The effect of interstimulus interval on the discrimination of cryptic targets.

Abstract

In 4 experiments, pigeons were required to discriminate between the presence and absence of cryptic targets. Experiments compared performance when 1 stimulus type appeared in a session (run condition) with performance when 2 types appeared intermixed (mixed condition). When the interstnnulus interval (ISI) was short between successive presentations of the same stimulus, within-session improvements occurred in both run and mixed conditions (Experiments 1, 2, and 3). Experiment 4 showed that within-session improvements can occur as a result of mini-runs of 1 stimulus type followed by mini-runs of the other. These results suggest that several independent memory traces may be primed simultaneously and that performance is determined by the extent to which traces of stimuli have decayed by the time of their next presentation.The research reported here was supported by a grant from the United Kingdom Science and Engineering Research Council. I am very grateful to N. J. Mackintosh for his expert advice regarding these experiments and for his comments on a draft of this article.

Searching image in blue jays: Facilitation and interference in sequential priming

“…The direction ofthe effects of interstimulus interval was, however,opposite to that predicted by Plaisted's (1997) hypothesis. Although accuracy increased with increasing previous detections, as was observed in previous analyses (Figure SA),the main effect ofinterstimulus interval on response time resulted from a decrease in response time with longer intervals, not from the increase Plaisted would have predicted.…”

“…To estimate the effects of interstimulus interval (Blough, 1991;Plaisted, 1997) on accuracy and response time for positive trials. each positive trial was categorized by stimulus type and number of previous detections, as well as by the elapsed time since the offset of the last previous correctly detected trial of the same type.…”

“…Using pigeons searching for two distinctive checkerboard patterns, Plaisted found evidence that searching was facilitated by reducing the time since the last stimulus ofthe same type (the interstimulus interval) but that there were no interference effects when the two targets were presented in mixed blocks. Plaisted's (1997) demand for unequivocal evidence of interference may derive from an overly rigorous interpretation of the limited capacity model. Posner and Snyder (1975) found evidence that facilitation and interference effects are separate processes and are not symmetrical.…”

“…Blough (1989) coined the term sequential priming to refer to this technique for eliciting attentional search and has since conducted an extensive series of experiments in which the nature of the sequential priming effect is probed and contrasted with that of more conventional priming techniques (Blough, 1989(Blough, , 1991(Blough, , 1992Blough & Lacourse, 1994;Vreven & Blough, 1998). Plaisted (1997;Plaisted & Mackintosh, 1995) has recently challenged the attentional account of searching Copyright 1999 Psychonomic Society, Inc.…”

“…By manipulating the generative parameters for the background, we were able to control detectability with far greater precision than has ever been possible with naturalistic stimuli and to examine the effects of changes in both detectability and trial sequence. We employed a rigorous and fully counterbalanced design of sequentially primed and unprimed probe trials to test for interference effects, and, as a final analysis, we extracted a measure of interstimulus interval from our trial sequences and tested, to see whether it would provide a superior account of the sequential priming effect, as Plaisted's (1997) results would predict.…”