Elsevier

Behavioural Processes

Volume 74, Issue 2, 22 February 2007, Pages 286-292
Behavioural Processes

Temporal discrimination learning by pigeons

https://doi.org/10.1016/j.beproc.2006.09.011Get rights and content

Abstract

Memory for time by animals appears to undergo a systematic shortening. This so-called choose-short effect can be seen in a conditional temporal discrimination when a delay is inserted between the sample and comparison stimuli. We have proposed that this temporal shortening may result from a procedural artifact in which the delay appears similar to the intertrial interval and thus, produces an inadvertent ambiguity or ‘instructional failure’. When this ambiguity is avoided by distinguishing the intertrial interval from the delay, as well as the samples from the delay, the temporal shortening effect and other asymmetries often disappear. By avoiding artifacts that can lead to a misinterpretation of results, we may understand better how animals represent time. An alternative procedure for studying temporal discriminations is with the psychophysical bisection procedure in which following conditional discrimination training, intermediate durations are presented and the point of subjective equality is determined. Research using the bisection procedure has shown that pigeons represent temporal durations not only as their absolute value but also relative to durations from which they must be discriminated. Using this procedure, we have also found that time passes subjectively slower when animals are required to respond to the to-be-timed stimulus.

Section snippets

The instructional ambiguity hypothesis

The procedures that have been used to study memory for sample duration have involved two important elements. First, generally, the pigeons are trained in the absence of delays so delays are a novel experience for them. Second, and more important, the intertrial intervals are generally quite similar in appearance to the novel delays. Thus, the procedure may create for the pigeon a somewhat ambiguous condition. If the delay is mistaken for an intertrial interval, its appearance could be viewed as

Present–absent sample matching

In duration sample matching, when the short sample is 0-s long, the task becomes present–absent sample matching. In present–absent sample matching, on some trials there is a sample stimulus and on other trials the sample is absent. The sample may be a hue, a shape, or the presence of food (Grant, 1991, Maki, 1979, Sherburne and Zentall, 1993). It can even be the presence versus the absence of pecking two different sample stimuli (Weaver et al., 1999).

Present–absent sample matching bears some

Conclusions about artifacts

Research on memory for sample durations has been biased by an artifact produced by the similarity of the testing delays and the intertrial interval. This similarity of events is likely responsible for the divergent retention functions typically found (Sherburne et al., 1998). When the instructional ambiguity has been removed, parallel retention functions have been found. Furthermore, a second source of ambiguity may have been the novelty of the delays during testing. When delays were

Relational and subjective timing by pigeons

Recently, we have been interested in the degree to which timing by animals is affected by the context in which the animal is timing. One of the questions we have tried to answer is to what extent, in addition to their absolute values, the relational aspects of the short and long durations are encoded. A second question is how a secondary response requirement affects the animals’ timing ability.

Acknowledgements

The author thank Lou Sherburne, Tricia Clement, Rebecca Singer, Emily Klein, Daren Kaiser, Janice Weaver, and Brigette Dorrance for their contribution to the research presented in this article. Preparation of this article and much of the research described was supported by National Institute of Mental Health Grant MH-59194 and MH63726.

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