Endocrinological effects of social exclusion and inclusion: Experimental evidence for adaptive regulation of female fecundity.

When current conditions are probabilistically less suitable for successful reproduction than future conditions, females may prevent or delay reproduction until conditions improve. Throughout human evolution, social support was likely crucial to female reproductive success. Women may thus have evolved fertility regulation systems sensitive to cues from the social environment. However, current understanding of how psychological phenomena might affect female ovarian function is limited. In this study, we examined whether cues of reduced social support-social ostracism-impact women's hormone production. Following an in-lab group bonding task, women were randomly assigned to a social exclusion (n = 88) or social inclusion (n = 81) condition. After social exclusion, women with low background levels of social support experienced a decrease in estradiol relative to progesterone. In contrast, socially-included women with low background social support experienced an increase in estradiol relative to progesterone. Hormonal changes in both conditions occurred specifically when women were in their mid-to-late follicular phase, when baseline estradiol is high and progesterone is low. Follow-up analyses revealed that these changes were primarily driven by changes in progesterone, consistent with existing evidence for disruption of ovarian function following adrenal release of follicular-phase progesterone. Results offer support for a potential mechanism by which fecundity could respond adaptively to the loss or lack of social support.

Prosocial effects of MDMA: A measure of generosity.

BACKGROUND: 3,4-methylenedioxymethamphetamine (MDMA) produces "prosocial" effects that contribute to its recreational use. Few studies have examined the cognitive and behavioral mechanisms by which MDMA produces these effects. Here we examined the effect of MDMA on a specific prosocial effect, i.e. generosity, using a task in which participants make decisions about whether they or another person will receive money (Welfare Trade-Off Task; WTT). METHODS: The project included one study without drug administration and one with MDMA. In Study 1, we administered the WTT to healthy adults (N = 361) and examined their performance in relation to measures of personality and socioeconomic status. In Study 2, healthy volunteers with MDMA experience (N = 32) completed the WTT after MDMA administration (0, 0.5, or 1.0 mg/kg). RESULTS: As expected, in both studies participants were more generous with a close friend than an acquaintance or stranger. In Study 1, WTT generosity was related to household income and trait Agreeableness. In Study 2, MDMA (1.0 mg/kg) increased generosity toward a friend but not a stranger, whereas MDMA (0.5 mg/kg) slightly increased generosity toward a stranger, especially among female participants. CONCLUSIONS: These data indicate that the WTT is a valuable, novel tool to assess a component of prosocial behavior, i.e. generosity to others. The findings support growing evidence that MDMA produces prosocial effects, but, as with oxytocin, these appear to depend on the social proximity of the relationships. The brain mechanisms underlying the construct of generosity, or the effects of MDMA on this measure, remain to be determined.

Merely opting out of a public good is moralized: an error management approach to cooperation.

People regularly free ride on collective benefits, consuming them without contributing to their creation. In response, free riders are often moralized, becoming targets of negative moral judgments, anger, ostracism, or punishment. Moralization can change free riders' behavior (e.g., encouraging them to contribute or discouraging them from taking future benefits) or it can motivate others, including moralizers, to avoid or exclude free riders; these effects of moralization are critical to sustaining human cooperation. Based on theories of error management and fundamental social domains from evolutionary psychology, we propose that the decision to moralize is a cue-driven process. One cue investigated in past work is observing a person illicitly consume collective benefits. Here, we test whether the mind uses a 2nd cue: merely opting out of contributing. Use of this cue creates a phenomenon of preventive moralization: moralization of people who have not yet exploited collective benefits but who might-or might not--in the future. We tested for preventive moralization across 9 studies using implicit and explicit measures of moralization, a behavioral measure of costly punishment, mediation analyses of the underlying processes, and a nationally representative sample of almost 1,000 U.S. adults. Results revealed that merely opting out of contributing to the creation of exploitable collective benefits--despite not actually exploiting collective benefits-elicited moralization. Results further showed that preventive moralization is not due to the moralization of selfishness or deviance but instead follows from the uncertainty inherent in moralization decisions. These results imply that even people who will never exploit collective benefits can nonetheless be targets of moralization. We discuss implications for social and political dynamics.

When the economy falters, do people spend or save? Responses to resource scarcity depend on childhood environments.

Just as modern economies undergo periods of boom and bust, human ancestors experienced cycles of abundance and famine. Is the adaptive response when resources become scarce to save for the future or to spend money on immediate gains? Drawing on life-history theory, we propose that people's responses to resource scarcity depend on the harshness of their early-life environment, as reflected by childhood socioeconomic status (SES). In the three experiments reported here, we tested how people from different childhood environments responded to resource scarcity. We found that people who grew up in lower-SES environments were more impulsive, took more risks, and approached temptations more quickly. Conversely, people who grew up in higher-SES environments were less impulsive, took fewer risks, and approached temptations more slowly. Responses similarly diverged according to people's oxidative-stress levels-a urinary biomarker of cumulative stress exposure. Overall, whereas tendencies associated with early-life environments were dormant in benign conditions, they emerged under conditions of economic uncertainty.

The Social Cognition of Social Foraging: Partner Selection by Underlying Valuation.

Humans and other animals have a variety of psychological abilities tailored to the demands of asocial foraging, that is, foraging without coordination or competition with other conspecifics. Human foraging, however, also includes a unique element, the creation of resource pooling systems. In this type of social foraging, individuals contribute when they have excess resources and receive provisioning when in need. Is this behavior produced by the same psychology as asocial foraging? If so, foraging partners should be judged by the same criteria used to judge asocial patches of resources: the net energetic benefits they provide. The logic of resource pooling speaks against this. Maintaining such a system requires the ability to judge others not on their short-term returns, but on the psychological variables that guide their behavior over the long-term. We test this idea in a series of five studies using an implicit measure of categorization. Results showed that (1) others are judged by the costs they incur (a variable not relevant to asocial foraging) whereas (2) others are not judged by the benefits they provide when benefits provided are unrevealing of underlying psychological variables (despite this variable being relevant to asocial foraging). These results are suggestive of a complex psychology designed for both social and asocial foraging.

The psychosemantics of free riding: dissecting the architecture of a moral concept.

For collective action to evolve and be maintained by selection, the mind must be equipped with mechanisms designed to identify free riders--individuals who do not contribute to a collective project but still benefit from it. Once identified, free riders must be either punished or excluded from future collective actions. But what criteria does the mind use to categorize someone as a free rider? An evolutionary analysis suggests that failure to contribute is not sufficient. Failure to contribute can occur by intention or accident, but the adaptive threat is posed by those who are motivated to benefit themselves at the expense of cooperators. In 6 experiments, we show that only individuals with exploitive intentions were categorized as free riders, even when holding their actual level of contribution constant (Studies 1 and 2). In contrast to an evolutionary model, rational choice and reinforcement theory suggest that different contribution levels (leading to different payoffs for their cooperative partners) should be key. When intentions were held constant, however, differences in contribution level were not used to categorize individuals as free riders, although some categorization occurred along a competence dimension (Study 3). Free rider categorization was not due to general tendencies to categorize (Study 4) or to mechanisms that track a broader class of intentional moral violations (Studies 5A and 5B). The results reveal the operation of an evolved concept with features tailored for solving the collective action problems faced by ancestral hunter-gatherers.

Familiarity and personal experience as mediators of recall when planning for future contingencies.

In this article, we demonstrate that planning tasks enhance recall when the context of planning (a) is self-referential and (b) draws on familiar scenarios represented in episodic memory. Specifically, we show that when planning tasks are sorted according to the degree to which they evoke memories of personally familiar scenarios (e.g., planning a picnic), recall is reliably superior to tasks that fail to do so (e.g., planning an Arctic trek). We discuss the implications of these findings for planning tasks and their relation to episodic memory.

The financial consequences of too many men: sex ratio effects on saving, borrowing, and spending.

The ratio of males to females in a population is an important factor in determining behavior in animals. We propose that sex ratio also has pervasive effects in humans, such as by influencing economic decisions. Using both historical data and experiments, we examined how sex ratio influences saving, borrowing, and spending in the United States. Findings show that male-biased sex ratios (an abundance of men) lead men to discount the future and desire immediate rewards. Male-biased sex ratios decreased men's desire to save for the future and increased their willingness to incur debt for immediate expenditures. Sex ratio appears to influence behavior by increasing the intensity of same-sex competition for mates. Accordingly, a scarcity of women led people to expect men to spend more money during courtship, such as by paying more for engagement rings. These findings demonstrate experimentally that sex ratio influences human decision making in ways consistent with evolutionary biological theory. Implications for sex ratio effects across cultures are discussed.

The influence of mortality and socioeconomic status on risk and delayed rewards: a life history theory approach.

Why do some people take risks and live for the present, whereas others avoid risks and save for the future? The evolutionary framework of life history theory predicts that preferences for risk and delay in gratification should be influenced by mortality and resource scarcity. A series of experiments examined how mortality cues influenced decisions involving risk preference (e.g., $10 for sure vs. 50% chance of $20) and temporal discounting (e.g., $5 now vs. $10 later). The effect of mortality depended critically on whether people grew up in a relatively resource-scarce or resource-plentiful environment. For individuals who grew up relatively poor, mortality cues led them to value the present and gamble for big immediate rewards. Conversely, for individuals who grew up relatively wealthy, mortality cues led them to value the future and avoid risky gambles. Overall, mortality cues appear to propel individuals toward diverging life history strategies as a function of childhood socioeconomic status, suggesting important implications for how environmental factors influence economic decisions and risky behaviors.

The future-orientation of memory: planning as a key component mediating the high levels of recall found with survival processing.

In a series of papers, Nairne and colleagues have demonstrated that tasks encouraging participants to judge words for relevance to survival led to better recall than did tasks lacking survival relevance. Klein, Robertson, and Delton (2010) presented data suggesting that the future-directed temporal orientation of the survival task (e.g., planning), rather than survival per se, accounts for the good recall found with the task. In the present studies we manipulated the amount of survival and planning processing encouraged by a set of encoding tasks. Participants performed tasks that encouraged processing stimuli for their relevance to (a) both survival and planning, (b) planning, but not survival, or (c) survival but not planning. We predicted, and found, that recall performance associated with tasks encouraging planning (i.e., survival with planning and planning without survival) should exceed tasks that encouraged survival but not planning (i.e., survival without planning). We draw several conclusions. First, planning is a necessary component of the superior recall found in the survival paradigm. Second, memory, from an evolutionary perspective, is inherently prospective--tailored by natural selection to support future decisions and judgements that cannot be known in advance with certainty.

Environmental contingency in life history strategies: the influence of mortality and socioeconomic status on reproductive timing.

Why do some people have children early, whereas others delay reproduction? By considering the trade-offs between using one's resources for reproduction versus other tasks, the evolutionary framework of life history theory predicts that reproductive timing should be influenced by mortality and resource scarcity. A series of experiments examined how mortality cues influenced the desire to have children sooner rather than later. The effects of mortality depended critically on whether people grew up in a relatively resource-scarce or resource-plentiful environment. For individuals growing up relatively poor, mortality cues produced a desire to reproduce sooner--to want children now, even at the cost of furthering one's education or career. Conversely, for individuals growing up relatively wealthy, mortality cues produced a desire to delay reproduction--to further one's education or career before starting a family. Overall, mortality cues appear to shift individuals into different life history strategies as a function of childhood socioeconomic status, suggesting important implications for how environmental factors can influence fertility and family size.

Facing the future: memory as an evolved system for planning future acts.

All organisms capable of long-term memory are necessarily oriented toward the future. We propose that one of the most important adaptive functions of long-term episodic memory is to store information about the past in the service of planning for the personal future. Because a system should have especially efficient performance when engaged in a task that makes maximal use of its evolved machinery, we predicted that future-oriented planning would result in especially good memory relative to other memory tasks. We tested recall performance of a word list, using encoding tasks with different temporal perspectives (e.g., past, future) but a similar context. Consistent with our hypothesis, future-oriented encoding produced superior recall. We discuss these findings in light of their implications for the thesis that memory evolved to enable its possessor to anticipate and respond to future contingencies that cannot be known with certainty.

The functional independence of trait self-knowledge: commentary on Sakaki (2007).

In a recent paper, Sakaki (2007) proposed that Klein and Loftus's conclusion that semantic and episodic trait self-knowledge are functionally independent (e.g., Klein, Babey, & Sherman, 1997; Klein & Loftus, 1993a; Klein, Loftus, Trafton, & Fuhrman, 1992b) was based on questionable assumptions and not supported by the available evidence. In this paper we show that Sakaki (2007) has misinterpreted our position on the independence of self-knowledge, omitted mention of large portions of the relevant research at odds with her contention, and conducted her studies with procedures we explicitly warned against due to interpretive ambiguities associated with their use.

Functional projection: how fundamental social motives can bias interpersonal perception.

Results from 2 experimental studies suggest that self-protection and mate-search goals lead to the perception of functionally relevant emotional expressions in goal-relevant social targets. Activating a self-protection goal led participants to perceive greater anger in Black male faces (Study 1) and Arab faces (Study 2), both out-groups heuristically associated with physical threat. In Study 2, participants' level of implicit Arab-threat associations moderated this bias. Activating a mate-search goal led male, but not female, participants to perceive more sexual arousal in attractive opposite-sex targets (Study 1). Activating these goals did not influence perceptions of goal-irrelevant targets. Additionally, participants with chronic self-protective and mate-search goals exhibited similar biases. Findings are consistent with a functionalist, motivation-based account of interpersonal perception.