2 METHODS OF STIMULUS FADING APPLIED TO A SIMULTANEOUS FLICKER RATE DISCRIMINATION IN PIGEONS

Two commonly applied stimulus fading procedures were compared with a t rial-and-error procedure in their effect on error rates and rate of ac quisition of a difficult target discrimination. In the intensity fadin g procedure stimulus control by one pretrained dimension (color) was f aded 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 wa s then made progressively more difficult by gradually decreasing flick er rate differences, thus finally approaching the target discriminatio n. Only the transfer-along-a-continuum procedure facilitated the discr imination of the target discrimination relative to the trial-and-error control procedure, while the intensity fading procedure occasioned th e fewest errors during training. That is, acquisition and error rates were independent. The results are consistent with those in human appli ed situations in showing that fading improves the rate of learning onl y when it involves attentional shaping to the target stimulus dimensio n. (C) 1995 Academic Press, Inc.