An Empirical Note on Attaining a Spatial Target after Distorting the Initial Conditions of Movement via Muscle Vibration

Can one’s limb be accurately positioned to a spatial location without a veridical estimate of the initial conditions of movement? The experiment reported here examined this question by distorting perception of a limb’s starting position via muscle vibration. Subjects executed rapid flexion movements under no-vibration, contralateral arm vibration, and ipsilateral arm vibration conditions. Vibration was applied to the biceps for 10 sec prior to the start of a reproduction movement. The results showed that vibration on the ipsilateral arm caused a significant increase in reproduction error, relative to the no-vibration and contralateral-vibration conditions. This finding provides additional evidence that accurate knowledge about the initial conditions of movement is a necessary component in positioning a limb.     

An Analysis of Air-Stepping in Normal Infant Vervet Monkeys

Limb movements during air-stepping were analyzed in three neonatal vervet monkeys over a three-week period. The movements had similar temporal organization both across animals and across time. For example, the duration of both the hind and the forelimb cycle equaled about 500 ms, with the hind limb return strokes lasting much longer than the hind limb power strokes. Furthermore, there were clear indications of both intra- and interlimb coordination. Specifically, all the joints of a limb tended to flex and extend simultaneously, and contralateral and ipsilateral limb pairs had an average phase relationship of approximately 50% of cycle duration. Despite a qualitative similarity between limb movements during air-stepping in the neonates and overground locomotion in older animals, there were notable differences both in temporal relationships and joint displacement patterns. Finally, there appeared to be important similarities between air-stepping in these monkeys and stepping in newborn humans. Most notably, both tended to disappear after a limited period. The implications of these similarities, as well as the overall results, are discussed in relation to the understanding of the development of locomotor behavior in human and nonhuman primates, using approaches based both upon the hard-wired and dynamic models.     

Alcohol use and high-risk sexual behavior among men who have sex with men: the effects of consumption level and partner type.

Alcohol use may increase HIV sexual risk behavior, although findings have varied across study populations and methods. Using event-level data from 1,712 seronegative men who have sex with men, the authors tested the hypothesis that social context would moderate the effect of alcohol consumption on unprotected anal sex (UAS). For encounters involving a primary partner, rates of UAS did not vary as a function of alcohol use. However, consumption of 4 or more drinks tripled the likelihood of UAS for episodes involving a nonprimary partner. Thus, the effects of alcohol vary according to the context in which it is used. Interventions to reduce substance-related risk should be tailored to the demands of maintaining sexual safety with nonprimary partners.     

The Relationship Between Effort and Moral Worth: Three Amendments to Sorensen’s Model

Kelly Sorensen defends a model of the relationship between effort and moral worth in which the effort exerted in performing a morally desirable action contributes positively to the action’s moral worth, but the effort required to perform the action detracts from its moral worth. I argue that Sorensen’s model, though on the right track, is mistaken in three ways. First, it fails to capture the relevance of counterfactual effort to moral worth. Second, it wrongly implies that exerting unnecessary effort confers moral worth on an action. Third, it fails to adequately distinguish between cases in which effort is required because of defects of moral character and those in which effort is required because of barriers external to moral character, such as social pressures or non-moral cognitive deficits. I suggest three amendments to Sorensen’s model that correct these three defects.     

Collins’ core fine-tuning argument

Collins (The Blackwell companion to natural theology, 2009) presents an argument he calls the ‘core fine-tuning argument’. In this paper, I show that Collins’ argument is flawed in at least two ways. First, the structure, depending on likelihoods, fails to establish anything about the posterior probability of God’s existence given fine-tuning. As an argument for God’s existence, this is a serious failing. Second, his analysis of what is appropriately restricted background knowledge, combined with the credences of a specially chosen ‘alien’, do not allow him to establish the premise \( \Pr (LPU \mid NSU~ \& ~k') \ll 1\) .     

Peacocks, Picasso, and parental investment: The effects of romantic motives on creativity

Four experiments explored the effects of mating motivation on creativity. Even without other incentives to be creative, romantic motives enhanced creativity on subjective and objective measures. For men, any cue designed to activate a short-term or a long-term mating goal increased creative displays; however, women displayed more creativity only when primed to attract a high-quality long-term mate. These creative boosts were unrelated to increased effort on creative tasks or to changes in mood or arousal. Furthermore, results were unaffected by the application of monetary incentives for creativity. These findings align with the view that creative displays in both sexes may be linked to sexual selection, qualified by unique exigencies of human parental investment.     

Unidimensionality and bandwidth in the Center for Epidemiologic Studies Depression (CES-D) Scale

In this study, we compared classical test theory (CTT) and item response theory (IRT) approaches in analyzing the Center for Epidemiological Studies Depression (CES-D) Scale (Radloff, 1977). Standard item analyses, as well as Rasch (1960) analyses, both revealed item departures from unidimensionality in a sample of 2,455 older persons responding to the CES-D. Positive affect items in the scale performed poorly overall, their removal reducing the scale's bandwidth only slightly. Modeling depression scores derived from Rasch measures and raw totals showed subtle but important differences for statistical inference. The assessment of depressive risk was slightly enhanced by using 16-item scale measures obtained from the results of the Rasch analysis as the dependent variable. Confirmatory factor analysis and parallel analysis verified the advantages of removing positively worded items. IRT and CTT techniques proved to be complementary in this study and can be usefully combined to improve measuring depression.