Are curves detected by 'curvature detectors'?

Five experiments which attempted to evaluate the relationship between orientation and curvature selectivity in human vision are described. In the first two experiments, threshold elevation for curved gratings was measured after exposure to similar gratings, with the use of either an adaptation (experiment 1) or a masking (experiment 2) paradigm. In both experiments threshold elevation occurred which was selective for both the degree and the direction of curvature of the adapting pattern. Experiment 3 compared the effects of adapting to tilted rectilinear or vertical curved gratings upon threshold for a vertical rectilinear grating. Threshold elevation declined systematically as the adapting gratings were either tilted or made more curved. Experiment 4 measured curvature selectivity as a function of the orientation of a curved adapting grating. Threshold elevation declined as the adapting grating was tilted more, but curvature selectivity remained. Experiment 5 measured the orientation tuning for curved gratings directly. Threshold elevation declined to 50% of its maximum value at an adpating orientation of about 28 degrees. This was constant for all values of curvature used. The resulsts are discussed with reference to the question of whether the human visual system contains 'curvature detectors' or linear-contour detectors which respond to the tangents of curves.     

Depression Management Training: A Structured Group Approach

This article describes a structured group program called Depression Management Training (DMT), the focus of which is to increase participants' awareness of the multidimentional sources of depression and to enhance their coping strategies.     

The interference of a baseline with children's orientation judgement need not entirely mask their contextual responsiveness

Children below the age of seven are very influenced by the orientation of the external frame of reference when they attempt to lay down a stimulus to match that of a tilted target. If, however, the target be set upon a baseline the children seem unable to benefit from salient parallel alignment cues. By modifying the usual design it is shown that children can remain able to take their bearings from contextual alignment even when setting a pointer upon a baseline; but the effect is only revealed in a complex three-way interaction. Contextual sensitivity is thus not abolished, but masked; and its re-emergence is in an apparently anomalous form.