What is the function of disgust? Whereas traditional models have suggested that disgust serves to protect the self or neutralize reminders of our animal nature, an evolutionary perspective suggests that disgust functions to solve 3 qualitatively different adaptive problems related to pathogen avoidance, mate choice, and social interaction. The authors investigated this 3-domain model of disgust across 4 studies and examined how sensitivity to these functional domains relates to individual differences in other psychological constructs. Consistent with their predictions, factor analyses demonstrated that disgust sensitivity partitions into domains related to pathogens, sexuality, and morality. Further, sensitivity to the 3 domains showed predictable differentiation based on sex, perceived vulnerability to disease, psychopathic tendencies, and Big 5 personality traits. In exploring these 3 domains of disgust, the authors introduce a new measure of disgust sensitivity. Appreciation of the functional heterogeneity of disgust has important implications for research on individual differences in disgust sensitivity, emotion, clinical impairments, and neuroscience.

Interest in and research on disgust has surged over the past few decades. The field, however, still lacks a coherent theoretical framework for understanding the evolved function or functions of disgust. Here we present such a framework, emphasizing 2 levels of analysis: that of evolved function and that of information processing. Although there is widespread agreement that disgust evolved to motivate the avoidance of contact with disease-causing organisms, there is no consensus about the functions disgust serves when evoked by acts unrelated to pathogen avoidance. Here we suggest that in addition to motivating pathogen avoidance, disgust evolved to regulate decisions in the domains of mate choice and morality. For each proposed evolved function, we posit distinct information processing systems that integrate function-relevant information and account for the trade-offs required of each disgust system. By refocusing the discussion of disgust on computational mechanisms, we recast prior theorizing on disgust into a framework that can generate new lines of empirical and theoretical inquiry.

Evolved mechanisms for assessing genetic relatedness have been found in many species, but their existence in humans has been a matter of controversy. Here we report three converging lines of evidence, drawn from siblings, that support the hypothesis that kin detection mechanisms exist in humans. These operate by computing, for each familiar individual, a unitary regulatory variable (the kinship index) that corresponds to a pairwise estimate of genetic relatedness between self and other. The cues that the system uses were identified by quantitatively matching individual exposure to potential cues of relatedness to variation in three outputs relevant to the system's evolved functions: sibling altruism, aversion to personally engaging in sibling incest, and moral opposition to third party sibling incest. As predicted, the kin detection system uses two distinct, ancestrally valid cues to compute relatedness: the familiar other's perinatal association with the individual's biological mother, and duration of sibling coresidence.For the past 50 years, evolutionary biologists have argued that genetic relatedness should have played a role in the social evolution of species, such as humans, in which close genetic relatives frequently interact 1,2 . According to kin selection theory, computational variants that allocate altruistic effort effectively with respect to kinship out-compete variants that fail to regulate behaviour conditionally in response to relatedness. The effects of relatedness have been documented in a great diversity of taxa, ranging from social amoebas 3 , social insects 4-6 and shrimp 7 , to birds 8 , aphids 9 , plants 10,11 , rodents 12 and primates [13][14][15] . To regulate behaviour conditionally in response to different degrees of kinship, organisms require mechanisms to discriminate genetic relatedness. Such mechanisms have been discovered in a variety of nonhuman species [16][17][18] .Equally, in long-lived, low-fecundity species with an open breeding structure (such as humans), the fitness of offspring is strongly affected by how closely parents are related. In such species, conceptive sexual behaviour between close genetic relatives produces offspring that suffer from inbreeding depression-a decline in fitness caused by rendering more deleterious recessives homozygous [19][20][21] , and aggravated by parasites targeting more genetically homogeneous sets of hosts 22,23 . Consequently, heritable variants that costeffectively reduce inbreeding depression by avoiding mating with close genetic relatives outcompete variants in which mating decisions are unaffected by relatedness.

Packy & Marlon, an interactive video game designed to improve self-care among children and adolescents with diabetes, was evaluated in a six-month randomized controlled trial. In the game, players take the role of animated characters who manage their diabetes by monitoring blood glucose, taking insulin injections, and choosing foods, while setting out to save a diabetes summer camp from marauding rats and mice who have stolen the diabetes supplies. Study participants were patients aged 8 to 16 from two separate diabetes clinics. Each participant received a Super Nintendo video game system at an initial clinic visit and was randomly assigned to receive either Packy & Marlon (treatment group, N = 31) or an entertainment video game containing no diabetes-related content (control group, N = 28). Participants were interviewed and a parent filled out a questionnaire at baseline, three months, and six months. The findings in this study indicate that well-designed, educational video games can be effective interventions. There was improvement in the treatment group relative to the control group in terms of diabetes-related self-efficacy (p = 0.07), communication with parents about diabetes (p = 0.025), and self-care behaviours (p = 0.003), and a decrease in unscheduled urgent doctor visits (p = 0.08). There were no significant differences between the groups in knowledge about diabetes or in glycated haemoglobin (HbA1c) levels. Since participants in the study were in general well-controlled patients who were receiving excellent medical care, future research is contemplated involving youngsters who are not under good glycaemic control.