Two methods of stimulus fading applied to a simultaneous flicker rate discrimination in pigeons

Abstract

Two commonly applied stimulus fading procedures were compared with a trial-and-error procedure in their effect on error rates and rate of acquisition of a difficult target discrimination. In the intensity fading procedure stimulus control by one pretrained dimension (color) was faded while combined with the new stimulus dimension (flicker rate) of the target discrimination. In the transfer-along-a-continuum procedure, an easy flicker-rate discrimination was presented initially which was then made progressively more difficult by gradually decreasing flicker rate differences, thus finally approaching the target discrimination. Only the transfer-along-a-continuum procedure facilitated the discrimination of the target discrimination relative to the trial-and-error control procedure, while the intensity fading procedure occasioned the fewest errors during training. That is, acquisition and error rates were independent. The results are consistent with those in human applied situations in showing that fading improves the rate of learning only when it involves attentional shaping to the target stimulus dimension.