Parasite-stress promotes in-group assortative sociality: the cases of strong family ties and heightened religiosity

Throughout the world people differ in the magnitude with which they value strong family ties or heightened religiosity. We propose that this cross-cultural variation is a result of a contingent psychological adaptation that facilitates in-group assortative sociality in the face of high levels of parasite-stress while devaluing in-group assortative sociality in areas with low levels of parasite-stress. This is because in-group assortative sociality is more important for the avoidance of infection from novel parasites and for the management of infection in regions with high levels of parasite-stress compared with regions of low infectious disease stress. We examined this hypothesis by testing the predictions that there would be a positive association between parasite-stress and strength of family ties or religiosity. We conducted this study by comparing among nations and among states in the United States of America. We found for both the international and the interstate analyses that in-group assortative sociality was positively associated with parasite-stress. This was true when controlling for potentially confounding factors such as human freedom and economic development. The findings support the parasite-stress theory of sociality, that is, the proposal that parasite-stress is central to the evolution of social life in humans and other animals.     

Parasite prevalence and the distribution of intelligence among the states of the USA

In this study, we tested the parasite-stress hypothesis for the distribution of intelligence among the USA states: the hypothesis proposes that intelligence emerges from a developmental trade-off between maximizing brain vs. immune function. From this we predicted that among the USA states where infectious disease stress was high, average intelligence would be low and where infectious disease stress was low, average intelligence would be high. As predicted, we found that the correlation between average state IQ and infectious disease stress was ? 0.67 (p < 0.0001) across the 50 states. Furthermore, when controlling the effects of wealth and educational variation among states, infectious disease stress was the best predictor of average state IQ.     

Rethinking innovative designs to further test parasite-stress theory

Fincher & Thornhill's (F&T's) parasite-stress theory of sociality is supported largely by correlational evidence; its persuasiveness would increase significantly via lab and natural experiments and demonstrations of its mediating role. How the theory is linked to other approaches to group differences in psychological differences and to production and dissemination of cultural ideas and practices, need further clarification. So does the theory's view on the possible reduction of negative group interactions.     

Zoonotic and non-zoonotic diseases in relation to human personality and societal values: Support for the parasite-stress model

The parasite-stress model of human sociality proposes that humans' ontogenetic experiences with infectious diseases as well as their evolutionary historical interactions with these diseases exert causal influences on human psychology and social behavior. This model has been supported by cross-national relationships between parasite prevalence and human personality traits, and between parasite prevalence and societal values. Importantly, the parasite-stress model emphasizes the causal role of non-zoonotic parasites (which have the capacity for human-to-human transmission), rather than zoonotic parasites (which do not), but previous studies failed to distinguish between these conceptually distinct cate- gories. The present investigation directly tested the differential predictive effects of zoonotic and non-zoonotic (both human-specific and multihost) parasite prevalence on personality traits and societal values. Supporting the parasite-stress model, cross-national differences in personality traits (unrestricted sexuality, extraversion, openness to experi- ences) and in societal values (individualism, collectivism, gender equality, democratiza- tion) are predicted specifically by non-zoonotic parasite prevalence.     

The evolution and development of human social systems requires more than parasite-stress avoidance explanation

Fincher & Thornhill (F&T) present a model of in-group assortative sociality resulting from differing levels of parasite-stress in differing geographical locations in the United States and the world. Their model, while compelling, overlooks some important issues, such as mutualistic associations with parasites that are beneficial to humans and how some religious practices increase parasite risk.     

Analyses do not support the parasite-stress theory of human sociality

Re-analysis of the data provided in the target article reveals a lack of evidence for a strong, universal relationship between parasite stress and the variables relating to sociality. Furthermore, even if associations between these variables do exist, the analyses presented here do not provide evidence for Fincher & Thornhill's (F&T's) proposed causal mechanism.     

Time allocation, religious observance, and illness in Mayan horticulturalists

Analysis of individual differences in religious observance in a Belizean community showed that the most religious (pastors and church workers) reported more illnesses, and that there was no tendency for the religiously observant to restrict their interactions to family or extended family. Instead, the most religiously observant tended to have community roles that widened their social contact: religion did not aid isolation - thus violating a key assumption of the parasite-stress theory of sociality.     

Extending parasite-stress theory to variation in human mate preferences

In this commentary we suggest that Fincher & Thornhill's (F&T's) parasite-stress theory of social behaviors and attitudes can be extended to mating behaviors and preferences. We discuss evidence from prior correlational and experimental studies that support this claim. We also reanalyze data from two of those studies using F&T's new parasite stress measures.     

Attentional control and reflexive orienting to gaze and arrow cues

A wealth of data indicate that central spatially nonpredictive eyes and arrows trigger very similar reflexive spatial orienting, although the effects of eyes may be more strongly reflexive (e.g., Friesen, Ristic, & Kingstone, 2004). Pratt and Hommel (2003) recently reported that the orienting effect for arrows is sensitive to arbitrary cue-target color contingencies; for example, an attentional orienting effect for blue colored arrows is evident only for blue targets. We reasoned that if the orienting effect elicited by eye direction is more strongly reflexive than the orienting effect elicited by arrow direction, it follows that eyes, unlike arrows, may trigger orienting effects that generalize across congruent and incongruent cue-target color contingencies. Replicating Pratt and Hommel (2003), we found that the reflexive attention effect elicited by arrows is specific to color-congruent target stimuli. The attention effect triggered by eyes, however, generalizes across color-congruent and color-incongruent target stimuli. These data support the hypothesis that eye direction and arrow direction trigger similar reflexive shifts in spatial attention, but that the attention effect triggered by eye direction is more strongly reflexive.     

Linking Genes and Political Orientations: Testing the Cognitive Ability as Mediator Hypothesis

Recent research has demonstrated that genetic differences explain a sizeable fraction of the variance in political orientations, but little is known about the pathways through which genes might affect political preferences. In this article, we use a uniquely assembled dataset of almost 1,000 Swedish male twin pairs containing detailed information on cognitive ability and political attitudes in order to further examine the genetic and environmental causes of political orientations. Our study makes three distinct contributions to our understanding of the etiology of political orientations: (1) we report heritability estimates across different dimensions of political ideology; (2) we show that cognitive ability and political orientations are related; and (3) we provide evidence consistent with the hypothesis that cognitive ability mediates part of the genetic influence on political orientations. These findings provide important clues about the nature of the complex pathways from molecular genetic variation to political orientations.     

Age effects may be global, not local: comment on Fisk and Rogers (1991)

A series of analyses of variance on target search times allowed Fisk and Rogers (1991) to reject the null hypothesis that age had a uniform, additive effect across search conditions. It does not, however, follow that age affected some conditions in an exceptional way, as Fisk and Rogers concluded. Age may have had a uniform but nonadditive effect across conditions. In this article, it is shown that age had a uniform linear, or perhaps slightly curvilinear, effect on search times. This "null hypothesis" adequately accounted for the age effects in all 27 search conditions. Indeed, it accounted for the age effects in 107 conditions abstracted from other visual search studied and for the age effects in 154 conditions abstracted from a miscellaneous collection of nonsearch processing-time studies. The only variation in age outcomes across studies was consistent with sampling error, given the known variance in response times. It is concluded that age is experienced as a generalized slowing of the central nervous system uniformly affecting all information processes.     

An ethical and prudential argument for prioritizing the reduction of parasite-stress in the allocation of health care resources

The link between parasite-stress and complex psychological dispositions implies that the social, political, and economic benefits likely to flow from public health interventions that reduce rates of non-zoonotic infectious disease are far greater than have traditionally been thought. We sketch a prudential and ethical argument for increasing public health resources globally and redistributing these to focus on the alleviation of parasite-stress in human populations.     

Immigration, parasitic infection, and United States religiosity

Fincher & Thornhill (F&T) present a powerful case for the relationship between parasite-stress and religiosity. We argue, however, that the United States may be more religious than can be accounted for by parasite-stress. This greater religiosity might be attributable to greater sensitivity to immigration, which may hyperactivate evolved mechanisms that motivate avoidance of potential carriers of novel parasites.     

Young children''s naive theory of biology

This article aimed at investigating the nature of young children's naive theory of biology by reviewing a large number of studies conducted in our laboratories. More specifically, we tried to answer the following five critical questions. What components does young children's knowledge system for biological phenomena (or naive biology) have? What functions does it have in children's lives? How is it acquired in ontogenesis? How does its early version change as children grow older? Is it universal across cultures and through history? We propose that young children's biological knowledge system has at least three components, that is, knowledge needed to specify the target objects of biology, ways of inferring attributes or behaviors of biological kinds, and a non-intentional causal explanatory framework, and that these three constitute a form of biology, which is adaptive in children's lives. We also claim that the core of naive biology is acquired based on specific cognitive constraints as well as the general mechanism of personification and the resultant vitalistic causality, but it is differently instantiated and elaborated through activity-based experiences in the surrounding culture.     

Cross-cultural perspectives: implications for attachment theory and family therapy

Cross-cultural perspectives have always been useful for understanding behavior. They clarify the distinction between aspects that are essentially part of the human condition and those that are the most responsive to variation. The interesting article by Rothbaum and his colleagues is in that tradition, contrasting the cultural values and family patterns in Japanese society with those of Western cultures, including our own, and suggesting that these differences shape the nature and course of attachment. It stimulates questions about what we have taken for granted in our theories and in our evaluations of dysfunctional behavior.     

Formalising a hypothesis for the development of anticipatory skill in time-constrained interceptive actions: Implications for the design of junior sport

When professional athletes strike a ball in tennis, cricket or baseball, the high temporal demands often necessitate the need to exploit pre-ball-flight information in order to anticipate the ball's trajectory. Despite the wealth of research probing anticipatory behaviour in sport, our understanding of when, how or why anticipatory skill develops is limited. In this article, we sought to formalise a hypothesis on the development of anticipatory skill. Using empirical temporal data from tennis, cricket and baseball, we propose that the temporal demands of the task dictate an athlete's propensity to anticipate. We then outline the implications of this hypothesis as it relates to junior sport. Notably, we question whether current playing dimensions in junior sport impose temporal demands that are sufficient to elicit anticipatory behaviour. Using tennis, cricket and baseball as examples, we illustrate differences in temporal demands between the junior and professional game and present implications for anticipation. Our discussion challenges the current junior sport experience as it relates to developing anticipatory skill.     

Fraisse's theory of emotion and aggression.

This article shows how Fraisse's (1964) theory of emotion is a better explanation of aggression than any other theory of emotion. It discusses conceptual and methodological difficulties in existing theories of aggression and reports a study that supports a hypothesis based on Fraisse's theory. This study, which used Canadian university students equally divided by sex, supports the hypothesis that subjects would be more aggressive when faced with an unexpected annoyance than with an expected annoyance. Aggression was indexed by subjects' evaluation of the target person (confederate) as a source of annoyance.     

Buffering against weight gain following dieting setbacks: An implicit theory intervention

Research on implicit theories suggests that incremental beliefs—that attributes are malleable—can help buffer people against the adverse effects of setbacks on goal achievement. We conducted a longitudinal experiment to examine whether an incremental beliefs intervention could help dieters manage their body weight in the face of severe dieting setbacks. To explore the efficacy of our incremental beliefs intervention, we randomly assigned individuals to a control, a knowledge, or an incremental beliefs condition. In addition to examining the main effect of intervention condition on weight-loss across a 12-week period, we also tested the hypothesis that although participants assigned to the control or knowledge intervention condition would gain more weight as dieting setbacks became more severe, participants assigned to the incremental beliefs condition would not. Results supported this hypothesis: Incremental beliefs protected against setback-related weight-gain. Implications for integrating implicit beliefs interventions with obesity relapse prevention programs are discussed.     

‘The system is unfair’: Uncontrollable attributions for inequality predict more equitable giving in adolescents

Socioeconomic position is often determined by uncontrollable, structural factors, yet people from the United States tend to attribute wealth and poverty to individual control. However, information about behavioural correlates of such beliefs across development is relatively lacking. Thus, we examined adolescents' reasoning about the causes of inequality in a sample of 599 adolescents from a socioeconomically, ethnically, and racially diverse middle school (grades 6–8). Additionally, early adolescents were presented with two novel groups with an unexplained wealth disparity and given a task in which they could perpetuate or rectify inequality. We found that while adolescents tended to give equitably and rectify the inequality, this outcome was predicted by the type of explanation they gave for societal inequality. Furthermore, participants' socioeconomic status and sexual identity predicted their inequality explanations. These results add to our knowledge of adolescent reasoning about inequality by demonstrating a potential link between attributions for inequality and giving behaviour.