Longitudinal studies of behavior and performance during a winter at the South Pole.

BACKGROUND: Evidence of a specific pattern of performance decrement in isolated and confined (ICE) environments has not been consistently demonstrated in previous research. HYPOTHESIS: Decrements in performance in ICE environments: a) occur in a linear, dose-response manner; b) occur in stages; or c) do not occur at all. METHODS: There were 83 members of the United States Antarctic Program who spent an austral winter at the Amundsen-Scott South Pole Station (90 degrees S) between 1991 and 1994 and completed the Profile of Moods States (POMS) once a month for an 8-mo period from March through October. RESULTS: Over the entire 8-mo period, there was a decline in depression (p = 0.007) and vigor (p < 0.0001), and an increase in fatigue (p = 0.059) and tension-anxiety (p = 0.075). Of these four measures, only vigor exhibits a linear pattern. Mean scores for tension-anxiety and fatigue were lower during the first half of the winter than the second half (p = 0.074 and 0.077, respectively). In comparisons between each quarter and the remaining three quarters, averaged mean tension-anxiety scores and fatigue scores were lower during the second quarter (p = 0.009 and 0.03, respectively), and higher during the fourth quarter (p = 0.025 and 0.035, respectively) than during the previous three quarters combined. CONCLUSIONS: The duration of optimal performance in isolated and extreme environments and the explanation for changes in performance during long duration assignments in such environments both depend on what behavioral measure is used to assess performance.

Human marriage systems and sexual dimorphism in stature.

Contemporary populations of Homo sapiens are sexually dimorphic on a variety of traits. In terms of stature, men are reliably between 4% and 10% taller than women in well-sampled human populations. Are cross-cultural differences in the magnitude of sexual dimorphism consistent with expectations from sexual selection theory? Prior studies have provided conflicting answers to this question in part because they failed to agree on how the force of sexual selection should or could be operationalized. Here we offer a simple and unbiased method for operationalizing sexual selection and retest two separate predictions from earlier work (Alexander et al., 1979) about its expected impact on stature dimorphism in a sample of 155 societies. Neither prediction matches the observed cross-cultural distribution of dimorphism. However, this is not the consequence of a random distribution of dimorphism across societies. Instead, the data exhibit a robust and unexpected pattern.