Daniel Brian Krupp

Looking for Ms. Right: Allocating Attention to Facilitate Mate Choice Decisions

Through various signals, the human body provides information that may be used by receivers to make decisions about mate value. Here, we investigate whether there exists a complementary psychological system designed to selectively attend to these signals in order to choose, and direct effort toward the acquisition of, a potential mate. We presented young men with three images of the same woman (six women in total) simultaneously, varying the waist-to-hip ratio (WHR) of each image while holding other traits constant. While participants chose their preferred image, we monitored visual attention using an infrared eye-tracker. We found that participants focused their attention selectively on body regions known to provide reproductive information in a manner consistent with the research hypothesis: Reproductively relevant body regions, especially the head and breasts, received the most visual attention. Likewise, images with lower WHRs and reproductively relevant regions in images with lower WHRs received the most visual attention and were chosen as most attractive. Finally, irrespective of WHR size, participants fixated more often and for longer durations on the images that they selected as most attractive.

A Test of Two Typologies of Sexual Homicide

Published typologies of sexual homicide lack theoretical grounding and empirical support. They also conceptualize the phenomenon of sexual homicide as somewhat discrete, though offenders are not typically specialists. Here, we propose a model that situates the phenomenon of sexual killing into broader categories of antisocial behavior, positing three types of perpetrators of serial sexual homicides: competitively disadvantaged, psychopathic, and sadistic offenders. Using biographical data of 82 serial sexual homicide offenders, we tested our model as well as the influential organized/disorganized model. Principal components analysis produced five components consisting of offender and offense characteristics, and cluster analysis revealed three distinct groups of perpetrators (sadistic offenders, competitively disadvantaged offenders, and slashers), as well as a fourth, heterogeneous group; this cluster solution, however, may be unstable. In summary, there is only mixed support for either model.

Nepotistic patterns of violent psychopathy: evidence for adaptation?

Psychopaths routinely disregard social norms by engaging in selfish, antisocial, often violent behavior. Commonly characterized as mentally disordered, recent evidence suggests that psychopaths are executing a well-functioning, if unscrupulous strategy that historically increased reproductive success at the expense of others. Natural selection ought to have favored strategies that spared close kin from harm, however, because actions affecting the fitness of genetic relatives contribute to an individual’s inclusive fitness. Conversely, there is evidence that mental disorders can disrupt psychological mechanisms designed to protect relatives. Thus, mental disorder and adaptation accounts of psychopathy generate opposing hypotheses: psychopathy should be associated with an increase in the victimization of kin in the former account but not in the latter. Contrary to the mental disorder hypothesis, we show here in a sample of 289 violent offenders that variation in psychopathy predicts a decrease in the genetic relatedness of victims to offenders; that is, psychopathy predicts an increased likelihood of harming non-relatives. Because nepotistic inhibition in violence may be caused by dispersal or kin discrimination, we examined the effects of psychopathy on (1) the dispersal of offenders and their kin and (2) sexual assault frequency (as a window on kin discrimination). Although psychopathy was negatively associated with coresidence with kin and positively associated with the commission of sexual assault, it remained negatively associated with the genetic relatedness of victims to offenders after removing cases of offenders who had coresided with kin and cases of sexual assault from the analyses. These results stand in contrast to models positing psychopathy as a pathology, and provide support for the hypothesis that psychopathy reflects an evolutionary strategy largely favoring the exploitation of non-relatives.

Kin recognition: evidence that humans can perceive both positive and negative relatedness

The evolution of spite entails actors imposing costs on ‘negative’ relatives: those who are less likely than chance to share the actor’s alleles and therefore more likely to bear rival alleles. Yet, despite a considerable body of research confirming that organisms can recognize positive relatives, little research has shown that organisms can recognize negative relatives. Here, we extend previous work on human phenotype matching by introducing a cue to negative relatedness: negative self‐resembling faces, which differ from an average face in the opposite direction to the way an individual’s own face differs from the average. Participants made trustworthiness and attractiveness judgements of pairs of opposite‐sex positive and negative self‐resembling faces. Analyses revealed opposing effects of positive and negative self‐resembling faces on trustworthiness and attractiveness judgements. This is the first clear evidence that humans are sensitive to negative relatedness cues, and suggests the potential for the adaptive allocation of spiteful behaviour.

Psychopathy, adaptation, and disorder.

In a recent study, we found a negative association between psychopathy and violence against genetic relatives. We interpreted this result as a form of nepotism and argued that it failed to support the hypothesis that psychopathy is a mental disorder, suggesting instead that it supports the hypothesis that psychopathy is an evolved life history strategy. This interpretation and subsequent arguments have been challenged in a number of ways. Here, we identify several misunderstandings regarding the harmful dysfunction definition of mental disorder as it applies to psychopathy and regarding the meaning of nepotism. Furthermore, we examine the evidence provided by our critics that psychopathy is associated with other disorders, and we offer a comment on their alternative model of psychopathy. We conclude that there remains little evidence that psychopathy is the product of dysfunctional mechanisms.

Marital, Reproductive, and Educational Behaviors Covary with Life Expectancy

Theories of “life history evolution” suggest that individuals might adjust the timing of marriage and reproduction, as well as their propensity to terminate a marriage or pregnancy and invest in skill development, in response to indicators of the locally prevailing level of life expectancy. In particular, such theories generate the hypothesis that foreshortened time horizons lead to hastened reproduction and marriage whereas lengthier time horizons increase the likelihood of reproductive and marital termination and lead to greater investment in education. Here, I show that the scheduling and occurrence of marital and reproductive behavior (including both initiation and termination), as well as levels of educational attainment and investment, covary with life expectancy, even after controlling for the effects of affluence. In analyses of variation in marital, reproductive, and educational behaviors at two jurisdictional levels in Canada, life expectancy was positively correlated with patterns of age-specific fertility, age at first marriage, divorce, abortion, conferral of high school and higher education degrees (with the exception of the trades) and mean number of years of schooling. The large and highly consistent relationships observed between life expectancy and the behaviors under investigation suggest that these associations may be mediated by individual “perceptions” of life expectancy, though more research is needed before conclusions can be firmly reached.

Free Viewing Perceptual Asymmetry for Distance Judgments: Objects in Right Hemispace are Closer than They Appear

Neurologically normal individuals demonstrate leftward biases in tasks of line bisection and judgments of brightness, numerosity, and size. Normals also report and demonstrate a right-sided bias when bumping into objects. Collectively, these results suggest that normals relatively neglect the right hemispace. The present experiment investigated the possibility that normals will also demonstrate leftward biases for judgments of distance. Participants viewed two equivalent but mirror-reversed three-dimensional shapes (“boxes” and “pyramids”) of various orientations, sizes, and angles, making judgments about the perceived closeness of the stimuli. Significant leftward biases were exhibited for judgments of the closeness of boxes, but not for pyramids. The findings of the current study support the hypothesis that the normal tendency to bump into objects with the right side of ones body might be due to a perceptual asymmetry for distance judgments.

Enhanced Kin Recognition through Population Estimation

Kin recognition systems enable organisms to predict genetic relatedness. In so doing, they help to maximize the fitness consequences of social actions. Recognition based on phenotypic similarity—a process known as phenotype matching—is thought to depend upon information about one’s own phenotype and the phenotypes of one’s partners. We provide a simple model of genetic relatedness conditioned upon phenotypic information, however, that demonstrates that individuals additionally require estimates of the distributions of phenotypes and genotypes in the population. Following the results of our model, we develop an expanded concept of phenotype matching that brings relatedness judgments closer in line with relatedness as it is currently understood and provides a heuristic mechanism by which individuals can discriminate positive from negative relatives, thereby increasing opportunities for the evolution of altruism and spite. Finally, we propose ways in which organisms might acquire population estimates and identify research that supports their use in phenotype matching.

How to distinguish altruism from spite (and why we should bother)

Social behaviour is often described as altruistic, spiteful, selfish or mutually beneficial. These terms are appealing, but it has not always been clear how they are defined and what purpose they serve. Here, I show that the distinctions among them arise from the ways in which fitness is partitioned: none can be drawn when the fitness consequences of an action are wholly aggregated, but they manifest clearly when the consequences are partitioned into primary and secondary (neighbourhood) effects. I argue that the primary interaction is the principal source of adaptive design, because (i) it is this interaction that determines the fit of an adaptation and (ii) it is the actor and primary recipients whom an adaptation foremost affects. The categories of social action are thus instrumental to any account of evolved function.

The importance of being explicit

Van Lange et al. propose that climate affects violence via its effects on life history. That much is reasonable (and not novel), but their theory lacks causal specificity. Their foundational claim of an association between heat and violence is not well documented, and several findings that the authors themselves cite seem inconsistent with their model, rather than supportive.