Weavers, R., Foster, T. M., & Temple, W. (1998). Reinforcer efficacy in a delayed matching-to-sample task. Journal of the Experimental Analysis of Behavior, 69, 77-85.

Five domestic hens were exposed to a delayed matching-to-sample task. Conditions 1, 5, and 8 were variable-delay conditions in which five delays (0.25, 1, 2, 4, and 8 s) from the red or green sample to the presentation of the red and green comparison stimuli were presented a number of times during each session. In the fixed-delay condition (Condition 3), each delay was presented for 15 sessions under a Latin square design across birds. When improvements in accuracy across the variable-delay conditions are taken into account, the data were similar under both the variable and fixed delays. In Conditions 2, 4, 6, and 7 sample—reinforcer intervals were held at 8, 8, 4, and 2 s, respectively, while sample—choice intervals were varied within these during each session. With increasing sample—reinforcer interval, both initial discriminability (i.e., with sample—choice delay = 0) and rate of decrement in discriminability decreased. Although the former would be predicted if accuracy depends of the average sample—reinforcer interval, the latter would not. These data show that increasing the sample—choice interval had less effect on matching accuracy than increasing the sample—reinforcer interval did.

Key words: delayed matching to sample, variable delay, fixed delay, sample—reinforcer interval, direct remembering, key peck, hens