The nematode worm C. elegans chooses between bacterial foods as if maximizing economic utility.

In value-based decision making, options are selected according to subjective values assigned by the individual to available goods and actions. Despite the importance of this faculty of the mind, the neural mechanisms of value assignments, and how choices are directed by them, remain obscure. To investigate this problem, we used a classic measure of utility maximization, the Generalized Axiom of Revealed Preference, to quantify internal consistency of food preferences in Caenorhabditis elegans, a nematode worm with a nervous system of only 302 neurons. Using a novel combination of microfluidics and electrophysiology, we found that C. elegans food choices fulfill the necessary and sufficient conditions for utility maximization, indicating that nematodes behave as if they maintain, and attempt to maximize, an underlying representation of subjective value. Food choices are well-fit by a utility function widely used to model human consumers. Moreover, as in many other animals, subjective values in C. elegans are learned, a process we find requires intact dopamine signaling. Differential responses of identified chemosensory neurons to foods with distinct growth potentials are amplified by prior consumption of these foods, suggesting that these neurons may be part of a value-assignment system. The demonstration of utility maximization in an organism with a very small nervous system sets a new lower bound on the computational requirements for utility maximization and offers the prospect of an essentially complete explanation of value-based decision making at single neuron resolution in this organism.

The causal effect of testosterone on men's competitive behavior is moderated by basal cortisol and cues to an opponent's status: Evidence for a context-dependent dual-hormone hypothesis.

Testosterone has been theorized to direct status-seeking behaviors, including competitive behavior. However, most human studies to date have adopted correlational designs, and findings across studies are inconsistent. This experiment (n = 115) pharmacologically manipulated men's testosterone levels prior to a mixed-gender math competition and examined basal cortisol (a hormone implicated in stress and social avoidance) and context cues related to an opponent's perceived status (an opponent's gender or a win/loss in a prior competition) as factors that may moderate testosterone's impact on competitive behavior. We test and find support for the hypothesis that testosterone given to low-cortisol men evokes status-seeking behavior, whereas testosterone given to high-cortisol men evokes status-loss avoidance. In the initial rounds of competition, testosterone's influence on competitive decisions depended on basal cortisol and opponent gender. After providing opponent-specific win-lose feedback, testosterone's influence on decisions to reenter competitions depended on basal cortisol and this objective cue to status, not gender. Compared to placebo, men given exogenous testosterone who were low in basal cortisol showed an increased tendency to compete against male and high-status opponents relative to female and low-status opponents (status-seeking). Men given exogenous testosterone who were high in basal cortisol showed the opposite pattern-an increased tendency to compete against female and low-status opponents relative to male and high-status opponents (status-loss avoidance). These results provide support for a context-dependent dual-hormone hypothesis: Testosterone flexibly directs men's competitive behavior contingent on basal cortisol levels and cues that signal an opponent's status. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Exogenous testosterone enhances cortisol and affective responses to social-evaluative stress in dominant men.

Stress often precedes the onset of mental health disorders and is linked to negative impacts on physical health as well. Prior research indicates that testosterone levels are related to reduced stress reactivity in some cases but correlate with increased stress responses in other cases. To resolve these inconsistencies, we tested the causal influence of testosterone on stress reactivity to a social-evaluative stressor. Further, prior work has failed to consider status-relevant individual differences such as trait dominance that may modulate the influence of testosterone on responses to stressors. Participants (n=120 males) were randomly assigned to receive exogenous testosterone or placebo (n=60 testosterone treatment group) via topical gel prior to a well-validated social-evaluative stressor. Compared to placebo, testosterone significantly increased cortisol and negative affect in response to the stressor, especially for men high in trait dominance (95% confidence intervals did not contain zero). The findings suggest that the combination of high testosterone and exposure to status-relevant social stress may confer increased risk for stress-mediated disorders, particularly for individuals high in trait dominance.

A general benevolence dimension that links neural, psychological, economic, and life-span data on altruistic tendencies.

[Correction Notice: An Erratum for this article was reported in Vol 145(10) of Journal of Experimental Psychology: General (see record 2016-46925-004). In the article, there was an error in the Task, Stimuli, and Procedures section. In the 1st sentence in the 6th paragraph, "Following the scanning phase, participants completed self-report questionnaires meant to reflected the Prosocial Disposition construct: the agreeableness scale from the Big F, which includes empathic concern and perspective-taking, and a scale of personality descriptive adjectives related to altruistic behavior (Wood, Nye, & Saucier, 2010)." should have read: "Following the scanning phase, participants completed self-report questionnaires that contained scales to reflect the Prosocial Disposition construct: the Big Five Inventory (BFI; John et al., 1991), from which we used the agreeableness scale to measure prosocial disposition; the Interpersonal Reactivity Index (IRI; Davis, 1980), from which we used the empathic concern and perspective-taking scales; and a scale of personality descriptive adjectives related to altruistic behavior (Wood, Nye, & Saucier, 2010)."] Individual and life span differences in charitable giving are an important economic force, yet the underlying motives are not well understood. In an adult, life span sample, we assessed manifestations of prosocial tendencies across 3 different measurement domains: (a) psychological self-report measures, (b) actual giving choices, and (c) fMRI-derived, neural indicators of "pure altruism." The latter expressed individuals' activity in neural valuation areas when charities received money compared to when oneself received money and thus reflected an altruistic concern for others. Results based both on structural equation modeling and unit-weighted aggregate scores revealed a strong higher-order General Benevolence dimension that accounted for variability across all measurement domains. The fact that the neural measures likely reflect pure altruistic tendencies indicates that General Benevolence is based on a genuine concern for others. Furthermore, General Benevolence exhibited a robust increase across the adult life span, potentially providing an explanation for why older adults typically contribute more to the public good than young adults.

Competitiveness across the life span: the feisty fifties.

Existing theories on life span changes in confidence or motivation suggest that individuals' preferences to enter competitive situations should gradually decline with age. We examined competitive preferences in a field experiment using real financial stakes in 25- to 75-year-olds (N = 543). The critical dependent variable was whether participants chose to perform a simple mental arithmetic task either under a piece-rate payment schedule (i.e., $.25 per solved item) or a competitive payment schedule ($.50 per solved item if the overall score is better than that of a randomly selected opponent, $0 otherwise). Results revealed that competitive preferences increased across the life span until they peaked around age 50, and dropped thereafter. We also found that throughout, men had a substantially larger preference for competing than women-extending previous findings on college-aged participants. The age/gender differences in preferences were neither accounted for by actual differences in performance nor individuals' subjective confidence. This first systematic attempt to characterize age differences in competitive behavior suggests that a simple decline conception of competitiveness needs to be reconsidered.

Risk, reward, and economic decision making in aging.

OBJECTIVES: Older adults' decision quality is considered to be worse than that of younger adults. This age-related difference is often attributed to reductions in risk tolerance. Little is known about the circumstances that affect older adults' decisions and whether risk attitudes directly influence economic decisions. We measure the influence of risk attitudes on age-related differences in decision making in both nonsocial and social contexts. METHODS: Risk attitudes and economic decision making were measured in 30 healthy older adults and 29 healthy younger adults. RESULTS: Older adults report being less impulsive, sensation seeking and risk tolerant than younger adults. Age did not affect a measure of nonsocial economic decision making. Older adults were more likely to reject unfair divisions of money during an economic social-bargaining game and more likely to make equitable divisions of money during social-giving game. These age-related differences were determined in part by individuals' self-reported risk taking. DISCUSSION: We conclude that age-related differences in decision making are domain specific and that some social economic decision making is influenced by risk attitudes. Older adults are more risk avoidant, but this does not alter their willingness to wait for reward in a nonsocial context. Perceiving more risk is associated with an unwillingness to accept an unfair offer in social economic contexts and ultimately leads to poorer outcomes for older adults.

Neural responses to taxation and voluntary giving reveal motives for charitable donations.

Civil societies function because people pay taxes and make charitable contributions to provide public goods. One possible motive for charitable contributions, called "pure altruism," is satisfied by increases in the public good no matter the source or intent. Another possible motive, "warm glow," is only fulfilled by an individual's own voluntary donations. Consistent with pure altruism, we find that even mandatory, tax-like transfers to a charity elicit neural activity in areas linked to reward processing. Moreover, neural responses to the charity's financial gains predict voluntary giving. However, consistent with warm glow, neural activity further increases when people make transfers voluntarily. Both pure altruism and warm-glow motives appear to determine the hedonic consequences of financial transfers to the public good.