ACQUISITION OF DELAYED MATCHING IN THE PIGEON¹

Abstract

Pigeons were exposed to three successive matching-to-sample procedures. On a given trial, the sample (red, green or blue light) appeared on a center key; observing responses to this key produced the comparison stimuli on two side keys. Seven different experimental conditions could govern the temporal relations between the sample and comparison stimuli. In the "simultaneous" condition, the center key response was followed immediately by illumination of the side key comparison stimuli, with the center key remaining on. In "zero delay" the center key response simultaneously turned the side keys on and the center key off, while in the "variable delay" conditions, intervals of 1, 2, 4, 10, and 24 sec were interposed between the offset of the sample and the appearance of the comparison stimuli on the side keys. In all conditions, a response to the side key of matching hue produced reinforcement, while a response to the non-matching side key was followed by a blackout. In procedure I all seven experimental conditions were presented in randomly permutated order. After nine sessions of exposure (at 191 trials per session, for a total of 1719 trials) the birds gave no evidence of acquisition in any of the conditions. They were therefore transferred to Procedure II, which required them to match only in the "simultaneous" condition, with both the sample and comparison stimuli present at the same time. With the exception of one bird, all subjects acquired this performance to near 100% levels. Next, in Procedure III, they were once more exposed to presentation of all seven experimental conditions in random order. In contrast to Procedure I, they now acquired the delay performance, and were able to match effectively at delays of about 4 sec.

Animal memory: The contribution of generalization decrement to delayed conditional discrimination retention functions

“…The implication of this finding is that the typical procedure for assessing retention functions overestimates the amount of forgetting, because it includes a generalization decrement unrelated to the animal's loss of memory (White, 2001). Consistent with the hypothesis that at least some of the loss of matching accuracy that accompanies the introduction of delays can be attributed to a generalization decrement, pigeons generally show improved matching accuracy with added experience with delays (e.g., Berryman et al, 1963;Grant, 1976;Roberts & Grant, 1976).…”

“…Once matching accuracy reaches a high level, a delay that varies in duration from trial to trial is inserted between the offset of the sample and the onset of the comparison stimuli, allowing one to plot a retention function of matching accuracy as a function of delay (Blough, 1959;Clement & Zentall, 2000;Grant, 1975Grant, , 1981Grant & Roberts, 1973;Roberts, 1972Roberts, , 1974Santi & Hope, 2001;Santi, Lellwitz, & Gagne, 2006;Singer, Klein, & Zentall, 2006;Zentall, Hogan, Howard, & Moore, 1978; see also a similar procedure in delayed matching research with monkeys in Eacott, Gaffan, & Murray, 1994). One reason that investigators have typically trained with a 0-sec delay prior to testing with longer delays may be, as Berryman, Cumming, and Nevin (1963) reported, that pigeons exposed to delays from the start of matching training failed to acquire the matching task.…”

“…There has been little challenge to the basic methodology involving training with no delay and introducing delays following acquisition, which has remained in use for almost 50 years (see Berryman et al, 1963). The problem with the basic methodology is that the novelty of the y delays may result in a decrement in matching accuracy d (i.e., a generalization decrement) that cannot be attributed to sample forgetting (see Zentall, 1997).…”

“…The problem with the basic methodology is that the novelty of the y delays may result in a decrement in matching accuracy d (i.e., a generalization decrement) that cannot be attributed to sample forgetting (see Zentall, 1997). The fact that pigeons often perform the conditional discrimination at levels close to chance (50%) with delays as short as 5-10 sec (Berryman et al, 1963;Grant & Roberts, 1973;Zentall & Hogan, 1977) suggests the possibility that such retention functions may not accurately represent the pigeon's ability to remember the sample.…”

Simple discrimination training and conditional discrimination response

“…Further, the acquisition speed difference reported in the literature was not observed (Berryman, Cumming & Nevin, 1963;Cumming & Berryman, 1965; for example), maybe because the delay between sample stimulus disappearance and the comparisons appearance was very short.…”