Pigeons' preference for variable-interval water reinforcement under widely varied water budgets.

Water budget of pigeons was varied to assess the dependence of risk-sensitive preferences upon economic context such as has been reported for energy-budget manipulations with small animals in behavioral ecology research. Fixed- and variable-interval terminal-link water schedules reinforced choice between equal variable-interval initial-link schedules arranged on two pecking keys. While keeping a severely restrictive budget the same across three phases of the experiment, a contrasting distinct ample budget was arranged in each. To mimic typical methods in behavioral ecology studies, in each ample budget a more than three-fold increase in amount of water per reinforcer presentation was instituted simultaneously with significantly increased overall access to water. Total choice response rates plummeted in the ample budgets, and body weights either increased significantly or remained unchanged in different phases as expected by the nature of the different manipulations. Clear preferences for the variable-interval schedule were found throughout the experiment, except for rare instances of key bias. The results agree with similar operant food-reinforcement studies and extend conditions under which risk preference apparently does not depend upon economic context.     

“上善若水”之我见

“上善若水”是道祖老子指导人们修身养性、为人处世、治国平天下的至理名言。何谓“上善”?“上善”是老子理想中最具备完美品德的圣人。道教圣典《道德经》八章中,老子形象地用自然界最不可少的,而最柔弱不争的水之品性来喻圣人之德行,正是因为“水善利万物而不争”,“处众人     

Peripheral stimuli and stereoacuity under water

A variety of attempts were made to improve stereoacuity under water by providing limited additional peripheral stimulation. It was concluded that acuity is most improved when the peripheral stimuli are at the same distance from the o as the target. As the peripheral stimuli are moved closer to the 0 than the target, their beneficial effects are decreased, and beyond a certain point, their presence degrades acuity. This effect seems to be enhanced by increasing turbidity of the water, which decreases the contrast of the distant target relative to that of the nearby peripheral stimuli. These and previous findinp implicate several distinct processes in the degradation of stereoacuity in the water.     

Learning about water by hungry rats

In Experiments 1 and 2 hungry rats were trained in a straight alley with consistent food reward (FF), food and nonreward trials intermixed (FN), or food and water trials intermixed (FW). In Experiment 1 rats were tested with nonrewarded trials (extinction) and Groups FN and FW did not differ, both running faster then Group FF. In Experiment 2 rats were tested with consistent water reward, and Group FW ran faster then Group FN, which was superior to Group FF. In Experiment 3, one group of hungry rats was trained on a single alternating schedule of food and water in Phase 1 and was shifted to a single alternating schedule of food and nonreward in Phase 2 (Group FW); the second group (Group FN) received a single alternating schedule of food and nonreward in both phases. When Group FW was shifted to nonreward from water, performance to nonreward was temporarily disrupted. These results indicate that, contrary to previous conclusions, hungry rats can learn about water when drive is strong and food is received in the situation.     

A process model for water jug problems

We develop and evaluate a model for the water jug task in which a subject is required to find a sequence of moves (pouring operations) which produce a specified amount of water in each jug. Experiment 1 was designed to evaluate the meansends, move selection heuristics that are assumed by the model. Experiment 2 tested the model's predictions concerning those aspects of the water jug task that determine problem difficulty.A three stage process model incorporating GPS-like, means-ends heuristics and assumptions concerning the utilization of short- and long-term memory was able to account for differences across problems as well as details of the performance of subjects solving a given problem. We conclude that a GPS-like model that only selects one move at a time (no forward planning of move sequences or setting up of subgoals) can provide a good account of solution behavior in the water jug task.