Animal Learning & Behavior最新文献

Pigeons responded on concurrent-chain schedules with variable-interval initial links and equal delays as terminal links. The terminal-link delays were 1 sec in some conditions and 20 sec in other conditions. The percentages of reinforcers delivered for responses on the left key were 10%, 30%, 70%, or 90%, and this percentage was switched every five to nine sessions. The rate of change in the pigeons' response percentages after a switch was the same whether the terminal-link delays were 1 sec or 20 sec. Analysis of the effects of individual reinforcers showed that after a response on one key had been reinforced, response percentages on that key were higher for at least the next 100 responses. Small effects of individual reinforcers were evident after eight or nine additional reinforcers had been delivered. The effects of individual reinforcers were about equally large during times of transition and during periods in which overall response percentages were relatively stable.

Searches conducted with Medline and PsycInfo showed that the number of publications dealing with learning in animals increased between 1975 and 2000 and that the increase was substantially greater in Medline than in PsycInfo. An examination of major journals dealing with behavioral studies of conditioning and learning for the years 1953, 1963, 1973, 1983, 1993, and 2000 revealed a different pattern of results. The number of papers published in these journals increased from 1953 to 1973 but has been declining steadily since then. However, this decline was partially offset by an increase in the number of experiments published in each paper. Substantially more experiments were published in 2000 than in 1963 or 1953. The number of core authors in the field also peaked in 1973 and has been declining since. However, there were only seven fewer core authors in 2000 than in 1983, and 1983 had as many core authors as 1963. These data suggest that pessimism about the status of behavioral studies of learning is not warranted if research activity is considered over a 40-year period. Furthermore, increased interest in the neural and biological mechanisms of learning should bode well for the status of behavioral research, because one cannot examine the physiological mechanisms of a behavioral process without first clearly understanding the phenomenon at the behavioral level.

In the bidirectional control procedure, observers are exposed to a conspecific demonstrator responding to a manipulandum in one of two directions (e.g., left vs. right). This procedure controls for socially mediated effects (the mere presence of a conspecific) and stimulus enhancement (attention drawn to a manipulandum by its movement), and it has the added advantage of being symmetrical (the two different responses are similar in topography). Imitative learning is demonstrated when the observers make the response in the direction that they observed it being made. Recently, however, it has been suggested that when such evidence is found with a predominantly olfactory animal, such as the rat, it may result artifactually from odor cues left on one side of the manipulandum by the demonstrator. In the present experiment, we found that Japanese quail, for which odor cues are not likely to play a role, also showed significant correspondence between the direction in which the demonstrator and the observer push a screen to gain access to reward. Furthermore, control quail that observed the screen move, when the movement of the screen was not produced by the demonstrator, did not show similar correspondence between the direction of screen movement observed and that performed by the observer. Thus, with the appropriate control, the bidirectional procedure appears to be useful for studying imitation in avian species.