, trusting, emotionally significant relationships with other people), increases readiness to care for others and to share (moreover - from the position of a self-confident strong person), and increases the Te and Fi components in behavior (that is – the “Serious” components in the socionic sense). All these factors can undoubtedly contribute to increasing a person’s authority in the group within the framework of intergroup interaction, that is, they lead to growth of his intragroup status. The second form of social dominance is more common in large human communities (from large corporations to states); it is despotic and based on instilling fear among subordinates. Within such a strategy, the dominant individual requires strength and cruelty rather than affiliativeness, ambition and egocentric lust for power rather than responsibility for others, and the role, for example, of a high testosterone level in such a case proves far more necessary and important.
Even within the interaction of serotonin alone with social-group status, it should be remembered that the issue is not merely a formal increase or decrease in the activity of the serotonergic system as a whole, but primarily a restructuring of the relationships among its components, when a change in status is accompanied by changes in the balance of expression of different types of serotonin receptors (of which there are about two dozen). The serotonin system serves as an intermediary between environmental resources and the state of the organism. It regulates the state of the organism in such a direction as to adapt it optimally to the state of the currently available environmental resources. As a result, its effect on the organism is not single-factor but multifactorial – through changes in the balance of expression of numerous types of serotonin receptors on neurons and other cells of the organism that differ greatly in their functions.
Overall, in humans, “a lot of serotonin” (the principal factor in its action) produces not only a subjective sense of well-being and confidence, but also a more general subjective sense of the availability and even abundance of existing resources (which, generally speaking, is the cause of the feeling of serene well-being). Elevated serotonin overall leads to some reduction in exploratory activity, to a conservative orientation toward preservation rather than search and acquisition, elevates mood and reduces anxiety, improves posture and straightens the back, makes the gaze more direct, makes a person more good-natured, creates a sense of confidence, reduces fears, increases approach behavior and decreases avoidance behavior, reduces envy, increases social motivation to share resources with close others, and also increases motivation to occupy higher status levels in society (because “why not,” since resources are available and “everything is now accessible”). At the same time, “serotonergic lust for power” looks less like aggression and greedy, conflictual lust for power (that is – more characteristic of testosterone), and more like confidence in one’s right and a constant readiness to decide other people’s fates while taking responsibility for others, and to “sit on the presidium.” In turn, the current serotonin level also depends on the current availability of resources. Specifically, after successful achievements it rises, while after failures and setbacks – it falls (not counting its circadian rhythms). If there is a lot of serotonin – there will also be greater claims to higher status and authority in the group. And the higher the status attained, signaling to the organism its success and access to broader resources, the higher serotonin in turn becomes (until a run of successes is replaced by a prolonged run of failures).
During the conquest of power, a person’s behavior may contain much aggression and adventurism, but after power has been won, their level decreases simultaneously with the rise in serotonin (which registers the success of victory and conquest), while readiness to dispense benefits to close others out of one’s bounty – increases. This, in fact, is the basis, not entirely without reason, for the rather widespread popular opinion that “it is better to let the current bosses remain rather than have new ones; these ones have at least already eaten their fill, and at least something trickles down to us from them.”
The corresponding prediction usually runs aground on rational Beta psychotypes, and especially EIE. The point is that EIE is often characterized by such a profound serotonin deficit that no increase in social status succeeds in compensating for it. Therefore, in particular, in the 1930s the many German and European politicians and political scientists who expected of Hitler that, after the conquest and consolidation of power, “everything would settle down” and his international and domestic policies would become much more capable of reaching agreements, more willing to compromise, and more peace-loving were badly mistaken in their predictions.