Psychology

Co-evolution can give rise to the “Red Queen effect”, where interacting populations alter each other's fitness landscapes. The Red Queen effect significantly complicates any measurement of co-evolutionary progress, introducing fitness ambiguities where improvements in performance of co-evolved individuals can appear as a decline or stasis in the usual measures of evolutionary progress. Unfortunately, no appropriate measures of fitness given the Red Queen effect have been developed in artificial life, theoretical biology, population dynamics, or evolutionary genetics. We propose a set of appropriate performance measures based on both genetic and behavioral data, and illustrate their use in a simulation of co-evolution between genetically specified continuous-time noisy recurrent neural networks which generate pursuit and evasion behaviors in autonomous agents.

Genetic influences on personality differences are ubiquitous, but their nature is not well understood. A theoretical framework might help, and can be provided by evolutionary genetics. We assess three evolutionary genetic mechanisms that could explain genetic variance in personality differences: selective neutrality, mutation-selection balance, and balancing selection. Based on evolutionary genetic theory and empirical results from
behaviour genetics and personality psychology, we conclude that selective neutrality is largely irrelevant, that mutation-selection balance seems best at explaining genetic
variance in intelligence, and that balancing selection by environmental heterogeneity seems best at explaining genetic variance in personality traits.We propose a general model of heritable personality differences that conceptualises intelligence as fitness components
and personality traits as individual reaction norms of genotypes across environments, with different fitness consequences in different environmental niches. We also discuss the place of mental health in the model. This evolutionary genetic framework highlights the role of
gene-environment interactions in the study of personality, yields new insight into the person-situation-debate and the structure of personality, and has practical implications for
both quantitative and molecular genetic studies of personality.

Evolutionary psychology has revolutionized research on human mate choice and sexual attraction in recent years, combining a rigorous Darwinian framework based on sexual
selection theory with a loosely cognitivist orientation to task analysis and mechanism modelling. This hard Darwinian, soft computational approach has been most successful
at revealing the adaptive logic behind physical beauty, demonstrating that many sexual cues computed from face and body shape are not arbitrary, but function as reliable
indicators of phenotypic and genetic quality. The same approach could be extended from physical to psychological cues if evolutionary psychology built stronger ties with
personality psychology, psychometrics and behavioral genetics. A major challenge for mate choice research is to develop more explicit computational models at three levels,
specifying: (1) the perceptual adaptations that register sexual cues given sensory input, (2) the judgment adaptations that integrate multiple cues into assessments of overall attractiveness, and (3) the search strategies that people follow in trying to form mutually attracted pairs. We describe both recent efforts and possible extensions in
these directions. The resulting confluence between evolutionary principles, cognitive models and game-theoretic insights can put mate choice research at the vanguard of an emerging ‘evolutionary cognitive science’ more concerned with domain-specific mental
adaptations than with domain-general intelligence.

Friedrich Nietzsche, male, aged 27, published his first book The birth of tragedy in January 1872, barely a year after Charles Darwin published The descent of man, and Selection in relation to sex.  Both books viewed human culture as a natural outcome of human sexuality and animal instinct.  Although both were widely read and discussed, their views on the origins of human culture were widely forgotten.  The assumption they were attacking, that culture is an autonomous sphere of human activity and belief above the biology of behaviour and instinct, persists as the dominant framework for thinking about the evolution of culture.  That framework has provoked much writing about cultural transmission, memes, and gene-culture co-evolution.  However, it has signally failed to deliver a good theory about what evolutionary selection pressures actually shaped the human capacity for producing and understanding concrete instances of ‘culture’.  This chapter suggests that, a century and a quarter after Nietzsche and Darwin, cultural theory and sexual selection theory have advanced enough that we should once more consider their subversive idea: cultural behaviour is very much more instinctive in nature and sexual in function than most cultured people would care to admit.

Conspicuous displays of consumption and benevolence might serve as “costly signals” of desirable mate
qualities. If so, they should vary strategically with manipulations of mating-related motives. The authors
examined this possibility in 4 experiments. Inducing mating goals in men increased their willingness to spend on conspicuous luxuries but not on basic necessities. In women, mating goals boosted public—but not private— helping. Although mating motivation did not generally inspire helping in men, it did induce more helpfulness in contexts in which they could display heroism or dominance. Conversely, although mating motivation did not lead women to conspicuously consume, it did lead women to spend more publicly on helpful causes. Overall, romantic motives seem to produce highly strategic and sex-specific
self-presentations best understood within a costly signaling framework.

Schizophrenia remains an evolutionary paradox. Its delusions, hallucinations and other symptoms begin in adolescence or early adulthood and so devastate sexual relationships and reproductive success that selection should have eliminated the disorder long ago. Yet it persists as a moderately heritable disorder at a global 1% prevalence—too high for new mutations at a few genetic loci. We suggest that schizophrenia persists and involves many loci because it is the unattractive, low-fitness extreme of a highly variable mental trait that evolved as a fitness (‘‘good genes’’) indicator through mutual mate choice. Here we show that this hypothesis explains many key features of schizophrenia and predicts that some families carry modifier alleles
that increase the indicator’s neurodevelopmental sensitivity to heritable fitness and condition. Such alleles increase the extent to which high-fitness family members develop impressive courtship abilities and achieve high reproductive success, but also increase the extent to which low-fitness family members develop schizophrenia. Here we introduce this fitness indicator model of schizophrenia, discuss its explanatory power, explain how it resolves the evolutionary paradox, discuss its implications for gene hunting, and identify some empirically testable predictions as directions for further research.

Just as body symmetry reveals developmental stability at the morphological level, general intelligence may reveal developmental stability at the level of brain development and cognitive functioning. These two forms of developmental stability may overlap by tapping into a “general fitness factor.” If so, then intellectual tests with higher g-loadings should show higher correlations with a composite measure of body symmetry. We tested this prediction in 78 young males by measuring their left–right symmetry at 10 body points, and by administering five cognitive tests with diverse g-loadings. As predicted, we found a significant (z=3.64, p<0.003) relationship between each test's rank order g-loading and its body symmetry association. We also found a substantial correlation (r=0.39, p<0.01) between body symmetry and our most highly g-loaded test (Ravens Advanced Progressive Matrices). General intelligence is apparently a valid indicator of general developmental stability and heritable fitness, which may partly explain its social and sexual attractiveness.