The size-constancy of underwater swimmers

The size-constancy of divers was measured by requiring them to adjust the distance between two disks of unequal size so that they appeared phenomenally equal. In clear water divers showed greater constancy-ratios than on land. In murky water, where visibility was reduced by suspended particles, constancy-ratios were the same as, or less than, on land. It is suggested that these effects may be due to changes in apparent distance: in clear water objects appear nearer through refraction, but in murky water they appear further away because of the distance cues provided by the visibility gradient.

The orientation of the display, or of the diver's body, did not affect constancy under water, though it does on land. It is argued that the effect on land is due to visual and proprioceptive cues which are absent in the water.     

Some Effects of Reduction of Extra-Classroom Crowding in a School Environment

The effects of reduced enrollment were studied by examining two architecturally identical schools. One school experienced a 43% reduction in enrollment while the other's enrollment remained constant. Reduction in enrollment had a number of positive benefits, including improved attitudes about the school environment and reduced faculty absenteeism. Findings regarding academic performance were less clear.     

Dynamic changes in work/rest duty cycles in a study of sleep deprivation

The effects of moderate workload and 72 h of sleep deprivation were studied using a modified continuous-performance paradigm. Ten subjects were tested hourly on a number of perceptual and cognitive tasks designed to require approximately 30 min to complete, with the remainder of each hour free. As sleep deprivation continued, the average time on task increased at an accelerating rate. The rate of increase differed among tasks, with longer tasks showing greater absolute and relative increases than shorter ones. Such increases confound sleep deprivation and workload effects. In this paper, we compare the advantages and disadvantages of several experimental paradigms; describe details of the present design; and discuss methodological problems associated with separating the interactions of sleep deprivation, workload, and circadian variation with performance.     

Bayesian inference for psychology. Part II: Example applications with JASP

Bayesian hypothesis testing presents an attractive alternative to p value hypothesis testing. Part I of this series outlined several advantages of Bayesian hypothesis testing, including the ability to quantify evidence and the ability to monitor and update this evidence as data come in, without the need to know the intention with which the data were collected. Despite these and other practical advantages, Bayesian hypothesis tests are still reported relatively rarely. An important impediment to the widespread adoption of Bayesian tests is arguably the lack of user-friendly software for the run-of-the-mill statistical problems that confront psychologists for the analysis of almost every experiment: the t-test, ANOVA, correlation, regression, and contingency tables. In Part II of this series we introduce JASP (http://www.jasp-stats.org), an open-source, cross-platform, user-friendly graphical software package that allows users to carry out Bayesian hypothesis tests for standard statistical problems. JASP is based in part on the Bayesian analyses implemented in Morey and Rouder’s BayesFactor package for R. Armed with JASP, the practical advantages of Bayesian hypothesis testing are only a mouse click away.     

Altered stress responses in children exposed to early adversity: a systematic review of salivary cortisol studies

Pathological stress responses are implicated in numerous disorders. Hypothalamic-pituitary-adrenal axis function is influenced by gene-environment interaction, with early-life environmental adversity having long-lasting effects. We examine the evidence that, in humans, these effects are apparent from infancy. We systematically reviewed published findings on cortisol response to a stressor, in 0-5-year-olds already exposed to adversity. Adversity was defined as a negative environmental influence present post-conception. We searched Ovid MEDLINE (1950-May 2010), EMBASE (1980-May 2010) and PsychINFO (1806-May 2010). We included peer-reviewed, English language studies that analysed salivary cortisol before and after a standardised stressor. We identified 30 studies, of which 27 reported a significant effect of adversity on the cortisol response to stress. Six of these demonstrated an effect of prenatal substance exposure. Thirteen studies found that psychosocial adversity increased cortisol reactivity. Three studies reported that cortisol reactivity could be normalised by intervention programmes. The studies were heterogeneous, both in nature of adversity studied and in stressor used, precluding meta-analysis and assessment of publication bias. Our review presents evidence that adversity disrupts the stress response from an early age. Longitudinal studies are required to determine whether effects persist, alter with time, or are reversible with intervention.     

Accounting for fluctuations in body dissatisfaction

The present study evaluated whether the strength of relationship between contextual cues (presence of company and mood) and state body dissatisfaction varied as a function of individual differences in key trait measures (body shame, body surveillance tendencies, internalization of appearance standards, and trait affect) which have been linked to trait body dissatisfaction. Fifty-five undergraduate women completed a questionnaire containing the trait-based measures and then carried a Personal Digital Assistant (PDA) for a 7-day period. The PDA prompted participants six times daily to self-report their current mood and state body dissatisfaction. Multi-level modeling revealed that individual differences in body shame predicted inter-individual variability in the strength of the relationships between presence of company and state body dissatisfaction, and positive mood and state body dissatisfaction. Trait positive affect also explained variance in the positive mood state-body dissatisfaction relationship. The implications of the findings for prevention of body image disturbances are discussed.