Effects of alternative reinforcement on human behavior: the source does matter

Competing theories regarding the effects of delivering periodic response-independent reinforcement (more accurately, response-independent points exchanged for money) on a baseline rate of behavior were evaluated in human subjects. Contiguity theory holds that these events decrease target responding because incompatible behavior is adventitiously strengthened when the point deliveries follow target behavior closely in time. Matching theory holds that response-independent points, like any other alternative reinforcer, should reduce target responding. On this view, temporal contiguity between target responding and response-independent point delivery is unimportant. In our experiment, four different responses (moving a joystick in four different directions) were reinforced with points exchangeable for money according to four independent variable-interval schedules. Different schedules of point delivery were then superimposed on these baselines. When all superimposed point deliveries occurred immediately after one of the four responses (the target response), time allocated to target responding increased. When the superimposed point deliveries could be delivered at any time, time allocated to target responding declined and other behavior increased. When superimposed points could never immediately follow target responses, time allocated to target responding decreased further and other behavior or pausing predominated. The findings underscore the contribution of temporal contiguity in the effects of response-independent deliveries of food, money, points, etc.     

The Mpowerment Project: community-building with young gay and bisexual men to prevent HIV1

The Mpowerment Project is a community-level HIV prevention intervention for young gay and bisexual men ages 18–27. The program seeks to build a strong, supportive young gay and bisexual men's community where young gay and bisexual men nurture and protect each other, particularly with regard to HIV prevention. The program's theoretical framework draws from the areas of diffusion of innovations, community organizing, peer influence, and personal empowerment. The Mpowerment Project promotes a norm for safer sex through a variety of social, outreach and small group activities. The project is run by a Core Group of 12–15 young gay and bisexual men who, with volunteers, design and carry out all project activities. Implemented in 4 communities (Eugene, OR; Santa Barbara, CA; Albuquerque, NM; Austin, TX), the Mpowerment Project has proven to be effective in reducing high risk sex. This paper discusses the development and implementation of the program and various challenges encountered.     

Is temporal spacing of tests helpful even when it inflates error rates?

The occurrence of errors is often thought to impede associative learning. This was tested in 2 studies, each of which involved 2 sessions. In Session 1, subjects learned foreign vocabulary (Experiment 1) or obscure English words (Experiment 2) and received 2 tests (each with corrective feedback) separated by a variable lag. Greater lags drastically reduced performance on the 2nd test. However, they dramatically improved performance in a Session-2 test given 1 day (Experiment 1) or 1 week later (Experiment 2). This pattern held even for items that elicited errors on the 1st test of Day 1. Evidently, the benefit of spacing overwhelms any possible harmful effect of producing errors. The results have clear and nonobvious implications for computer-aided instruction.     

Detecting changes between real-world objects using spatiochromatic filters

A behavioral and computational treatment of change detection is reported. The behavioral task was to judge whether a single object substitution change occurred between two “flickering” 9-object scenes. Detection performance was found to vary with the similarity of the changing objects; object changes violating orientation and category yielded the fastest and most accurate detection responses. To account for these data, theBOLAR model was developed, which uses color, orientation, and scale selective filters to compute the visual dissimilarity between the pre- and postchange objects from the behavioral study. Relating the magnitude of the BOLAR difference signals to change detection performance revealed that object pairs estimated as visually least similar were the same object pairs most easily detected by observers. The BOLAR model advances change detection theory by (1) demonstrating that the visual similarity between the change patterns can account for much of the variability in change detection behavior, and (2) providing a computational technique for quantifying these visual similarity relationships for real-world objects.     

Where Do We Go from Here?

Beginning with the End represents an excellent collection of articles devoted to the thought of Wolfhart Pannenberg. This volume includes many of the most important thinkers in the science-religion dialogue and shows as well the importance and impact of Pannenberg's theology. This response addresses themes that surface in several of the articles: What is religion? What is science? What is theology? What is God? On some of these themes there is agreement, on others sharp disagreement. The conclusion also considers what this volume suggests about the future of Pannenberg's theology.