The directional tuning of the barber-pole illusion.

In order to study the integration of local motion signals in the human visual system, we measured directional tuning curves for the barber-pole illusion by varying two crucial aspects of the stimulus layout independently across a wide a range in the same experiment. These were the orientation of the grating presented behind the rectangular aperture and the aspect ratio of the aperture, which in combination determine the relative contributions of local motion signals perpendicular to the gratings and parallel to the aperture borders, respectively. The strength of the illusion, ie the tendency to perceive motion along the major axis of the aperture, obviously depends on the spatial layout of the aperture, but also on grating orientation. Subjects were asked which direction they perceived and how compelling their motion percept was, revealing different strategies of the visual system to deal with the barber-pole stimulus. Some individuals respond strongly to the unambiguous motion information at the boundaries, leading to multistable percepts and multimodal distributions of responses. Others tend to report intermediate directions, apparently being less influenced by the actual boundaries. The general pattern of deviations from the motion direction perpendicular to grating orientation--a decrease with aspect ratio approaching unity (ie square-shaped apertures) and with gratings approaching parallel orientation to the shorter aperture boundary--is discussed in the context of simple phenomenological models of motion integration. The best fit between model predictions and experimental data is found for an interaction between two stimulus parameters: (i) cycle ratio, which is the sine-wave gratings equivalent of the terminator ratio for line gratings, describing the effects from the aperture boundaries, and (ii) the grating orientation, responsible for perpendicular motion components, which describes the influence of motion signals from inside the aperture. This suggests that the most simple cycle (terminator) ratio explanation cannot fully account for the quantitative properties of the barber-pole illusion.     

Sexual Orientation in Adolescents Who Commit Suicide

It has been suggested that there is a strong relationship between suicidal behavior and homosexuality in adolescence. It has been further suggested that it is due to the stigmatization and feelings of isolation that are experienced by many gay adolescents. Much of the literature that has given support to these hypotheses has been conducted on uncontrolled nonrepresentative samples and its generalizability is open to question. An opportunity to examine the relationship in an unselected sample arose in a case control, psychological autopsy study of 120 of 170 consecutive suicides under age 20 and 147 community age, sex, and ethnic matched controls living in the Greater New York City area. Homosexuality was defined as having had homosexual experiences or having declared a homosexual orientation. Three teenagers and no controls met these criteria. The difference was not significant. The circumstances of death were examined and are described. In no instance did suicide directly follow an episode of stigmatization. All three suicides had evidence of significant psychiatric disorder before death. In spite of opportunities for biased reporting, it is concluded that this study finds no evidence that suicide is a common characteristic of gay youth, or that when suicide does occur among gay teenagers, that it is a direct consequence of stigmatization or lack of support.     

Student Learning Communities as Builders of Collective Efficacy

Abstract

Using the evidence from teacher professional learning communities, we explore the ways in which students can collaborate and build their collective efficacy.     

Prereading Deficits in Children in Foster Care

Reading skills are core competencies in children's readiness to learn and may be particularly important for children in foster care, who are at risk for academic difficulties and higher rates of special education placement. In this study, prereading skills (phonological awareness, alphabetic knowledge, and oral language ability) and kindergarten performance of 63 children in foster care were examined just prior to and during the fall of kindergarten. The children exhibited prereading deficits with average prereading scores that fell at the 30(th) to 40(th) percentile. Variations in prereading skills (particularly phonological awareness) predicted kindergarten teacher ratings of early literacy skills in a multivariate path analysis. These findings highlight the need for interventions focused on prereading skills for children in foster care.