Reaction times and error rates for “same”-“different” judgments of multidimensional stimull

Abstract

Suppose S is presented, either simultaneously or successively, with two multidimensional stimuli and is asked to judge whether the two stimuli are "same" or "different." Egeth (1966) has outlined a number of plausible models showing how S might perform this task. The discussion that follows is similar to his analysis.A stimulus dimension will be said to be either "same" or "different" depending on whether or not the two stimuli match each other along that dimension. The act of comparing two stimuli along a given dimension and, thus, deciding if that dimension is "same" or "differen t" may be termed processing that dimension.Since the stimuli are multidimensional, S must process a number of dimensions in order to decide whether the stimuli are "same" or "different." Would S process these dimensions one at a time, one after another? Or might they all be processed simultaneously? Models of S's performance that assume the former may be called serial (process) models, while those that assume the latter may be called parallel (process) models. In the case of parallel models, even though the processing of each dimension is begun simultaneously with the other dimensions, it need not be finished simultaneously with the other dimensions.When the two stimuli are "same," S must process all relevant dimensions in order to be sure that the stimuli are "same." What about the occasions when the two stimuli are "different"? As soon as S has finished processing any "different" dimension, he has enough information to decide that the stimuli are "different." Will he conclude at that point that the stimuli are "different," or will he wait until processing has been finished on all dimensions before making a decision? Models that assume the former may be called self-terminating (process) models, while those that assume the latter may be called exhaustive (process) models.This analysis has generated four types of models. There are serial and parallel models and within each of these types there are both self-terminating and exhaustive models.The reaction times (RT) of S's judgments provide a means of testing these models. Suppose that S is asked to make one of two responses depending on whether the two stimuli are "same" or "different." One question of interest is: How does the mean RT of the "same" response compare with the mean RT of the "different" response?On a certain subset of trials, the two stimuli differ along exactly D stimulus dimensions. Suppose that the D dimensions that are to be "different" are chosen randomly on each trial. Another question of interest is: How does the mean RT of the "different" response vary as a function of D, the number of "different" dimensions?The term processing isochronality will indicate that, for each stimulus dimension, the processing time for that dimension is independent of whether the dimension is "same" or "different." Similarly, the term efferent isochronality will indicate that the amount of time intervening between the decision to respond and the completion of the response is independent...

Perceptual processing of adjacent and nonadjacent tactile nontargets

“…The responses for these two trial types were the same; only the stimuli were different. In this sense, the finding parallels that reported by a number of investigators that "same" responses to identical stimuli are typically more accurate and faster than correct "different" responses (Bamber, 1969;Krueger, 1970Krueger, , 1978Nickerson, 1965;Proctor, 1981). A number of explanations of the fast "same" effect have been advanced in the literature.…”

Visual comparison of words and random letter strings: Effects of number and position of letters different

“…However, an important recent development has been the demonstration that in "same-different" judgments "same" RTs are consistently faster than this model predicts. This finding has suggested to a number of theorists (see Nickerson, 1972) that "same" decisions are based on a wholistic matching process which, up to some capacity limit (Silverman, 1973), is less sensitive to the number of critical features in the display (Bamber, 1969;Beller, 1970). Such dual-process interpretations have received further support from studies reporting manipulations which affect "same" and "different" RTs selectively (Krueger, 1970(Krueger, , 1973Egeth & Blecker, 1971).…”

Isolating visual units in the perception of words and nonwords

“…There is no generally accepted explanation for this result, but it is frequently proposed that same and different decisions are mediated by different processes (e.g., Bamber, 1969 Because of the marginally significant differences in RT trends and the large differences in error rates between same and different decisions, the RT data for the two decision types were submitted to separate analyses of variance. Both were two-factor, withinsubjects designs, with the factors being Stimulus Type and Alternation Condition.…”