The purpose of this paper is to investigate the effect of irrelevant location information on performance of visual choice-reaction tasks. We review empirical findings and theoretical explanations from two domains, those of the Simon effect and the spatial Stroop effect, in which stimulus location has been shown to affect reaction time when irrelevant to the task. Wethen integrate the findings and explanations from the two domains to clarify how and why stimulus location influences performance even when it is uninformative to the correct response. Factors that influence the processing of irrelevant location information include response modality, relative timing with respect to the relevant information, spatial coding, and allocation of attention. The most promising accounts are offered by models in which response selection is a function of (1) strength of association of the irrelevant stimulus information with the response and (2) temporal overlap of the resulting response activation with that produced by the relevant stimulus information.The role played by stimulus location in visual information processing has been a controversial issue. This issue has been investigated primarily by means ofvisual search tasks in which a target stimulus in an array of distractors must be detected or identified. Reaction time (RT) in such tasks is typically an increasing function ofarray size, and accuracy a decreasing function, when the target is defined by a conjunction of features (e.g., Treisman & Gelade, 1980;Van Zandt & Townsend, 1993), leading some authors to propose that attending to location is necessary for feature integration (e.g., Nissen, 1985;Treisman & Gelade, 1980). As expected if location must be attended in such situations, a stimulus for a second task shows a processing benefit when it occurs in a location adjacent to the target stimulus of the search task rather than in a more remote location (e.g., Hoffman & Nelson, 1981), and precuing the location in the array in which the target stimulus will occur facilitates its processing (e.g., Eriksen & Hoffman, 1972). However, facilitation from a location precue is also apparent when the target is presented alone and requires only a detection response (e.g., Bashinski & Bacharach, 1980;Posner, Snyder, & Davidson, 1980), suggesting that it may be necessary to attend to the locaWe would like to thank Bernhard Hommel, Colin MacLeod, Bob Melara, Jim Neely, Richard Schweickert, Richard Simon, and Howard Zelaznik for helpful comments on previous versions of this manuscript. Reprint requests should be sent to Chen-Hui Lu, Department of Psychology, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, or Robert W. Proctor, Department of Psychological Sciences, Purdue University, West Lafayette, IN 47907-1364. tion of any stimulus on which a response is based. Consistent with this possibility, Tsal and Lavie (1993) recently showed that when the relevant feature of a precue stimulus is nonspatial (e.g., color), there is still facilitation in the identification of a s...

Recent studies have shown that the effects of irrelevant spatial stimulus-response (S-R) correspondence (i.e., the Simon effect) occur only after trials in which the stimulus and response locations corresponded. This has been attributed to the gating of irrelevant information or the suppression of an automatic S-R route after experiencing a noncorresponding trial-a challenge to the widespread assumption of direct, intentionally unmediated links between spatial stimulus and response codes. However, trial sequences in a Simon task are likely to produce effects of stimulus- and response-feature integration that may mimic the sequential dependencies of Simon effects. Four experiments confirmed that Simon effects are eliminated if the preceding trial involved a noncorresponding S-R pair. However, this was true even when the preceding response did not depend on the preceding stimulus or if the preceding trial required no response at all. These findings rule out gating/suppression accounts that attribute sequential dependencies to response selection difficulties. Moreover, they are consistent with a feature-integration approach and demonstrate that accounting for the sequential dependencies of Simon effects does not require the assumption of information gating or response suppression.

Differences in performance with various stimulus-response mappings are among the most prevalent findings for binary choice reaction tasks. The authors show that perceptual or conceptual similarity is not necessary to obtain mapping effects; a type of structural similarity is sufficient. Specifically, stimulus and response alternatives are coded as positive and negative polarity along several dimensions, and polarity correspondence is sufficient to produce mapping effects. The authors make the case for this polarity correspondence principle using the literature on word-picture verification and then provide evidence that polarity correspondence is a determinant of mapping effects in orthogonal stimulus-response compatibility, numerical judgment, and implicit association tasks. The authors conclude by discussing implications of this principle for interpretation of results from binary choice tasks and future model development.

A framework for action planning, called ideomotor theory, suggests that actions are represented by their perceivable effects. Thus, any activation of the effect image, either endogenously or exogenously, will trigger the corresponding action. We review contemporary studies relating to ideomotor theory in which researchers have investigated various manipulations of action effects and how those effects acquire discriminative control over the actions. Evidence indicates that the knowledge about the relation between response and effect is still a critical component even when other factors, such as stimulus-response or response-response relations, are controlled. When consistent tone effects are provided after responses are made, performance in serial-reaction tasks is better than when the effects are random. Methodology in which acquisition and test stages are used with choice-reaction tasks shows that an action is automatically associated with its effect bilaterally and that anticipation of the effect facilitates action. Ideomotor phenomena include stimulus-response compatibility, in which the perceptual feature of the stimulus activates its corresponding action code when the stimulus itself resembles the effect codes. For this reason, other stimulus-driven action facilitation such as ideomotor action and imitation are treated as ideomotor phenomena and are reviewed. Ideomotor theory also implies that ongoing action affects perception of concurrent events, a topic which we review briefly. Issues concerning ideomotor theory are identified and evaluated. We categorize the range of ideomotor explanations into several groups by whether intermediate steps are assumed to complete sensorimotor transformation or not and by whether a general theoretical framework or a more restricted one is provided by the account.

Studies of perceptual and cognitive matching often find (a) that same judgments are faster than different judgments (the same-different disparity) and (b) that same judgments to physically identical stimuli are faster than those to nominally identical, but physically dissimilar, stimuli (the name-physical disparity). The most widely accepted explanations of these phenomena propose quite different bases for them. The present article develops a single theoretical framework that accounts for both phenomena. Three processes are shown to contribute to the reaction time differences for single-letter pairs: the level of processing at which the match is performed, facilitation in the rate at which repeated stimuli are encoded, and inhibition that occurs when competing name codes are activated. The inhibitory process contributes to both simultaneous and sequential matches. Level of processing, however, contributes only to simultaneous matches, whereas the facilitory process contributes only to sequential matches. The theoretical framework that is developed accounts for the majority of data that have been obtained regarding the same-different and name-physical disparities. Several findings are reinterpreted in terms of the theory. More importantly, the theory serves an integrative role. The relationship between the same-different disparity and the name-physical disparity is clarified, and a wide range of additional phenomena obtained with the matching task are organized within the framework. The theory also relates the matching-task phenomena to more general processing principles apparent in other areas of research.Perceptual and cognitive matching tasks range of issues. These include not only issues have received extensive use in recent years regarding the underlying processes involved (see Nickerson, 1972;Posner, 1978). Such in matching two stimuli (e.g., Krueger, tasks involve either simultaneous or sequen-1978;Miller, 1978; Posner & Mitchell, tial presentation of pairs of stimuli that sub-1967) but also issues of a more general najects judge to be the same or different ac-ture, such as differences in the processing cording to criteria set by the experimenter, of familiar and unfamiliar stimuli (e.g., Am-The dependent variable most commonly bier & Proctor, 1976), attentional demands measured is the time to respond appropri-of processing (e.g., Posner & Boies, 1971; ately to each stimulus pair. Proctor & Fisicaro, 1977), mental manipu-Variations of the matching task have lation of visual patterns (e.g., Metzler & proved to be useful in examining a wide Shepard, 1974), and short-term retention of visual information (e.g., Posner, Boies, Ei-I would like to thank Cecilia Champion and Steve chelman, & Taylor, 1969). Welch for their assistance in conducting the experiments Despite the Wide variety of research conreported in this article. I am particularly grateful to ducted with the matching task, there has Janet Proctor for her careful critiques of the manuscript been little agreement regarding the exact "itaSSR reprints sh...

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Most studies that examined the precuing of motor responses have been interpreted as indicating that response specification is a variable-order process. An apparent exception to this conclusion was obtained by Miller (1982) for the preparation of discrete finger responses. Precuing was beneficial only when the precued responses were on the same hand, suggesting that response specification occurs in a fixed order, with hand specified before other aspects of the response. Three experiments examined this discrepant finding for discrete finger responses. Experiment 1 demonstrated that with sufficient time (3 s), all combinations of responses can be equally well prepared. Experiments 2 and 3 showed that the precuing advantage for same-hand responses at shorter precuing intervals is due to strategic and decision factors, not to an ability to prepare these responses more efficiently. Preparation of finger responses, thus, also appears to be variable. This conclusion poses problems for Miller's extension of the precuing procedure to the evaluation of discrete versus continuous models of information processing.

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