Rebecca L. Burch

Reactions to children's faces: Resemblance affects males more than females

Abstract Since cuckoldry risk is asymmetrical, we hypothesized that parental investment would be more affected by paternal than maternal resemblance. To test this hypothesis, we asked subjects hypothetical questions about investing in children under conditions in which their faces or those of other people had been morphed with photographs of children. Males were more likely to choose a face they had been morphed with as the most attractive, the child they were most likely to adopt, the child they would like to spend the most time with, the child they would spend US

Perceptions of paternal resemblance predict family violence.

50 on, and the child they would least resent having to pay child support for. Reactions to childrens faces by females were much less affected by resemblance.

The human penis as a semen displacement device

Fifty-five men participating in a domestic violence treatment program agreed to complete a questionnaire and rate the degree to which their children looked like them. Ratings of paternal resemblance were positively correlated with the self-reported quality of the mens relationships with their children and inversely proportional to the severity of injuries suffered by their spouses. Analogous results were also found for the mens experience with their parents. We suggest that these results reflect mens use of paternal resemblance to assess paternity.

How much paternal resemblance is enough? Sex differences in hypothetical investment decisions but not in the detection of resemblance

Inanimate models were used to assess the possibility that certain features of the human penis evolved to displace semen left by other males in the female reproductive tract. Displacement of artificial semen in simulated vaginas varied as a function of glans/coronal ridge morphology, semen viscosity, and depth of thrusting. Results obtained by modifying an artificial penis suggest that the coronal ridge is an important morphological feature mediating semen displacement. Consistent with the view of the human penis as a semen displacement device, two surveys of college students showed that sexual intercourse often involved deeper and more vigorous penile thrusting following periods of separation or in response to allegations of female infidelity.

Pregnancy as a stimulus for domestic violence

Abstract Subjects presented with an array of childrens faces, which had been morphed to resemble the subject to varying degrees, were asked to make hypothetical investment decisions. Although females were relatively indifferent to resemblance, males reacted favorably towards childrens faces that contained 25% or more of their characteristics. This difference was not a byproduct of differences in the detection of resemblance since males were no better than females at matching child faces with adult faces.

Semen Displacement as a Sperm Competition Strategy in Humans

Data collected from a domestic violence prevention and treatment program were analyzed to determine the relationship between female reproductive status and violent incidents. Both the frequency and severity of male initiated violence against women were twice as high when they were pregnant. These results are discussed in the context of an evolutionary perspective on domestic violence.

Does Semen Have Antidepressant Properties

We examine some of the implications of the possibility that the human penis may have evolved to compete with sperm from other males by displacing rival semen from the cervical end of the vagina prior to ejaculation. The semen displacement hypothesis integrates considerable information about genital morphology and human reproductive behavior, and can be used to generate a number of interesting predictions.

Sex differences in olfactory self-recognition.

In a sample of sexually active college females, condom use, as an indirect measure of the presence of semen in the reproductive tract, was related to scores on the Beck Depression Inventory. Not only were females who were having sex without condoms less depressed, but depressive symptoms and suicide attempts among females who used condoms were proportional to the consistency of condom use. For females who did not use condoms, depression scores went up as the amount of time since their last sexual encounter increased. These data are consistent with the possibility that semen may antagonize depressive symptoms and evidence which shows that the vagina absorbs a number of components of semen that can be detected in the bloodstream within a few hours of administration.

Semen displacement as a sperm competition strategy

This study investigated sex differences in the ability to recognize ones own body odor accompanied by an attempt to account for variance in this ability by comparing ratings of self-body odor and other odors on a visual analog scale (VAS). Whereas over half (59.4%) of the females were able to identify their own odor, only one out of 18 (5.6%) males were able to recognize their own odor. Females rated their own secretions as significantly lower on a pleasant-positive factor than males rated their own odors (axillary secretions), but there was no difference in ratings between those who could and those who could not identify their own odor. The dimensions tapped by the VAS used in this study do not seem to account for the ability to identify ones own body odors.

Female Infidelity and Paternal Uncertainty: The psychobiology of human semen

Using a sample of 652 college students, we examined several implications of the hypothesis that the shape of the human penis evolved to enable males to substitute their semen for those of their rivals. The incidence of double mating by females appears sufficient to make semen displacement adaptive (e.g., one in four females acknowledge infidelity, one in eight admit having sex with two or more males in a 24-hour period, and one in 12 report involvement in one or more sexual threesomes with two males). We also document several changes in post-ejaculatory behavior (e.g., reduced thrusting, penis withdrawal, loss of an erection) which may have evolved to minimize displacement of the male’s own semen. Consistent with predictions derived from a theoretical model (Gallup and Burch 2006), we discovered that most females report waiting at least 48 hours following an instance of infidelity before resuming sex with their in-pair partners.