The enhanced Simon effect for older adults is reduced when the irrelevant location information is conveyed by an accessory stimulus

The Simon effect, better performance when irrelevant stimulus location corresponds with the response location than when it does not, typically is larger for older than younger adults. However, Simon and Pouraghabagher [Simon, R. J., & Pouraghabagher, A. R. (1978). The effect of aging on the stages of processing in a choice reaction time task. Journal of Gerontology, 33, 553-561] found no age difference using an accessory-stimulus Simon task in which the relevant dimension was the color of a visual stimulus and the irrelevant dimension the location of a tone. Experiment 1 confirmed that older adults show a larger Simon effect than younger adults for the visual Simon task and that this age-related deficit is reduced or eliminated for the auditory-accessory task. Experiment 2 provided evidence suggesting that a small part of the age-related deficit in the visual Simon task is due to having to code the location of the relevant stimulus, but Experiment 3 showed that the majority of the deficit is due to the relevant and irrelevant information being conveyed by the same stimulus. Reaction-time distribution analyses show similar functions for younger and older adults, suggesting that the time course of activation is similar for both age groups.     

The influence of dimensional overlap on location-related priming in the Simon task

Choice reaction times are shorter when stimulus and response locations are compatible than when they are incompatible as in the Simon effect. Recent studies revealed that Simon effects are strongly attenuated when there is temporal overlap with a different high-priority task, accompanied by a decrease of early location-related response priming as reflected in the lateralized readiness potential (LRP). The latter result was obtained in a study excluding overlap of stimulus location with any other dimension in the tasks. Independent evidence suggests that location-related priming might be present in conditions with dimensional overlap. Here we tested this prediction in a dual-task experiment supplemented with recording LRPs. The secondary task was either a standard Simon task where irrelevant stimulus location overlapped with dimensions of the primary task or a Stroop-like Simon task including additional overlap of irrelevant and relevant stimulus attributes. At high temporal overlap, there was no Simon effect nor was there stimulus-related response priming in either condition. Therefore stimulus-triggered response priming seems to be abolished in conditions of limited capacity even if the likelihood of an S–R compatibility effect is maximized.     

Processing irrelevant location information: Practice and transfer effects in choice-reaction tasks

Left or right keypresses to a relevant stimulus dimension are faster when the stimulus location, although irrelevant, corresponds with that of the response than when it does not. This phenomenon, called the Simon effect, persisted across 1,800 trials of practice, although its magnitude was reduced. Practice with the relevant stimulus dimension presented at a centered location had little influence on the magnitude of the Simon effect when irrelevant location was varied subsequently, and practice with location irrelevant prior to performing with location relevant slowed responses. After practice responding to stimulus location with an incompatible spatial mapping, the Simon effect was reversed (i.e., responses were slower when stimulus location corresponded with response location) when location was made irrelevant. When the response keys were labeled according to the relevant stimulus dimension (the Hedge and Marsh [1975] task variation), this reversal from practice with a spatially incompatible mapping was found for both the congruent and the incongruent relevant stimulus-response mappings. Thus, task-defined associations between stimulus location and response location affect performance when location is changed from relevant to irrelevant, apparently through producing automatic activation of the previously associated response.     

Display-control arrangement correspondence and logical recoding in the Hedge and Marsh reversal of the Simon effect

When left and right keypresses are made to stimuli in left and right locations, and stimulus location is irrelevant to the task, responses are typically faster when stimulus location corresponds with response location than when it does not (the Simon effect). This effect reverses when the relevant stimulus-response mapping is incompatible, with responses being slower when stimulus and response locations correspond (the Hedge and Marsh reversal). Simon et al. (Acta Psychol. 47 (1981) 63) reported an exception to the Hedge and Marsh reversal for a situation in which the relevant stimulus dimension was the color of a centered visual stimulus and the irrelevant location information was left or right tone location. In contrast, similar experiments have found a reversal of the Simon effect for tone location when relevant visual locations were mapped incompatibly to responses. We conducted four experiments to investigate this discrepancy. Both results were replicated. With an incompatible mapping, irrelevant tone location showed a small reverse Simon effect when the relevant visual dimension was physical location but not when the color of a centered stimulus or the direction in which an arrow pointed conveyed the visual location information. The reversal occurred in a more standard Hedge and Marsh task in which the irrelevant dimension was location of the colored stimulus, but only when the response keys were visibly labeled. Several of the results suggest that display-control arrangement correspondence is the primary cause of the Hedge and Marsh reversal, with logical recoding playing only a secondary role.     

Influence of temporal overlap on time course of the Simon effect

Two experiments are reported in which we manipulated relevant and irrelevant stimulus dimensions to assess whether an increase in temporal overlap would influence the time course of a "standard" Simon effect (obtained when visual stimuli are presented on the left/right of the screen and left/right responses are performed with uncrossed hands). This procedure is new in two ways: First, the manipulations were intended to reduce, instead of increase, the distance between conditional and unconditional response-activation processes. Second, we manipulated the relevant and irrelevant stimulus dimensions in a manner that did not vary stimulus onset asynchronies, precues, or go/no go trials, or alter the stimulus quality. Results were consistent with the hypothesis that when the two response processes are shifted closer to each other, the Simon effect would be sustained across time, instead of decreasing as typically found. These findings are discussed in line with the temporal overlap hypothesis and with an automatic activation account.     

The influence of irrelevant location information on performance: A review of the Simon and spatial Stroop effects

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. We then 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.     

Stimulus–response correspondence effect as a function of temporal overlap between relevant and irrelevant information processing

The stimulus–response correspondence (SRC) effect refers to advantages in performance when stimulus and response correspond in dimensions or features, even if the common features are irrelevant to the task. Previous research indicated that the SRC effect depends on the temporal course of stimulus information processing. The current study investigated how the temporal overlap between relevant and irrelevant stimulus processing influences the SRC effect. In this experiment, the irrelevant stimulus (a previously associated tone) preceded the relevant stimulus (a coloured rectangle). The irrelevant and relevant stimuli onset asynchrony was varied to manipulate the temporal overlap between the irrelevant and relevant stimuli processing. Results indicated that the SRC effect size varied as a quadratic function of the temporal overlap between the relevant stimulus and irrelevant stimulus. This finding extends previous experimental observations that the SRC effect size varies in an increasing or decreasing function with reaction time. The current study demonstrated a quadratic function between effect size and the temporal overlap.     

Influences on the Simon effect of prior practice with spatially incompatible mappings: Transfer within and between horizontal and vertical dimensions

The Simon effect refers to the fact that for tasks in which stimulus location is irrelevant and a nonspatial attribute is relevant, responses are typically faster when stimulus and response locations correspond than when they do not. Two experiments examined the influence of prior practice with an incompatible relevant spatial mapping on the Simon effect as a function of the dimension (vertical or horizontal) along which the stimuli and responses varied in practice and transfer sessions. With 72 practice trials, the Simon effect in the transfer session was eliminated only when the spatial dimension was horizontal for both practice and transfer. With 600 practice trials, the Simon effect was eliminated for all combinations of practice and transfer dimensions, with noncorresponding responses showing an advantage when the dimension was horizontal for both practice and transfer. Within-dimension transfer effects for the horizontal dimension after a small amount of practice can be attributed to reactivation of specific stimulus-response associations defined for the practice task. However, the between-dimension transfer effects evident after a larger amount of practice cannot be explained in this manner and suggest that the subjects acquired a general procedure of responding opposite to the stimulus location.     

The relationship between stimulus processing and response selection in the Simon task: Evidence for a temporal overlap

Summary As is indicated by the Simon effect, choice reactions can be carried out faster when the response corresponds spatially to the stimulus, even if the stimulus location is irrelevant to the task. In Experiments 1–4 the relationships between the Simon effect and stimulus eccentricity, signal quality, and signal-background contrast are investigated. The Simon effect was found to interact with all of these factors, at least when manipulated blockwise. These results are at odds with previous results and are difficult to interpret from an additive-factor-method view. An alternative interpretation is suggested that attributes the results to the temporal relationship between the processing of the relevant stimulus information and stimulus location. The assumption is that a decrease in the Simon effect is caused by every experimental manipulation that markedly increases the temporal distance between the coding of the relevant stimulus information and that of the irrelevant stimulus location. This assumption was tested in Experiment 5 in a more direct way. The stimuli were built up on a screen over time, so that the temporal distance between the presence of location and identity information could be controlled experimentally. The results provide further support for a temporal-delay interpretation of interactions between irrelevant stimulus-response correspondence and factors that affect early stages of information processing.     

Differential dynamics of spatial and non-spatial stimulus-response compatibility effects: a dual task LRP study

Choice reaction times are shorter when stimulus and response features are compatible rather than incompatible. Recent studies revealed that spatial compatibility effects in Simon tasks are strongly attenuated when there is temporal overlap with a different high-priority task. In contrast, non-spatial variants of the Simon task appear to be unaffected by task overlap. The present study used the lateralized readiness potential (LRP) within a dual task design to elucidate the dynamics underlying these differential effects for a color and a spatial variant of the Simon task. In the color version there was no sign of early response priming by irrelevant stimulus features in the LRP. The color compatibility effect was independent of task overlap and reflected in the LRP onset latency. In contrast, in the spatial version, priming by irrelevant stimulus location showed up and was mirrored by early LRP activation. Response priming and the corresponding Simon effect, however, were present only in case of little temporal overlap with the primary task. The absence of spatial compatibility effects at strong temporal overlap suggests that response conflicts due to stimulus-related priming depend on the availability of processing resources.     

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.     

Perceptual and attentional factors in encoding irrelevant spatial information

Numerous studies found superior performance when the irrelevant location of a stimulus and response location were corresponding than when they were not corresponding (Simon effect), suggesting that stimulus location is processed in an obligatory manner. The present study compared Simon effects from the location of a relevant (i.e., to-be-attended) object to those from the location of an irrelevant (i.e., to-be-ignored) object. In four experiments, participants were presented with a rectangular frame and a square, with the relevant object in green or red color and the irrelevant object in gray or white color. Participants’ task was to respond with a lateral keypress to the color of the relevant object, and we varied spatial correspondence between the location of the relevant or the irrelevant object and the response, respectively. Results consistently showed larger Simon effects from the location of the relevant than from the irrelevant object, even when the irrelevant object was made very salient. These results suggest that location processing is largely confined to relevant (i.e., attended) objects, stressing the role of attention shifts for location encoding.     

On the generality of the affective Simon effect

In affective Simon studies, participants are to select between a positive and negative response on the basis of a nonaffective stimulus feature (i.e., relevant stimulus feature) while ignoring the valence of the presented stimuli (i.e., irrelevant stimulus feature). De Houwer and Eelen (1998) showed that the time to select the correct response is influenced by the match between the valence of the response and the (irrelevant) valence of the stimulus. In the affective Simon studies that have been reported until now, only words were used as stimuli and the relevant stimulus feature was always the grammatical category of the words. We report four experiments in which we examined the generality of the affective Simon effect. Significant affective Simon effects were found when the semantic category, grammatical category, and letter-case of words was relevant, when the semantic category of photographed objects was relevant, and when participants were asked to give nonverbal approach or avoidance responses on the basis of the grammatical category of words. Results also showed that the magnitude of the affective Simon effect depended on the nature of the relevant feature.     

Towards a common processing architecture underlying Simon and SNARC effects

It has been shown repeatedly that relatively small numbers are responded to faster with the left hand and relatively large numbers are responded to faster with the right hand. This so-called SNARC effect (Dehaene, Bossini, & Giraux, 1993) is thought to arise through activation of irrelevant spatial codes associated with the magnitude of the number. This conflict between irrelevant magnitude information and the response is conceptually similar to the well-known Simon effect. Recently, both Mapelli, Rusconi, and Umiltà (2003) and Keus and Schwarz (in press) directly compared both effects in a single task within the framework of the additive factor method (Sternberg, 1969). While Mapelli et al. found additive effects of SNARC and Simon levels, suggesting different processing stages, Keus and Schwarz found that the SNARC effect depended on the compatibility level of the Simon task leading them to propose a common origin at the response selection stage. In the present study we demonstrate in 2 experiments that the relationship between Simon and SNARC depends on the relevance of the magnitude code, thereby violating one of the core assumptions of the AFM. Instead we propose a temporal overlap model to interpret the relationship between these effects which allows to commensurate apparently divergent outcomes.     

Co-occurrence of sequential and practice effects in the Simon task: Evidence for two independent mechanisms affecting response selection

The Simon effect refers to the observation that responses to a relevant stimulus dimension are faster and more accurate when the stimulus and response spatially correspond than when they do not, even though stimulus position is irrelevant. Recent findings have suggested that the Simon effect can be strongly modulated by prior practice with a spatially incompatible mapping and by correspondence sequence. Although practice is thought to influence conditional stimulus —response (S-R) processing, leaving response priming through the unconditional route unaffected, sequential effects are thought to represent trial-by-trial adaptations that selectively involve unconditional S —R processing. In the present study, we tested this assumption by assessing the effects of correspondence sequence both when the Simon task alone was performed and when it was preceded by a spatial compatibility task with either incompatible (Experiments 1-2) or compatible (Experiment 2) instructions. The observation that practice and correspondence sequence co-occur and exert additive effects strongly demonstrates that the two factors affect different processing routes.     

Coding controlled and triggered cursor movements as action effects: influences on the auditory Simon effect for wheel-rotation responses

Four experiments investigated influences of irrelevant action effects on response selection in Simon tasks for which tone pitch was relevant and location irrelevant, and responses were clockwise- counterclockwise wheel rotations. When the wheel controlled left-right movement of a cursor in a direction opposite an instructed left-right hand-movement goal, the Simon effect was reduced. When the wheel was held at the bottom, this reduction was due to some participants coding responses relative to the cursor and others relative to the hands. However, when the wheel was held at the top, it was due to participants integrating cursor movements with hand movements as a single action concept. In contrast, a cursor triggered by the wheel movement showed little influence on the Simon effect, even when contiguity and contingency with the wheel movements were high. Experience with the controlled cursor in a prior trial block or between trials established a causal relation that enabled participants to code the triggered cursor as belonging to the action concept and thus reduce the Simon effect. Multiple factors determine the influence of an irrelevant action effect on performance.     

Attention precuing and Simon effects: A test of the attention-coding account of the Simon effect

Simon effects refer to the finding that choice-response latencies to a nonspatial aspect of a stimulus vary depending on the spatial correspondence between the stimulus position and the position of the correct response alternative. Recently, researchers have proposed an attention-coding account of Simon effects whereby the (irrelevant) stimulus spatial code involved in the generation of the effect is formed in the process of attentional orienting to the stimulus. This account predicts that if attentional orienting is unnecessary at stimulus onset, as when the stimulus appears at an attended location, Simon effects will not be observed. This prediction was tested by measurement of Simon effects in an attention-precuing task in which the stimulus was presented at attended and unattended locations. Significant Simon effects were observed independently of the focus of attention. This result was obtained over a large range of precue-target SOAs, and did not depend on whether central or peripheral precues were used to direct attention or on whether the relevant target dimension was color or form. Significant Simon effects were not observed when the precue-target SOA was 50 ms, irrespective of the other precue and task conditions. The data do not support the prediction of the attention-coding account and thus question the generality of the account in its current form. It is suggested that spatial and temporal uncertainties are important factors that influence the pattern of results, and that these factors must be incorporated into attention-coding models of the Simon effect.     

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.     

Spontaneous decay of response-code activation

Summary Two experiments investigated whether theTwo experiments investigated whether the Simon effect (i. e.., faster responses to spatially corresponding than to noncorresponding stimuli, with stimulus location being irrelevant) is affected by the frequency of noncorrespondence trials. Stimulus discriminability (Experiment 1) and immediate or delayed stimulus formation (Experiment 2) was varied in order to manipulate the temporal relationship between coding of the relevant stimulus information and of stimulus location. As was expected, the Simon effect decreased from high to low discriminability and from immediate- to delayed-stimulus formation. This is consistent with the notion of a gradual decay of location-induced response-code activation. Moreover, the Simon effect decreased with increasing frequency of noncorrespondence trials and was even reversed with higher frequency. This demonstrates strategic preparation of stimulus processing and/or response selection based on irrelevant location information. However, frequency did not modify the interaction between S-R correspondence and stimulus discriminability or stimulus formation, this suggesting that code decay is not a result of a strategy, but an automatic process.     

Developmental trends in the interaction between auditory and linguistic processing

The developmental course of multidimensional speech processing was examined in 80 children between 3 and 6 years of age and in 60 adults between 20 and 86 years of age. Processing interactions were assessed with a speeded classification task (Garner, 1974a), which required the subjects to attend selectively to the voice dimension while ignoring the linguistic dimension, and vice versa. The children and adults exhibited both similarities and differences in the patterns of processing dependencies. For all ages, performance for each dimension was slower in the presence of variation in the irrelevant dimension; irrelevant variation in the voice dimension disrupted performance more than irrelevant variation in the linguistic dimension. Trends in the degree of interference, on the other hand, showed significant differences between dimensions as a function of age. Whereas the degree of interference for the voice-dimension-relevant did not show significant age-related change, the degree of interference for the word-dimension-relevant declined significantly with age in a linear as well as a quadratic manner. A major age-related change in the relation between dimensions was that word processing, relative to voice-gender processing, required significantly more time in the children than in the adults. Overall, the developmental course characterizing multidimensional speech processing evidenced more-pronounced change when the linguistic dimension, rather than the voice dimension, was relevant.