Repetition effects in choice reaction time to multidimensional stimuli

Ss classified as quickly as possible stimuli back-projected one at a time on a small screen by pressing one of two levers in response to each stimulus, according to the levels of a single specified binary stimulus dimension. Stimuli were rectangles varying in height alone, in width alone, or in both dimensions, in either a correlated or an orthogonal fashion. Stimuli followed responses by a fixed interval of 82, 580, or 1,080 msec. Response time was longer when both dimensions varied orthogonally than when only one dimension varied, indicating that Ss were unable to avoid perceiving the rectangle figures as wholes. Repeated stimuli were responded to more quickly than stimuli which were different from the immediately preceding stimulus in all conditions. With orthogonally combined dimensions, response time to stimulus repetitions was lowest, increased when the stimulus changed while the response was repeated, and increased still further when both the stimulus and the response changed. Increasing the time interval between stimuli decreased response time for nonrepetitions, while response time for repetitions was relatively unaffected. The results were discussed in terms of two models of serial choice reaction time.     

Parallel processing in complex visual discrimination

In a “same-different” reaction time (RT) task pairs of stimuli varying along one or more dimensions are presented and S is required to indicate, as rapidly as possible, whether the stimuli are physically identical or different. This task was employed in three experiments investigating the processes by which multidimensional stimuli are discriminated. The results indicated that stimulus dimensions are compared in parallel; that the time required to interrogate a dimension varies randomly across trials and is dependent upon the time required to interrogate other dimensions present in test stimuli, and that comparisons terminate upon the detection of information sufficient for a correct response.     

Does right-left prevalence occur for the Simon effect?

In four experiments, we investigated whether a right-left prevalence effect occurs for the Simon task, in which stimulus location is irrelevant, when the stimulus and the response sets vary along horizontal and vertical dimensions simultaneously. Simon effects were evident for both dimensions, and they were of similar magnitude, indicating no prevalence effect. Manipulations of the relative salience of the dimensions for the stimulus and the response sets resulted in a larger Simon effect for the more salient dimension than for the less salient one, but there was no overall prevalence effect. The results indicate that manipulations of salience affect the relative magnitudes of automatic response activation for the vertical and the horizontal dimensions but that the right-left prevalence effect is due to a coding bias in intentional response selection processes when stimulus location is relevant.     

Determinants of right-left and top-bottom prevalence for two-dimensional spatial compatibility

When stimulus and response sets vary along horizontal and vertical dimensions, the horizontal dimension is more dominant than the vertical one, an effect called right-left prevalence. Three accounts have been proposed that attribute the effect to a reduced ability to code vertical locations when horizontal codes are also present, the use of right-left effectors, or a difference in salience of the 2 dimensions. The accounts differ in terms of whether the ability to code and process the 2 dimensions is of limited capacity and whether the prevalence effect is a consequence of the effectors used for responding. The authors report 4 experiments that evaluated these issues. Results indicate that use of right-left effectors is important to the right-left prevalence effect because it increases the salience of the horizontal dimension. However, a top-bottom prevalence effect can be obtained if the vertical dimension is made more salient.     

Stimulus-set location does not affect orthogonal stimulus-response compatibility

In two-choice tasks for which stimuli and responses vary along orthogonal dimensions, one stimulus-response mapping typically yields better performance than another. For unimanual movement responses, the hand used to respond, hand posture (prone or supine), and response eccentricity influence this orthogonal stimulus-response compatibility (SRC) effect. All accounts of these phenomena attribute them to response-related processes. Two experiments examined whether manipulation of stimulus-set position along the dimension on which the stimuli varied influences orthogonal SRC in a manner similar to the way that response location does. The experiments differed in whether the stimulus dimension was vertical and the response dimension horizontal, or vice versa. In both experiments, an advantage of mapping up with right and down with left was evident for several response modes, and stimulus-set position had no influence on the orthogonal SRC effect. The lack of effect of stimulus-set position is in agreement with the emphasis that present accounts place on response-related processes. We favor a multiple asymmetric codes account, for which the present findings imply that the polarity of stimulus codes does not vary across task contexts although the polarity of response codes does.     

No overall right-left prevalence for horizontal and vertical Simon effects

The present study confirmed that there is no overall right-left prevalence effect for Simon tasks, in which stimulus location is irrelevant, when (1) the stimulus and response sets vary along both horizontal and vertical dimensions simultaneously, (2) the stimulus set varies along both dimensions, but the response set varies along only one dimension, and (3) the stimuli and responses vary in one of four possible locations and responses are made by a unimanual joystick movement. In all experiments, Simon effects of similar magnitude were evident for both the horizontal and the vertical dimensions. The findings suggest that the right-left prevalence effect observed with two-dimensional location-relevant tasks is not due to stronger overall automatic activation of horizontal codes but to different translation efficiencies in intentional response selection processes.     

No overall right-left prevalence for horizontal

The present study confirmed that there is no overall right—left prevalence effect for Simon tasks, in which stimulus location is irrelevant, when (1) the stimulus and response sets vary along both horizontal and vertical dimensions simultaneously, (2) the stimulus set varies along both dimensions, but the response set varies along only one dimension, and (3) the stimuli and responses vary in one of four possible locations and responses are made by a unimanual joystick movement. In all experiments, Simon effects of similar magnitude were evident for both the horizontal and the vertical dimensions. The findings suggest that the right—left prevalence effect observed with two-dimensional location-relevant tasks is not due to stronger overall automatic activation of horizontal codes but to different translation efficiencies in intentional response selection processes.     

Parallel processing of the attributes of single stimuli

Three experiments are described, in which Ss had to decide whether or not single stimuli, varying along the dimensions of shape and color, satisfied a given criterion. In different conditions, the number of dimensions relevant to the criterion was varied. The first experiment indicates that simple interpretations of a standard Nickerson procedure are potentially artifactual. In the last two experiments, a design involving different difficulties of discrimination was used so that a serial interpretation of the results could be convincingly rejected, even for unpracticed Ss. These results strongly support the view that perceptually parallel processing normally occurs in the identification of single multidimensional stimuli. By this interpretation, apparently similar tasks may produce different patterns of results because of the use of different decision processes by the Ss.     

Spatial Repetition Blindness Is Modulated by Selective Attention to Color or Shape

Subjects reported either the colors or shapes of two simultaneous masked letters. Our first study found that they were less accurate when the reported features were identical ("repetition blindness," or RB), while repetition along the unreported dimension had no effect. Three follow-up studies confirmed that when the same dimension was judged (overtly or covertly) for both stimuli, performance was only affected by repetition along that dimension. However, when different dimensions were judged for the two stimuli, performance was affected by repetition on both dimensions. These findings support new conclusions about both RB and visual attention. First, RB depends critically on visual attention, rather than simply on the stimulus presented or the overt response required. Second, while attention can be restricted to a single visual dimension, this is efficient only when the same dimension is selected for both objects. Selecting the color of one object and the shape of another simultaneous object results in both dimensions being accessed for both objects.     

Informational primacy of visual dimensions: Specialized roles for luminance and chromaticity in figure-ground perception

Three experiments were conducted to examine the distinct contributions of two visual dimensions to figure-ground segregation. In each experiment, pattern identification was assessed by asking observers to judge whether a near-threshold test pattern was the same or different in shape to a high-contrast comparison pattern. A test pattern could differ from its background along one dimension, either luminance (luminance tasks) or chromaticity (chromaticity tasks). In each task, performance in a baseline condition, in which the test pattern was intact, was compared with performance in each of several degradation conditions, in which either the contour or the surface of the figure was degraded, using either partial occlusion (Experiment 1) or ramping (Experiments 2 and 3) of figure-ground differences. In each experiment, performance in luminance tasks was worst when the contour was degraded, whereas performance in chromaticity tasks was worst when the surface was degraded. This interaction was found even when spatial frequencies were fixed across test patterns by low-pass filtering. The results are consistent with a late (postfiltering) dual-mechanism system that processes luminance information to extract boundary representations and chromaticity information to extract surface representations.     

Informational primacy of visual dimensions: specialized roles for luminance and chromaticity in figure-ground perception

Three experiments were conducted to examine the distinct contributions of two visual dimensions to figure-ground segregation. In each experiment, pattern identification was assessed by asking observers to judge whether a near-threshold test pattern was the same or different in shape to a high-contrast comparison pattern. A test pattern could differ from its background along one dimension, either luminance (luminance tasks) or chromaticity (chromaticity tasks). In each task, performance in a baseline condition, in which the test pattern was intact, was compared with performance in each of several degradation conditions, in which either the contour or the surface of the figure was degraded, using either partial occlusion (Experiment 1) or ramping (Experiments 2 and 3) of figure-ground differences. In each experiment, performance in luminance tasks was worst when the contour was degraded, whereas performance in chromaticity tasks was worst when the surface was degraded. This interaction was found even when spatial frequencies were fixed across test patterns by low-pass filtering. The results are consistent with a late (postfiltering) dual-mechanism system that processes luminance information to extract boundary representations and chromaticity information to extract surface representations.     

Single linear ordering versus multiple discrepant orderings in the cognitive representation of social structures

Previous studies have assumed that people have a predilection for single linear orderings, of which status congruence is a special case. Eighty-two subjects were run in a two-stage experiment to examine preference for linear orderings and whether single or multiple discrepant orderings are preferred when 1 instead of having to learn, subjects freely construct social structures, and 2 the material they are presented is more specified and less simplified than is usually the case in cognitive bias studies. In the first stage Ss were presented with sets of five individual characteristic dimensions, of which three were inherently orderable. Their task was to attribute one characteristic from each dimension to each of five fictitious persons. In the second stage, Ss were asked, for three types of influence (professional, political and cultural), to build an influence structure among the five persons constructed in the first stage. In Stage 1, linear ordering was used for three of the five dimensions. Two of these dimensions used a single ordering, while the third was only weakly related to the first two. In Stage 2, largely transitive but incomplete relations of influence were established, based on a salary-occupational hierarchy. The completeness of the relation depended on the nature of the influence.     

Influence of auditory and audiovisual stimuli on the right–left prevalence effect

When auditory stimuli are used in two-dimensional spatial compatibility tasks, where the stimulus and response configurations vary along the horizontal and vertical dimensions simultaneously, a right–left prevalence effect occurs in which horizontal compatibility dominates over vertical compatibility. The right–left prevalence effects obtained with auditory stimuli are typically larger than that obtained with visual stimuli even though less attention should be demanded from the horizontal dimension in auditory processing. In the present study, we examined whether auditory or visual dominance occurs when the two-dimensional stimuli are audiovisual, as well as whether there will be cross-modal facilitation of response selection for the horizontal and vertical dimensions. We also examined whether there is an additional benefit of adding a pitch dimension to the auditory stimulus to facilitate vertical coding through use of the spatial-musical association of response codes (SMARC) effect, where pitch is coded in terms of height in space. In Experiment 1, we found a larger right–left prevalence effect for unimodal auditory than visual stimuli. Neutral, non-pitch coded, audiovisual stimuli did not result in cross-modal facilitation, but did show evidence of visual dominance. The right–left prevalence effect was eliminated in the presence of SMARC audiovisual stimuli, but the effect influenced horizontal rather than vertical coding. Experiment 2 showed that the influence of the pitch dimension was not in terms of influencing response selection on a trial-to-trial basis, but in terms of altering the salience of the task environment. Taken together, these findings indicate that in the absence of salient vertical cues, auditory and audiovisual stimuli tend to be coded along the horizontal dimension and vision tends to dominate audition in this two-dimensional spatial stimulus–response task.     

The influence of irrelevant information on speeded classification tasks

Multidimensional stimuli, which could vary on one, two, or all three dimensions within a particular series, were presented to Ss who were required to classify each stimulus on the basis of its value on a specified dimension. The prior relevance of the irrelevant dimensions and the difficulty of the task were varied. Latency and error data indicated that Ss were unable to gate the irrelevant information effectively. It was further concluded that this lack of perfect gating cannot be simply attributed to competing responses learned during the experiment.     

Attitudinal maintenance of cognitive categorization

Two experiments were performed that investigated attitudinal influences on cognitive categorization. The studies assessed categorization as a dynamic process with a multiple-sort (MS) technique, having Ss recategorize sentences unti! they ran out of meaningful categories. Condition I allowed Ss to use any dimensions they chose, and Condition It imposed the restraint of the “favorable-unfavorable” dimension. No effects of involvement were found when unrestricted sorting was allowed but were found when the evaluative dimension was imposed. There appeared to be a tendency for attitudinal involvement to maintain complexity across sorts. Results were discussed in terms of the influence of dimensions and the possible effects of certain stimulus properties on the maintenance of categorization complexity.     

Integral processing of visual place and auditory voicing information during phonetic perception.

Results of auditory speech experiments show that reaction times (RTs) for place classification in a test condition in which stimuli vary along the dimensions of both place and voicing are longer than RTs in a control condition in which stimuli vary only in place. Similar results are obtained when subjects are asked to classify the stimuli along the voicing dimension. By taking advantage of the "McGurk" effect (McGurk & MacDonald, 1976), the present study investigated whether a similar pattern of interference extends to situations in which variation along the place dimension occurs in the visual modality. The results showed that RTs for classifying phonetic features in the test condition were significantly longer than in the control condition for the place and voicing dimensions. These results indicate a mutual and symmetric interference exists in the classification of the two dimensions, even when the variation along the dimensions occurs in separate modalities.     

Intentionality and meta-awareness of mind wandering: Are they one and the same,or distinct dimensions?

Researchers have recently demonstrated that mind-wandering episodes can vary on numerous dimensions, and it has been suggested that assessing these dimensions will play an important role in our understanding of mind wandering. One dimension that has received considerable attention in recent work is the intentionality of mind wandering. Although it has been claimed that indexing the intentionality of mind wandering will be necessary if researchers are to obtain a coherent understanding of the wandering mind, one concern is that this dimension might be redundant with another, longstanding, dimension: namely, meta-awareness. Thus, the utility of the argument for assessing intentionality rests upon a demonstration that this dimension is distinct from the meta-awareness dimension. To shed light on this issue, across two studies we compared and contrasted these dimensions to determine whether they are redundant or distinct. In both studies, we found support for the view that these dimensions are distinct.     

The effects of sequential presentation and spatial arrangements on the free classification of multidimensional stimuli

Subjects classified sets of eight stimuli, constructed from three binary dimensions, into discrete groups in any way they wished. The stimuli were presented either simultaneously (all atonce) or sequentially (one at a time). When stimuli were presented simultaneously, different spatial arrangements did not produce different classifications. When stimuli were presented sequentially, in some sequential orders the level of each dimension varied at a different position in the sequence. For these orders, Ss tended to use the two levels of the first dimension that varied to classify the stimuli into two groups. But, other orders in which the levels of all dimensions varied on the second stimulus did not influence Ss’ classification. A comparison of sequential and simultaneous presentation showed for sequential presentation: (a) a smaller number of classifications was made using the dimensional structure to classify the stimuli, and (b)of those classifications that were dimensional, fewer dimensions were used to classify the stimuli into groups.     

Behavioral Goals Constrain the Selection of Visual Information

Although there is agreement that attentional processes are limited, the necessary conditions for such limitation have not been determined. We investigated whether behavioral goals are sufficient to constrain the selection of visual information. In two tasks, subjects were presented with targets and distractors that varied on two dimensions (e.g., color and letter). In separate conditions, the subjects' goal was to identify only one dimension of the target while ignoring the second dimension and ignoring the distractors. In both tasks, peripheral distractors interfered with target selection only when the targets and distractors differed on the goal-relevant dimension. When the goal was changed, the pattern of interference from the same stimuli was reversed, so that distractors affected target selection only according to the new goal. These results suggest that behavioral goals constrain the selection of visual information to a greater extent than the physical characteristics of the visual information.     

Intrusion patterns in rapid serial visual presentation tasks with two response dimensions

A rapid serial visual presentation (RSVP) paradigm using both one and two response dimensions was used to test parallel processing models of stimulus dimensions. Fifty subjects were asked to report the identity and/or color of a target uppercase word inserted in a series of lowercase words. The results produced a predominance of posttarget intrusions for color responses and a predominance of pretarget intrusions for identity responses. The requirement of a response to a second dimension impaired hit rates but did not change the pattern of intrusions. An examination of the distributions of intrusions in each response dimension as a function of the response given to the other dimension showed an unexpectedly high percentage of simultaneous hits, a moderate covariation between both responses, and the same patterns of intrusions when compared with the general distributions. While these results seem to be compatible with parallel models of processing for stimulus dimensions, two modifications to this model are suggested. First, the processing of response dimension(s) needs some attentional resources. Second, provision for a mixed model is indicated, which would include trials where no illusory conjunctions are formed.