Default Probability

A probability may be called “default” if it is neither derived from preestablished probabilities nor based on considerations of frequency or symmetry. Default probabilities presumably arise through reasoning based on causality and similarity. This article advances a model of default probability based on a featural approach to similarity. The accuracy of the model is assessed by comparing its predictions to the probabilities provided by undergraduates asked to reason about mammals.     

Media influence on attitudes toward suicide.

This experiment investigated the effects of viewing films on suicide and violence on attitudes toward suicide. Non-suicidal university students were assigned to one of three groups: One group was shown a film about suicide, a second saw a film about violence, and the third saw a neutral film. Perceptions of the appropriateness of suicide and level of emotional arousal were measured by a questionnaire administered before and after the films were shown. Both the suicide and violent film groups showed increases in arousal scores after viewing the films. The results suggest that arousal became linked to cognitions specific to film content as a result of viewing the films dealing with suicide and violence. Other findings suggest that, for the suicide and violent film groups, perceived relations with parents were important predictors of film-induced changes in attitudes toward suicide.     

Motion over the retina and the motion aftereffect.

The motion aftereffect (MAE) was measured with retinally moving vertical gratings positioned above and below (flanking) a retinally stationary central grating (experiments 1 and 2). Motion over the retina was produced by leftward motion of the flanking gratings relative to the stationary eyes, and by rightward eye or head movements tracking the moving (but retinally stationary) central grating relative to the stationary (but retinally moving) surround gratings. In experiment 1 the motion occurred within a fixed boundary on the screen, and oppositely directed MAEs were produced in the central and flanking gratings with static fixation; but with eye or head tracking MAEs were reported only in the central grating. In experiment 2 motion over the retina was equated for the static and tracking conditions by moving blocks of grating without any dynamic occlusion and disclosure at the boundaries. Both conditions yielded equivalent leftward MAEs of the central grating in the same direction as the prior flanking motion, ie an MAE was consistently produced in the region that had remained retinally stationary. No MAE was recorded in the flanking gratings, even though they moved over the retina during adaptation. When just two gratings were presented, MAEs were produced in both, but in opposite directions (experiments 3 and 4). It is concluded that the MAE is a consequence of adapting signals for the relative motion between elements of a display.     

Gaze control in putting.

The gaze of low and higher handicap golfers was assessed while they performed consecutive putts from 3 m, wearing an eye-movement helmet that permitted normal mobility. MANOVA (count and duration), with univariate follow-up, revealed significant differences in gaze between five low (LH, 0-8) and seven higher handicap golfers (HH, 10-16). The LH (ie more highly skilled) golfers were found to use a variable form of gaze control in which longer fixation durations on the ball and target were observed, and there were fewer fixations on the club and surface, with more express saccades and quicker saccades between gaze locations. The HH golfers, in contrast, allocated the same mean durations to each gaze (about 1 s), independent of type of control (fixation, saccade, or tracking) or location (ball, club, target, or surface). In comparing hits to misses, there was an increased probability of hits if the golfers used express saccades to the club during preparation, and a steady fixation on the ball during the backswing/foreswing of the club, as well as a steady fixation on the surface during contact. These results suggest that with the acquisition of the putting skill, there are changes in gaze control, characterized by economy in the number of gaze shifts, the development of priority to specific gaze locations, and economy in the allocation of time between preferred gaze locations. In the discussion two reasons are proposed that may partially explain the results found here, as well as help further our understanding of the role of gaze in targetting skills.     

The role of social supports in the bereavement process of surviving spouses of suicide and natural deaths.

This report examines the changing role of social supports in the bereavement of spouses of elderly suicide and natural deaths, focusing on differences and similarities in relation to gender, time, and mode of death. Measurements were obtained 4 times after death (within 2 months, at 6 months, at 12 months, and at 2 to 2 1/2 years) on 79% of the 108 survivors of elderly suicide, 89% of the 199 natural death survivors, and 79% of the nonbereaved controls. The results indicated that the suicide survivors received significantly less emotional support for their feelings of depression and grief than the natural death survivors, and that they did not confide in the persons in their network any more than the nonbereaved controls did. Women report receiving more support overall than men. A low spot in social supports occurred at the 6-month point after loss for both bereaved groups, but primarily in practical help received by natural death survivors. By the end of the second year, both practical and emotional supports had increased to at least the same level as immediately after death.