The functions of postpartum depression

Evolutionary approaches to parental care suggest that parents will not automatically invest in all offspring, and should reduce or eliminate investment in their children if the costs outweigh the benefits. Lack of paternal or social support will increase the costs born by mothers, whereas infant health problems will reduce the evolutionary benefits to be gained. Numerous studies support the correlation between postpartum depression (PPD) and lack of social support or indicators of possible infant health and development problems. PPD may be an adaptation that informs mothers that they are suffering or have suffered a fitness cost, that motivates them to reduce or eliminate investment in offspring under certain circumstances, and that may help them negotiate greater levels of investment from others. PPD also appears to be a good model for depression in general

Depression as bargaining: The case postpartum

It was recently hypothesized that depression might function, in part, as a bargaining strategy when cooperation imposes a net cost but there are social constraints on defection (Hagen 1999). If so, such social constraints should be associated with depression, and depression in one partner should be associated with increased investment by other partners. Several predictions of this hypothesis were tested using postpartum depression (PPD) as a model for depression in general. The depression levels, abortion attitudes, additional mating opportunities, and investment in childrearing of 240 mothers and fathers with a new child were measured using self report instruments. Mothers were also asked whether the new child was planned and whether it was wanted. Perceived constraints on abortion correlated significantly with PPD levels, but, as predicted, only for mothers with an unplanned or unwanted child. Contrary to predictions, perceived constraints imposed by family and friends did not correlate with PPD levels. Social constraints on the pursuit of extra-pair copulations also correlated significantly with PPD levels, but, as predicted, only for men. As predicted, PPD levels in one spouse correlated significantly with increased investment in childrearing as reported by the other spouse. PPD levels correlated positively with parity for older women with few future reproductive opportunities, as predicted

The bargaining model of depression

Minor depression—low mood often accompanied by a loss of motivation—is almost certainly an adaptation to circumstances that, in ancestral environments, imposed a fitness cost. It is, in other words, the psychic equivalent of physical pain. Major depression is characterized by additional symptoms—such as loss of interest in virtually all activities and suicidality—that have no obvious utility. The frequent association of these severe and disabling symptoms with apparently functional symptoms like sadness and low mood challenges a functional account of depression as a whole. Given that the principle cause of major unipolar depression is a significant negative life event, and that its characteristic symptom is a loss of interest in virtually all activities, it is possible that this syndrome functions somewhat like a labor strike. When powerful others are benefiting from an individual’s efforts, but the individual herself is not benefiting, she can, by reducing her productivity, put her value to them at risk in order to compel their consent and assistance in renegotiating the social contract so that it will yield net fitness benefits for her. In partial support of this hypothesis, depression is associated with the receipt of considerable social benefits despite the negative reaction it causes in others

Music and dance as a coalition signaling system

Evidence suggests that humans have neurological specializations for music processing, but a compelling adaptationist account of music and dance is lacking. The sexual selection hypothesis cannot easily account for the widespread performance of music and dance in groups (especially synchronized performances), and the social bonding hypothesis has severe theoretical difficulties. Humans are unique among the primates in their ability to form cooperative alliances between groups in the absence of consanguineal ties. We propose that this unique form of social organization is predicated on music and dance. Music and dance may have evolved as a coalition signaling system that could, among other things, credibly communicate coalition quality, thus permitting meaningful cooperative relationships between groups. This capability may have evolved from coordinated territorial defense signals that are common in many social species, including chimpanzees. We present a study in which manipulation of music synchrony significantly altered subjects’ perceptions of music quality, and in which subjects’ perceptions of music quality were correlated with their perceptions of coalition quality, supporting our hypothesis. Our hypothesis also has implications for the evolution of psychological mechanisms underlying cultural production in other domains such as food preparation, clothing and body decoration, storytelling and ritual, and tools and other artifacts

Informational Warfare

Recent empirical and theoretical work suggests that reputation was an important mediator of access to resources in ancestral human environments. Reputations were built and maintained by the collection, analysis, and dissemination of information about the actions and capabilities of group members-that is, by gossiping. Strategic gossiping would have been an excellent strategy for manipulating reputations and thereby competing effectively for resources and for cooperative relationships with group members who could best provide such resources. Coalitions (cliques) may have increased members' abilities to manipulate reputations by gossiping. Because, over evolutionary time, women may have experienced more within-group competition than men, and because female reputations may have been more vulnerable than male reputations to gossip, gossiping may have been a more important strategy for women than men. Consequently, women may have evolved specializations for gossiping alone and in coalitions. We develop and partially test this theory

The quantitative measure and statistical distribution of fame

Fame and celebrity play an ever-increasing role in our culture. However, despite the cultural and economic importance of fame and its gradations, there exists no consensus method for quantifying the fame of an individual, or of comparing that of two individuals. We argue that, even if fame is difficult to measure with precision, one may develop useful metrics for fame that correlate well with intuition and that remain reasonably stable over time. Using datasets of recently deceased individuals who were highly renowned, we have evaluated several internet-based methods for quantifying fame. We find that some widely-used internet-derived metrics, such as search engine results, correlate poorly with human subject judgments of fame. However other metrics exist that agree well with human judgments and appear to offer workable, easily accessible measures of fame. Using such a metric we perform a preliminary investigation of the statistical distribution of fame, which has some of the power law character seen in other natural and social phenomena such as landslides and market crashes. In order to demonstrate how such findings can generate quantitative insight into celebrity culture, we assess some folk ideas regarding the frequency distribution and apparent clustering of celebrity deaths.Comment: 17 pages, 6 figure

Neutron scattering from disordered antiferromagnetic insulators

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Basement structure of the northern Ontong Java Plateau

Site surveys conducted in conjunction with Leg 130 on the Ontong Java Plateau reveal a strong seismic reflector at 0.8 to 1.0 s below the seafloor that drilling at Sites 803 and 807 confirmed is Cretaceous basalt. This reflector is generally smooth, except for the northeastern margin of the plateau, where it forms a series of small, irregularly shaped depressions. Correlatable reflectors present at the bottom of the depressions are also present on the adjacent highs, suggesting that these depressions are original volcanic topography. A strong sub-basalt reflector occurs on many seismic profiles on the northeastern portion of the plateau. This reflection may be caused by a density and velocity contrast between pillow lavas and flood basalt flows or it may result from interbedded sediment and thus may represent significant lulls in volcanic activity. The presence of sub-basalt reflectors near Site 803 may indicate that later volcanic episodes occurred there, in contrast to Site 807, where this reflector was not observed and where older basalt ages were obtained

Strength is negatively associated with depression and accounts for some of the sex difference A replication and extension

Background Depression occurs about twice as often in women as in men, a disparity that remains poorly understood. In a previous publication, Hagen and Rosenstrom predicted and found that grip strength, a highly sexually dimorphic index of physical formidability, mediated much of the effect of sex on depression. Striking results like this are more likely to be published than null results, potentially biasing the scientific record. It is therefore critical to replicate and extend them. Methodology Using new data from the 2013-14 cycle of the National Health and Nutrition Examination Survey, a nationally representative sample of US households (n = 3650), we replicated models of the effect of sex and grip strength on depression reported in Hagen and Rosenstrom, along with additional potential confounds and a new detailed symptom-level exploration. Results Overall, the effects from the original paper were reproduced although with smaller effect sizes. Grip strength mediated 38% of the effect of sex on depression, compared to 63% in Hagen and Rosenstrom. These results were extended with findings that grip strength had a stronger association with some depression symptoms, like suicidality, low interest and low mood than with other symptoms, like appetite changes. Conclusions Grip strength is negatively associated with depression, especially its cognitive-affective symptoms, controlling for numerous possible confounds. Although many factors influence depression, few of these reliably occur cross-culturally in a sex-stratified manner and so are unlikely to explain the well-established, cross-cultural sex difference in depression. The sex difference in upper body strength occurs in all populations and is therefore a candidate evolutionary explanation for some of the sex difference in depression. Lay summary: Why are women at twice the risk of developing depression as men? Depression typically occurs during social conflicts, such as physical or sexual abuse. Physically strong individuals can often single-handedly resolve conflicts in their favor, whereas physically weaker individuals often need help from others. We argue that depression is a credible cry for help. Because men generally have greater strength than women, we argue that men may be more likely to resolve conflicts using physical formidability and women to signal others for help. We find that higher grip strength is associated with lower depression, particularly symptoms like feeling down or thoughts of suicide and that strength accounts for part of the sex difference in rates of depression.Peer reviewe