Behavioral contrast as a function of the temporal location of reinforcement

Pigeons were trained on a multiple variable-interval variable-interval schedule of reinforcement. One component was then changed to a variation of a fixed-interval schedule in which the same rate of reinforcement was obtained as previously but the location of the reinforcer was fixed within the component. The effects of different temporal locations were compared. An increase in response rate for the unchanged variable-interval component (behavioral contrast) occurred when the reinforcer was located in the middle or at the end of the FI component, but response suppression occurred when it was located at the beginning of the component. The pattern of results cannot be explained by any previous theories of contrast. The overall response rates, and the pattern of local rates within the components, were consistent with the hypothesis that the major determinant of the contrast effect was the transition to a lower reinforcement rate following the unchanged component.     

Effects of schedule and magnitude of reinforcement under conditions of thirst motivation

In contrast to a recent finding (Macdonald, G. E., & De Toledo, L. Learning and Motivation, 1974, 5, 288–298.) the results of three experiments investigating various partial reinforcement (PRF) manipulations under conditions of thirst motivation demonstrated strong similarity to analogous manipulations involving food reward. Specifically, for animals receiving water reinforcement, PRF was shown to generate greater resistance to extinction than continuous reinforcement (Expt 1 & 3), the schedule of reinforcement was shown to interact with level of acquisition (Expt 1 and 2), and the magnitude of the partial reinforcement extinction effect was shown to be a function of reward magnitude (Expt 3). These results provide strong evidence that mechanisms which operate in partial reinforcement situations are highly similar, regardless of the type of appetitive reinforcement.     

The KKK won't let me play: ostracism even by a despised outgroup hurts

Previous research has shown that ostracism even by outgroup members is aversive. In this study we examined whether ostracism by a particular type of outgroup, a despised outgroup, was sufficient to inflict emotional distress. We manipulated ostracism using Cyberball, an on-line ball toss game. Ostracized participants reported lower levels of belonging, self-esteem, control, and meaningful existence, and more negative mood, than included participants. Moreover, ostracism by despised outgroup members was no less aversive than ostracism by rival outgroup or ingroup members. Participants differentiated between the groups, however; ostracized individuals reported greater outgroup negativity than included participants only when their co-players were members of the despised outgroup. We interpret these results as evidence for the powerful impact of ostracism and the potential importance of distinguishing between qualitatively different outgroups. Copyright © 2006 John Wiley & Sons, Ltd.     

Disappearance of afterimages at 'impossible' locations in space

An eccentrically positioned afterimage, viewed in the dark, will disappear if the eye is positioned so that the afterimage now projects to a more extreme location relative to straight ahead. It was found that the afterimage disappeared when it projected to a location which corresponded to the edge of the visual field defined by the brow, cheek, and nose. This suggests that visibility of stimuli from those retinal regions shadowed by the head is influenced by eye-position information.