Robert O. Deaner

Mirroring of attention by neurons in macaque parietal cortex

Macaques, like humans, rapidly orient their attention in the direction other individuals are looking. Both cortical and subcortical pathways have been proposed as neural mediators of social gaze following, but neither pathway has been characterized electrophysiologically in behaving animals. To address this gap, we recorded the activity of single neurons in the lateral intraparietal area (LIP) of rhesus macaques to determine whether and how this area might contribute to gaze following. A subset of LIP neurons mirrored observed attention by firing both when the subject looked in the preferred direction of the neuron, and when observed monkeys looked in the preferred direction of the neuron, despite the irrelevance of the monkey images to the task. Importantly, the timing of these modulations matched the time course of gaze-following behavior. A second population of neurons was suppressed by social gaze cues, possibly subserving task demands by maintaining fixation on the observed face. These observations suggest that LIP contributes to sharing of observed attention and link mirror representations in parietal cortex to a well studied imitative behavior.

Economic principles motivating social attention in humans

We know little about the processes by which we evaluate the opportunity to look at another person. We propose that behavioural economics provides a powerful approach to understanding this basic aspect of social attention. We hypothesized that the decision process culminating in attention to another person follows the same economic principles that govern choices about rewards such as food, drinks and money. Specifically, such rewards are discounted as a function of time, are tradable for other rewards, and reinforce work. Behavioural and neurobiological evidence suggests that looking at other people can also be described as rewarding, but to what extent these economic principles apply to social orienting remains unknown. Here, we show that the opportunity to view pictures of the opposite sex is discounted by delay to viewing, substitutes for money and reinforces work. The reward value of photos of the opposite sex varied with physical attractiveness and was greater in men, suggesting differential utility of acquiring visual information about the opposite sex in men and women. Together, these results demonstrate that choosing whom to look at follows a general set of economic principles, implicating shared neural mechanisms in both social and non-social decision making.

Neural correlates of social target value in macaque parietal cortex.

Animals as diverse as arthropods [1], fish [2], reptiles [3], birds [4], and mammals, including primates [5], depend on visually acquired information about conspecifics for survival and reproduction. For example, mate localization often relies on vision [6], and visual cues frequently advertise sexual receptivity or phenotypic quality [5]. Moreover, recognizing previously encountered competitors or individuals with preestablished territories [7] or dominance status [1, 5] can eliminate the need for confrontation and the associated energetic expense and risk for injury. Furthermore, primates, including humans, tend to look toward conspecifics and objects of their attention [8, 9], and male monkeys will forego juice rewards to view images of high-ranking males and female genitalia [10]. Despite these observations, we know little about how the brain evaluates social information or uses this appraisal to guide behavior. Here, we show that neurons in the primate lateral intraparietal area (LIP), a cortical area previously linked to attention and saccade planning [11, 12], signal the value of social information when this assessment influences orienting decisions. In contrast, social expectations had no impact on LIP neuron activity when monkeys were not required to make a choice. These results demonstrate for the first time that parietal cortex carries abstract, modality-independent target value signals that inform the choice of where to look.

A sex difference in the predisposition for physical competition: males play sports much more than females even in the contemporary U.S.

Much evidence indicates that men experienced an evolutionary history of physical competition, both one-on-one and in coalitions. We thus hypothesized that, compared to girls and women, boys and men will possess a greater motivational predisposition to be interested in sports, especially team sports. According to most scholars, advocacy groups, and the United States courts, however, this hypothesis is challenged by modest sex differences in organized school sports participation in the contemporary U.S., where females comprise 42% of high school participants and 43% of intercollegiate participants. We conducted three studies to test whether organized school sports participation data underestimate the actual sex difference in sports participation. Study 1 analyzed the American Time Use Survey, which interviewed 112,000 individuals regarding their activities during one day. Females accounted for 51% of exercise (i.e., non-competitive) participations, 24% of total sports participations, and 20% of team sports participations. These sex differences were similar for older and younger age groups. Study 2 was based on systematic observations of sports and exercise at 41 public parks in four states. Females accounted for 37% of exercise participations, 19% of individual sports participations, and 10% of team sports participations. Study 3 involved surveying colleges and universities about intramural sports, which primarily consist of undergraduate participation in team sports. Across 34 institutions, females accounted for 26% of registrations. Nine institutions provided historical data, and these did not indicate that the sex difference is diminishing. Therefore, although efforts to ensure more equitable access to sports in the U.S. (i.e., Title IX) have produced many benefits, patterns of sports participation do not challenge the hypothesis of a large sex difference in interest and participation in physical competition.

Distance Running as an Ideal Domain for Showing a Sex Difference in Competitiveness

Men are over-represented in the arts, sciences, and sports. This has been hypothesized to reflect an evolved male predisposition for enduring competitiveness or long-term motivation to improve one’s performance and “show-off.” Evidence for this hypothesis is equivocal, however, because there are viable alternative explanations for men’s dominance in most cultural display domains. Here, I argue that distance running is an ideal domain for addressing this issue. Distance running is ideal because it indicates enduring competitiveness, allows objective comparisons, and is accessible, acceptable, and popular for both men and women. I review recent studies and present new data showing that substantially more men than women run relatively fast in the U.S., that this sex difference in relative performance can be attributed, at least in part, to men’s greater training motivation, and that this pattern has been stable for several decades. Distance running thus provides compelling evidence for an evolved male predisposition for enduring competitiveness. I conclude with suggestions regarding how variation in achievement motivation can be informed by considering how evolved predispositions interact with environmental and social conditions.

The Evolutionary Significance of Red Sox Nation: Sport Fandom as a Byproduct of Coalitional Psychology

Sport fandom has received considerable attention from social scientists, yet few have considered it from an evolutionary perspective. To redress this gap, we develop the hypothesis that team sports exhibit characteristics that activate mechanisms which evolved to facilitate the development of coalitions in the context of small-scale warfare. Based on this by-product hypothesis, we predicted a correlation between fandom and binding (i.e. group-relevant) concerns, especially loyalty. To test this prediction, we administered the Sport Spectator Identification Scale (SSI) and the Moral Foundations Questionnaire (MFQ) to 495 undergraduates. The MFQ measures three binding concerns, including loyalty, and two individualizing ones, harm and fairness. As predicted, fandom correlated significantly with loyalty (r = .27) and, within men, the two other binding concerns, authority (r =.22) and purity (r = .24). By contrast, fandom did not significantly correlate with harm or fairness. In addition, we predicted and found that men reported significantly higher levels of fandom (Cohens d =.45) and loyalty (d = .27) than did women. In conclusion, this study presents data supporting the coalitional by-product hypothesis of fandom and should spur further research using fandom as a window into our evolved psychology.

Sex Differences in Sports Across 50 Societies

Sports have been frequently explored in cross-cultural studies, yet scant attention has been paid to female participation. Here we coded the occurrence of sports and related activities for males and females in the societies comprising the Human Relations Area Files (HRAF) probability sample. We then tested several predictions derived from evolutionary theory. As predicted, in all 50 societies with documented sports, there were more male sports than female sports; hunting and combat sports were almost exclusively male activities; and the sex difference in sports was greater in patriarchal than in nonpatriarchal societies. These results show that a robust sex difference in direct physical competition co-occurs with meaningful variation in its expression.

Born at the wrong time: selection bias in the NHL draft.

Relative age effects (RAEs) occur when those who are relatively older for their age group are more likely to succeed. RAEs occur reliably in some educational and athletic contexts, yet the causal mechanisms remain unclear. Here we provide the first direct test of one mechanism, selection bias, which can be defined as evaluators granting fewer opportunities to relatively younger individuals than is warranted by their latent ability. Because RAEs are well-established in hockey, we analyzed National Hockey League (NHL) drafts from 1980 to 2006. Compared to those born in the first quarter (i.e., January–March), those born in the third and fourth quarters were drafted more than 40 slots later than their productivity warranted, and they were roughly twice as likely to reach career benchmarks, such as 400 games played or 200 points scored. This selection bias in drafting did not decrease over time, apparently continues to occur, and reduces the playing opportunities of relatively younger players. This bias is remarkable because it is exhibited by professional decision makers evaluating adults in a context where RAEs have been widely publicized. Thus, selection bias based on relative age may be pervasive.

More Men Run Relatively Fast in U.S. Road Races, 1981–2006: A Stable Sex Difference in Non-Elite Runners

Recent studies indicate that more men than women run fast relative to sex-specific world records and that this sex difference has been historically stable in elite U.S. runners. These findings have been hypothesized to reflect an evolved male predisposition for enduring competitiveness in “show-off” domains. The current study tests this hypothesis in non-elite runners by analyzing 342 road races that occurred from 1981–2006, most in or near Buffalo, NY. Both absolutely and as a percentage of same-sex finishers, more men ran relatively fast in most races. During the 1980s, as female participation surged, the difference in the absolute number of relatively fast men and women decreased. However, this difference was stable for races that occurred after 1993. Since then, in any given race, about three to four times as many men as women ran relatively fast. The stable sex difference in relative performance shown here for non-elites constitutes new support for the hypothesis of an evolved male predisposition for enduring competitiveness.

More Males Run Relatively Fast in U.S. Road Races: Further Evidence of a Sex Difference in Competitiveness

Deaner (2006) recently showed that among elite U.S. runners, two to four times as many males as females run fast relative to sex-specific world-class standards. Previous questionnaire studies of non-elite runners suggest this phenomenon may reflect a sex difference in motivation to train competitively. If this hypothesis is correct, then the sex difference in performance depth should also hold in non-elite running populations. Here I tested this prediction by analyzing the finishing times at 20 of the largest 5000 m road races and 20 of the largest marathons held in the U.S. in 2003. For both types of races, overall population distributions of relative performance were similar in males and females. However, at the fastest relative performance levels, males were over represented by two to four times. This difference could not be explained by the presence of professional runners or as an artifact of biased world-class standards. This result shows that the sex difference in performance depth occurs generally and thus supports the hypothesis that sex differences in competitiveness partly reflect evolved predispositions.