Binocular cues in the perception of distance of a point source of light

The ability to make egocentric distance estimates of a single point source of light, seen in darkness and without the cues of changing size and luminance, was investigated in sixteen observers. The attenuation required to maintain constant luminance, when the target was viewed from different distances, was shown to follow the inverse square law providing the angle subtended by the light was less than 20 s arc. Distance changes were also simulated by means of a split mirror which produced vergence cues, or by test lenses to provide accommodation cues. Over the range 0.5 to 9.2 m distance estimates were surprisingly accurate, although there was some overestimation of near and underestimation of far distances. Most observers made good judgements when only convergence cues were varied, whereas no observers made consistently good judgements when only accommodation cues were varied. The difficulties are discussed in terms of the accommodation-convergence link. When distance was simulated by changing convergence and accommodation cues, estimates were not as good as when real distance was changed. Since good estimates were made with brief target exposures, these judgements were not based on subsequent convergence or accommodation changes. It is suggested that the metric or reference against which the apparently absolute judgements were made was the efferent demand signal associated with a 'resting' position of convergence in darkness.     

CROWDING,TASK PERFORMANCE,AND COMMUNICATIVE INTERACTION IN YOUTH AND OLD AGE

Following Altman's privacy regulation model, this research was based on the assumption that the relationship between achieved and desired levels of privacy is a major determinant of the experience of crowding in small groups. Further, on the basis of evidence that advancing age is associated with a chronic lack of communicative interaction, it was assumed that the achieved level of privacy among elderly persons generally is greater than that experienced by young adults. Given these assumptions, it was predicted that the crowding threshold of young adults would be significantly lower than that of older persons. To test this hypothesis, the research varied conversation distance (close, far) and density (small room, large room) and assessed the quality of communicative interaction and task performance among small groups of college-age females and retired women over 60 years of age. Results showed that task performance among younger subjects deteriorated in close interaction conditions, whereas the performance of older subjects was improved by spatial intrusion. Further, older subjects exhibited positive communication behaviors in response to close conversation, high-density conditions, while younger subjects responded either with negative communication behaviors or were unaffected by spatial restriction. Finally, the research confirmed previous findings that conversation distance is a more important determinant of the experience of crowding in small groups than physical density. The significance of the results for Altman's privacy regulation model and their implications for the study of human communication behaviors were discussed.     

A longitudinal study of pain sensitivity and blood pressure in adolescent boys: results from a 5-year follow-up.

A growing literature has observed a significant reduction in pain sensitivity among hypertensive animals and humans. It is uncertain whether a reduced sensitivity to pain can be observed in nonnotensive individuals who go on to develop high blood pressure. Blood pressure (BP) was reassessed in one hundred fifteen 19-year-old boys initially tested at age 14, when they were also presented with a pain stimulus (mechanical finger pressure). Hierarchical regression analyses indicated that information regarding pain tolerance improved prediction of changes in systolic and diastolic blood pressure beyond that afforded by differences in BP at age 14, parental history of hypertension, and body mass index. These analyses suggest that pain sensitivity may be associated with physiological processes involved in the development of sustained high blood pressure.