The pace-of-life syndrome (POLS) hypothesis predicts that behavior and physiology covary with life history. Evidence for such covariation is contradictory, possibly because systematic sources of variation (e.g. sex) have been neglected. Sexes often experience different selection pressures leading to sex-specific allocation between reproduction and self-maintenance, facilitating divergence in life-history. Sex-specific differences in means and possibly variances may therefore play a key role in the POLS framework. We investigate whether sexes differ in means and variances along the fast-slow pace-of-life continuum for life history and physiological and behavioral traits. In addition, we test whether social and environmental characteristics such as breeding strategy, mating system, and study environment explain heterogeneity between the sexes. Using meta-analytic methods, we found that populations with a polygynous mating system or for studies conducted on wild populations, males had a faster pace-of-life for developmental life-history traits (e.g., growth rate), behavior, and physiology. In contrast, adult life-history traits (e.g., lifespan) were shifted towards faster pace-of-life in females, deviating from the other trait categories. Phenotypic variances were similar between the sexes across trait categories and were not affected by mating system or study environment. Breeding strategy did not influence sex differences in variances or means. We discuss our results in the light of sex-specific selection that might drive sex-specific differences in pace-of-life and ultimately POLS.Electronic supplementary materialThe online version of this article (10.1007/s00265-018-2534-2) contains supplementary material, which is available to authorized users.

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The evolution and maintenance of consistent individual differences, so called animal personalities, have attracted much research interest over the past decades. Variation along common personality traits, such as boldness or exploration, is often associated with risk-reward trade-offs. Individuals that are bolder and hence take more risks may be more successful in acquiring resources over the short term. Cautious individuals taking fewer risks may, on the other hand, live longer, but may also gather fewer resources over the short term. According to recent theory, individual differences in personality may be functionally related to individual differences in cognitive performance (i.e., the way in which individuals acquire or use information). Individual differences in the acquisition speed of cognitively challenging tasks are often associated with a speed-accuracy trade-off. Accuracy can be improved by investing more time in the decision-making process or, conversely, decisions can be made more quickly at the cost of making more mistakes. Hence, the speed-accuracy trade-off often involves a risk-reward trade-off. We tested whether 3 personality traits, boldness, activity, and aggressiveness, are correlated with individual learning, associative learning speed, and behavioral flexibility as assessed by reversal learning in wild cavies (Cavia aperea). We found strong positive relationships between all personality traits and learning speed, whereas flexibility was negatively associated with aggressiveness. Our results support the hypothesis that performance reflects individual differences in personality in a predictable way.

Highlights d Quality of human autapses depends on astrocyte type and fetal bovine serum additives d Standardized assays of key morphological, biophysical, and synaptic properties d Standardized assays of short-term plasticity, synaptic depression, and synapse recovery d Some NGN2-induced neurons show multiple/long axons and glutamate-GABA corelease

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