The perception of surface curvature from optical motion

Observers viewed the optical flow field of a rotating quadric surface patch and were required to match its perceived structure by adjusting the shape of a stereoscopically presented surface. In Experiment 1, the flow fields included rigid object rotations and constant flow fields with patterns of image acceleration that had no possible rigid interpretation. In performing their matches, observers had independent control of two parameters that determined the surface shape. One of these, called the shape characteristic, is defined as the ratio of the two principle curvatures and is independent of object size. The other, called curvedness, is defined as the sum of the squared principle curvatures and depends on the size of the object. Adjustments of shape characteristic were almost perfectly accurate for both motion conditions. Adjustments of curvedness, on the other hand, were systematically overestimated and were not highly correlated with the simulated curvedness of the depicted surface patch. In Experiment 2, the same flow fields were masked with a global pattern of curl, divergence, or shear, which disrupted the first-order spatial derivatives of the image velocity field, while leaving the second-order spatial derivatives invariant. The addition of these masks had only negligible effects on observers’ performance. These findings suggest that observers’ judgments of three-dimensional surface shape from motion are primarily determined by the second-order spatial derivatives of the instantaneous field of image displacements.     

TRAINING PREDELINQUENT YOUTHS AND THEIR PARENTS TO NEGOTIATE CONFLICT SITUATIONS1

In response to parental requests for assistance in dealing with adolescent problem children, three parent-child pairs were taught negotiation responses to hypothetical conflict situations using behavior rehearsal and social reinforcement. The negotiation process was separated into component behaviors that were practised during simulations by each youth and his parent under the direction of trainers. Results indicated that (a) the procedures were successful in training youths and their parents in negotiation behaviors that produced agreements to conflict situations, and (b) these behaviors generalized to actual conflict situations in subjects' homes.     

Achievement Place: modification of the behaviors of pre-delinquent boys within a token economy

The "pre-delinquent" behaviors of six boys at Achievement Place, a community based family style behavior modification center for delinquents, were modified using token (points) reinforcement procedures. In Exp. I, point losses contingent on each minute late were effective in producing promptness at the evening meal. During the reversal phase, threats (which were not backed up with point losses) to reinstate the point consequences initially improved promptness but the last two of five threats were ineffective. In Exp. II, point consequences effectively maintained the boys' room-cleaning behavior and, during a fading condition where the percentage of days when the contingency occurred was decreased, the point consequences remained effective for over six months, even when they were delivered on only 8% of the days. Experiment III showed that the boys saved considerable amounts of money when point consequences were available for deposits but saved little money when no points were available. Also, when points were given only for deposits that occurred on specific days the boys deposited their money almost exclusively on those days. In Exp. IV, point consequences contingent on the number of correct answers on a news quiz produced the greatest increase in the percentage of boys who watched the news and, to a lesser extent, increased the percentage of correct answers for the boys who watched the news. The results indicate that "pre-delinquent" behaviors are amenable to modification procedures and that a token reinforcement system provides a practical means of modifying these behaviors.