Suicidal Behavior in Relatives or Associates Moderates the Strength of Common Risk Factors for Suicide

The prevalence and odds ratios of different suicide risk factors were compared in three pairs of decedents: 80 suicides and 25 injury decedents with blood relatives with suicidal behavior history (biologically exposed); 259 suicides and 126 injury decedents with unrelated acquaintances with suicidal behavior history (socially exposed); and 471 suicides and 523 injury decedents with neither relatives nor acquaintances with suicidal behavior history (unexposed). Negative life events and high psychological stress were more common in socially exposed suicides than in other suicides. The adjusted odds ratios of most established suicide risk factors were higher in unexposed decedents than in biologically or socially exposed decedents, suggesting that the predictive value of established risk factors wanes in individuals who have been exposed to suicidal behavior in family or friends.     

Information concentration along the boundary contours of naturally shaped solid objects.

In this study of the informativeness of boundary contours for the perception of natural object shape, observers viewed shadows/silhouettes cast by natural solid objects and were required to adjust the positions of a set of 10 points so that the resulting dotted shape resembled the shape of the original silhouette as closely as possible. For each object, the observers were then asked to indicate the corresponding positions of the 10 points on the original boundary contour. The results showed that there was a close correspondence between the chosen positions of the points and the locations along the boundary contour that were local curvature maxima (convexities or concavities). This finding differs from that of Kennedy and Domander (1985 Perception 14 367-370), and shows that, at least for natural objects, the original hypothesis of Attneave (1954 Psychological Review 61 183-193) is valid--local curvature maxima are indeed important for the perception of shape.