Discriminations among perceptual and symbolic stimuli

This research compares the time required for perceptual discriminations among pairs of physically present objects (circles) with the time required to discriminate pairs of symbols Inonsense syllables) that subjects learned to associate uniquely with each of the circles. Four experiments show very large differences between symbolic and perceptual discriminations. Discrimination times for the perceptual stimuli declined systematically as their size ratio increased, but discriminations among the associated nonsense syllables showed only a strictly ordinal effect of position in the series. Discriminations among the symbolic stimuli showed a large semantic congruity effect, but the perceptual stimuli showed none. The research does not replicate previous results showing similarities between perceptual and symbolic processing suggestive of image processing. We conclude that in the symbolic task subjects use only ordinal information rather than images or analog representations of the associated circles. We propose that perceptual discriminations show a semantic congruity effect only when they are processed as if the perceptual stimuli were symbolic.     

Semantic congruity and lexical marking in symbolic comparisons: An expectancy hypothesis

Lexical marking and semantic congruity effects were investigated in four symbolic size comparison experiments. Predictions followed from an expectancy hypothesis suggested by results of recent comparative judgment studies. According to the present position, lexical marking and semantic congruity should be mutually exclusive effects in such tasks, and the demonstration of either dependent upon the order in which the stimuli and the comparative term are evaluated. When the comparative precedes the stimuli, an expectancy is created whereby the subject is more likely to be prepared for, say, large items following the comparative “larger” and small items following the comparative “smaller.” In addition, the usual advantage of unmarked as compared to marked comparisons should be offset by the initial processing of the comparative. As predicted, the comparative-stimulus presentation order produced a significant semantic congruity effect and no effect of lexical marking in Experiment 1. Conversely, when stimuli precede the comparative, or are presented simultaneously with it, no expectancy should be created, as the items are immediately available to the subject, and the semantic congruity effect should not be obtained. Upon presentation of the comparative, however, unmarked comparisons should be easier than marked comparisons. Experiments 2 and 4 confirmed these expectations, as significant lexical marking effects were obtained and significant congruity effects were not. These findings are contrary to predictions derived from a semantic coding interpretation of the symbolic comparison process.     

Semantic congruity effects in perceptual comparisons

Semantic congruity effects occur when, as in Experiment 1, for example, the time to select the shorter of two relatively short lines is faster than the time to select the longer; conversely, selection of the longer of two relatively long lines is faster than selection of the shorter. Semantic congruity effects are also demonstrated in experiments requiring comparisons of the heaviness of weights (Experiment 2) and horizontal extent (Experiment 3). In Experiment 1, the magnitude of the semantic congruity effect was larger under conditions emphasizing accuracy rather than speed and when the comparison was difficult. In fact, when comparisons were errorless, the effect was minimal (20 msec), thereby replicating previous failures to obtain the effect with supraliminal perceptual comparisons (Banks, Mermelstein, & Yu, 1982; Marschark & Paivio, 1981; Petrusic & Baranski, 1988a). In confirmation of Henmon's (1911) introspective analyses of psychophysical comparisons, Experiments 2 and 3 extend the range of the semantic congruity effect to include judgments of confidence. However, in each of the three experiments, semantic congruity effects were not evident with the response-accuracy measure. Finally, using highly confusable stimuli, in Experiment 3 the magnitude of the semantic congruity effect was shown to be larger for error than for correct response times. The implications of these findings for a decisional locus of the effect and for the semantic coding theory are discussed.     

Priming effects in perceptual classification

Priming stimuli that spatially flank a fixated target stimulus may cause either facilitation or interference with target classification, depending on experimental context. Two experiments demonstrated distinct effects of response compatibility and semantic congruity between flankers and target. Response competition occurred when targets were flanked by context stimuli associated with the opposite response, but this effect diminished when the target was delayed relative to the flankers. Facilitative priming by response-compatible flankers, in contrast, required prior exposure of the flankers, and was strongly influenced by the semantic congruity of flankers and targets. These differing time courses suggest that perceptual priming encompasses a variety of distinct underlying cognitive and motor events.     

Semantic congruity and expectancy in symbolic judgments

These experiments assess the degree to which the semantic-congruity effect in comparative judgment can be explained by such expectancy effects as priming, perceptual "set," or strategies used in the task. The first experiment mixed a lexical-decision task with the comparative-judgment task and showed that neither automatic semantic priming nor deliberate preparation can account for the congruity effect. Experiments 2-4 assessed expectancy effects in a different way by presenting the instructions for comparative judgment either before or after the pair to be judged. These experiments included, among other things, a number of safeguards against artifacts in this paradigm. In these three experiments the congruity effect was obtained with both orders of stimuli and instructions, contrary to the prediction of an expectancy hypothesis. The results indicate that when stimuli are not degraded. The semantic-congruity effect depends largely on the relation between the stimuli and the instructions and only to a small degree, if at all, on expectancy.     

Simple addition and multiplication: No comparison

Some models of memory for arithmetic facts (e.g., 5+2=7, 6×7=42) assume that only the max-left order is stored in memory (e.g., 5+2=7 is stored but not 2+5=7). These models further assume an initial comparison of the two operands so that either operand order (5+2 or 2+5) can be mapped to the common internal representation. We sought evidence of number comparison in simple addition and multiplication by manipulating size congruity. In number comparison tasks, performance costs occur when the physical and numerical size of numerals are incongruent (8 3) relative to when they are congruent (8 3). Sixty-four volunteers completed a number comparison task, an addition task, and a multiplication task with both size congruent and size incongruent stimuli. The comparison task demonstrated that our stimuli were capable of producing robust size congruity and split effects. In the addition and multiplication task, however, we were unable to detect any of the RT signatures of comparison or reordering processes despite ample statistical power: Specifically, there was no evidence of size congruity, split, or order effects in either the addition or multiplication data. We conclude that our participants did not routinely engage a comparison operation and did not consistently reorder the operands to a preferred orientation.     

Isolating the effects of symbolic distance,and semantic congruity in comparative judgments: An additive-factors analysis

The time needed to compare two symbols increases as the cognitive distance between them on the relevant dimension increases (symbolic distance effect). Furthermore, when subjects are told to choose either the larger or the smaller of two stimuli, the response time is shorter if the instruction is congruent with the overall size of the stimuli (semantic congruity effect). Three experiments were conducted to determine the locus of these effects in terms of a sequence of processing stages. The developmental aspects of these effects were also evaluated, as the subjects were from kindergarten, first grade, third grade, fifth grade, and college. By varying the visual quality of the stimulus in each experiment, it was determined that the distance effect resides in a comparison stage, whereas the congruity effect is an encoding phenomenon. Both distance and congruity effects were present at all grade levels, but they decreased in magnitude as grade increased. The results were interpreted relative to recent models of comparative judgments.     

Toward a unified account of spacing effects in explicit cued-memory tasks

Memory for repeated items improves when presentations are spaced during study. This effect is found in memory tasks using different types of material, paradigms, and participant populations. Although several explanations have been proposed, none explains the presence of spacing effects in cued-memory tasks for unfamiliar stimuli. Two experiments assessed the spacing effect on a yes-no recognition-memory task using nonwords and words as targets. The main results showed that changing the font between repeated occurrences of targets at study removed the spacing effect for nonwords only. A 3rd experiment using lexical decision showed that the font manipulation reduced repetition priming of nonwords when items were repeated at Lag 0. These results suggest that short-term perceptual priming supports spacing effects in cued-memory tasks for unfamiliar stimuli.     

Competition between memory and perceptual tasks involving physically similar stimuli

Performance on a perceptual recognition task and a concurrently performed short-term memory (STM) task was studied. The stimuli used in the STM task were either visually similar, acoustically similar, or dissimilar to the stimuli in the perceptual task. The results demonstrated that any type of concurrent list memorization has a detrimental effect upon perceptual performance, but this effect is magnified if the stimuli used in the 2 tasks are visually similar. Acoustic similarity had no effect. The results document the fact that distinct tasks interfere, when the tasks compete for a limited total processing capacity, or when the tasks demand the same visual coding program.     

Semantic congruity in symbolic comparisons: Evidence against an expectancy hypothesis

A previously proposed expectancy hypothesis predicts that the semantic congruity effect typically observed in symbolic comparison tasks will be eliminated when the items to be compared are presented prior to the comparative. Previous studies testing this hypothesis have been inconclusive. The present experiments demonstrate that a semantic congruity effect can be obtained when the comparative follows the pair after a 1-sec (Experiment 1) or 4-sec (Experiment 2) delay. Lexical markedness effects were also obtained. The key to producing a “comparative-after” congruity effect is to intermix questions about several different dimensions, so that when the pair is presented, subjects will be unable to anticipate the question. The results disconfirm the expectancy hypothesis.     

Simultaneous auditory and tactile information processing

Subjects were required to perform perceptual tasks when stimuli were presented simultaneously in the auditory and tactile modalities and when they were presented in one of the modalities alone. The results indicated that when the demands on cognitive processes are small, auditory and tactile stimuli presented simultaneously can be processed as well as when stimuli are presented in only one modality. In a task which required a large amount of cognitive processing, it became difficult for subjects to maintain high levels of performance in both modalities and the distribution of attention became an important determinant of performance. The data were consistent with a theory that cognitive, but not perceptual, processing is disrupted when subjects have difficulty performing two perceptual tasks simultaneously.     

The psychophysics of numerical comparison: a reexamination of apparently incompatible data

Reaction-time studies of numerical comparison have used essentially two paradigms: classification, in which a target number must be labelled "larger" or "smaller" in comparison to a fixed standard, and selection, in which the larger (or smaller) number of a pair must be picked out. In previous studies, classification has yielded only a distance effect in RTs, whereas selection has also revealed magnitude (or minimum) and congruity effects. We used two experiments with two-digit number comparisons to find the reason for this discrepancy. In Experiment 1, we used a variant of the classification task with the standard changing on each trial. RTs increased along with the standard for "smaller" responses and decreased along with the standard for "larger" responses, in a manner reminiscent of magnitude and congruity effects. In Experiment 2, we again used classification, but the fixed standard 75 was not at the center of the range of target numbers (20, 21, ... 99). Close to the standard, RTs were faster for "larger" than for "smaller" responses, again a congruity effect. Our data show that magnitude and congruity effects can be obtained with two-digit numbers in classification as well as in selection tasks. A single equation, which implies that numbers are compared with respect to reference points at both ends of the continuum, describes the results from both tasks.     

Contextual influences on interactive processing: Effects of discriminability,quantity, and uncertainty

Three contextual factors—(1) the discriminability of stimuli in pitch, (2) the number of stimuli differing in pitch, and (3)the uncertainty regarding which stimuli or tasks would appear—were manipulated as subjects performed speeded loudness classifications in each of six experiments. The magnitude of Garner interference and effects of congruity were used to gauge the degree of interactive processing. Enhancing pitch discriminability caused monotonic increases in interference and congruity. Stimulus-task uncertainty mediated the changes in Garner interference wrought by increased discriminability. Uncertainty also caused a surprising shift in congruity from strongly positive to strongly negative as uncertainty grew. Increasing stimulus quantity lowered interference, but had inconsistent effects on congruity. Regression analyses suggested that, collectively, these three contextual variables underlie most failures of selective attention in speeded classification.     

A memory-based account of automatic numerosity processing

We investigated the mechanisms responsible for the automatic processing of the numerosities represented by digits in the size congruity effect (Henik & Tzelgov, 1982). The algorithmic model assumes that relational comparisons of digit magnitudes (e.g., larger than {8,2}) create this effect. If so, congruity effects ought to require two digits. Memory-based models assume that associations between individual digits and the attributes "small" and "large" create this effect. If so, congruity effects ought only to require one digit. Contrary to the algorithmic model and consistent with memory-based models, congruity effects were just as large when subjects judged the relative physical sizes of small digits paired with letters as when they judged the relative physical sizes of two digits. This finding suggests that size congruity effects can be produced without comparison algorithms.     

Repetition advantage and disadvantage in perceptual identification tasks

Repetitive presentation of a stimulus brings not only advantage but also disadvantage when performing perceptual identification tasks. In this study, the conflicting phenomena of the effect of repetition were examined using two Kana character sets (Hiragana and Katakana) as stimuli. Two identical or different stimuli were presented in rapid succession and participants were asked to identify and report them. The stimulus onset asynchrony (SOA) between the two stimuli was varied from 200 ms to 1200 ms, according to which the suitable temporal conditions for the two distinct effects of repetition were explored. The results indicated that two distinct effects of repetition occurred depending on the informational code shared by the two stimuli. An interference effect of repetition was observed with SOA values of up to 500 ms when the two stimuli were identical in terms of their visual pattern code (Hiragana), whereas a superior effect of repetition was observed with an SOA value of 200 ms when they were identical only in terms of their phonological code (Hiragana and Katakana). From these findings, the author proposes that when two identical stimuli are presented in rapid succession, inhibition and activation mechanisms may function at different levels of processing.     

Semantic congruity in symbolic comparisons: Salience,expectancy, and associative priming

An expectancy interpretation of semantic congruity effects suggests that in symbolic comparisons involving the typical comparative-then-stimuli paradigm, the comparative acts as a cue in priming memory for related stimuli. A recent study by Holyoak and Mah (1981) presented evidence purported to disconfirm this hypothesis insofar as a congruity effect also was obtained when the stimuli preceded the comparative. The present study showed the stimulicomparative effect to be a consequence of the pairing of stimuli with particularly salient comparatives such that the former could serve the cuing function. This finding is consistent with the expectancy hypothesis in emphasizing the role of a flexible encoding process but inconsistent with the view that only comparatives can create expectancies in symbolic comparisons.     

Response-mediated spatial priming despite perfectly valid target location cues and intervening response events

Attentional effects are often inferred from keypress reaction time (RT) studies when two sequentially presented stimuli, appearing at the same location, generate costs or benefits. The universality of these attentional attributions is challenged by data from perceptual discrimination tasks, which reveal that location repetition benefits and costs depend on whether a prior response repeats or switches, respectively. According to dual-stage accounts, these post-attentional effects may be abolished by making responses in between two target stimuli or by increasing target location certainty, leaving only attentional effects. Here, we test these accounts by requiring responses to stimuli in between targets and by increasing target location certainty with 100% valid location cues. Contrary to expectations, there was no discernible effect of cueing on any repetition effects, although the intervening response diminished stimulus-response repetition effects while subtly reducing location-response repetition effects. Despite this, there was little unambiguous evidence of attentional effects independent of responding. Taken together, the results further highlight the robustness of location-response repetition effects in perceptual discrimination tasks, which challenge whether there are enduring attentional effects in this paradigm.     

Dimensional interaction between color and pitch

In three experiments I investigated the nature of cross-modal dimensional interaction by testing speeded classification of the synesthetically corresponding dimensions of color (white-black) and pitch (high-low). Experiment 1 showed significant Garner interference when these dimensions were varied orthogonally--redundancy gain for positively correlated dimensions and redundancy loss for negatively correlated dimensions. Attributes from synesthetically congruent stimuli were classified faster than attributes from incongruent stimuli (a congruity effect). Experiment 2 tested a perceptual explanation of this interaction (i.e., that color and pitch are configural dimensions) by using Pomerantz's (1986) diagnostic (comparison of selective and divided attention performance). The configurality hypothesis received little support. Experiment 3 examined the effect of optional processes on color and pitch classification. The results suggest that partly strategic and partly mandatory components may constitute overall performance. Three alternative explanations of the color-pitch interaction--perceptual, semantic, and response based--are evaluated in the context of the present results.     

Holistic vs. attribute repetition effects in classifying stimuli

The effect of the just previous stimulus on the current response was determined in three speeded classification experiments. When the stimuli were perceptual patterns, and when they were words, there was marked facilitation if the previous stimulus was identical to the current stimulus. When successive perceptual stimuli were composed of identical elements, but in a changed configuration, there was no measureable sequential effect on “same” response times. These results are for integral stimuli. When stimuli are not integral, as with some studies in the literature, it is suggested that each two-dimensional nonintegral stimulus is treated by the observer as two objects. In those cases, responses can be facilitated by repetition of that object on which responses were based on the previous trial, and this can occur when a value of the other dimensions (other objects) has not repeated. Accordingly, the processing of integral and nonintegral stimuli must be considered separately when attempting to evaluate process models. Further, facilitation due to stimulus repetitions does not account for all of the differences in response times between various classification tasks. These additional differences may be attributed to a multidimensional range effect analogous to the range effects found in psychophysical tasks.     

Sequential analysis of the numerical Stroop effect reveals response suppression

Automatic processing of irrelevant stimulus dimensions has been demonstrated in a variety of tasks. Previous studies have shown that conflict between relevant and irrelevant dimensions can be reduced when a feature of the irrelevant dimension is repeated. The specific level at which the automatic process is suppressed (e.g., perceptual repetition, response repetition), however, is less understood. In the current experiment we used the numerical Stroop paradigm, in which the processing of irrelevant numerical values of 2 digits interferes with the processing of their physical size, to pinpoint the precise level of the suppression. Using a sequential analysis, we dissociated perceptual repetition from response repetition of the relevant and irrelevant dimension. Our analyses of reaction times, error rates, and diffusion modeling revealed that the congruity effect is significantly reduced or even absent when the response sequence of the irrelevant dimension, rather than the numerical value or the physical size, is repeated. These results suggest that automatic activation of the irrelevant dimension is suppressed at the response level. The current results shed light on the level of interaction between numerical magnitude and physical size as well as the effect of variability of responses and stimuli on automatic processing.