Positive contrast obtained in reacquisition following interpolation of nonreinforced or partially reinforced trials

Two experiments investigated the effects of shifting from either nonreinforcement or partial reinforcement (PRF) to continuous reinforcement conditions (CRF). In the first experiment, three groups of rats were given food reinforcement under CRF conditions in a runway followed by regular extinction trials (RE), extinction trials where Ss were delayed for 30 sec before entering the empty goal box (DE), or CRF trials where Ss were delayed for 30 sec before entering the baited goal box (DF). Then all Ss were run on the delayed reinforcement condition (DF). In the final delayed reinforcement condition, group DE ran significantly faster than group DF, reflecting positive contrast. In the second experiment, four groups of rats were trained in a runway to receive either 4% or 18% sucrose reinforcers under either PRF or CRF conditions. Then all Ss were transferred to a Skinner box and bar presses were continuously reinforced, with each S continuing to receive the same sucrose concentration as before. The former PRF Ss, regardless of the reinforcer, bar pressed at a significantly higher rate in the Skinner box than the former CRF Ss. The evidence seemed to favor the view that the effectiveness of a reinforcer is not an absolute, unchanging quantity but rather depends on the historical context in which the reinforcer occurs.     

Review article

Vie et Mort des Chrétiens d'Orient. Jean‐Pierre Valognes, 1994. Paris, Fayard. 972 pp., FF250, ISBN 2–213–03064–2     

Sailing Through Troubled Waters: Palestinian Christians in the Holy Land

For many people the names "Arab Christians" and "Palestinian Christians" seem to be oxymoronic. Christianity was, however, born in the Middle East, in a little town called Bethlehem. This article explores the ways in which Palestinian Christians, a minority group in both Palestine and Israel, relate to both Jews and Muslims in Palestine and Israel. Though there is no covert persecution of Palestinian Christians, they face the same trials as other Arabs and Muslims in Palestine, due to the current policies and actions of the Israeli government and to the current "war on terrorism." In fact, Christians in Palestine become easy targets for both those enraged by and supportive of the US declaration of war. At the same time, they offer the world an example of healthy Christian–Muslim relations. Perhaps too, Palestinian Christians can be the bridge between the Jewish and Muslim communities in the Holy Land.     

Transfer between downshift in reward magnitude and continuous delay of reward

Two separate experiments were conducted to investigate transfer of persistence between delay and a downshift in reward magnitude. In the first experiment, experimental rats were initially downshifted in reward magnitude and later tested for persistence to continuous delay of large reward. It was found that these rats were more persistent to the effects of delay than control rats which did not receive prior experience with a downshift in reward magnitude. In the second experiment, experimental rats were first trained to receive large reward under delayed conditions and then tested for persistence to a downshift in reward magnitude. Compared to control rats which received no prior experience with delay, the experimental rats showed a significantly smaller negative contrast effect. The results were interpreted as supporting Amsel's theory of persistence as well as Capaldi's recent interpretation of contrast effects.