Academic journal article Canadian Journal of Experimental Psychology

Parametric Exploration of the Simon Effect across Visual Space

Academic journal article Canadian Journal of Experimental Psychology

Parametric Exploration of the Simon Effect across Visual Space

Article excerpt

Abstract

The Simon effect refers to the performance advantage for responding to the nonspatial identity of the target when the target's irrelevant location corresponds with the relative location of the response. The present study is a parametric examination of the magnitude of the Simon effect across visual space. Response keys were arranged along vertical, horizontal, and two diagonal axes, and stimuli were arranged in two concentric circles (near and far from fixation) along the same axes. The results show that the Simon effect is of similar magnitude regardless of stimulus-response axis. In contrast to findings from stimulus-response compatibility paradigms, there was no evidence in this study for the presence of an orthogonal compatibility effect or left-right prevalence effect, suggesting that these effects only arise when response location is relevant. The results demonstrate the robust generalizability of the Simon effect under different spatial conditions and thus broaden the relevance of the Simon effect to a variety of applications.

When the location of a stimulus is used to select a spatially coded response (e.g., a left or right key-press to a stimulus on the left or right), reaction times are generally faster and more accurate if the stimulus-response mappings are compatible (i.e., a right response to a right stimulus) than if they are incompatible (i.e., a right response to a left stimulus). The performance difference in the compatible versus the incompatible condition is referred to as the spatial compatibility effect. Stimulus-response mappings also can influence performance when spatially defined responses are selected according to a nonspatial feature of the stimulus (e.g., shape, colour, etc.) and stimulus location is irrelevant. In this case, corresponding responses (i.e., a right response to a stimulus presented on the right) are generally faster and more accurate than noncorresponding responses (i.e., a right response to a left stimulus) even when the location of the stimulus is irrelevant to the response. This performance difference between corresponding and noncorresponding responses is referred to as the Simon effect (Lu & Proctor, 1995; Simon, 1990).

A common thread among explanations of the Simon effect is that the spatial location code of the stimulus can facilitate or interfere with the selection of the correct spatial response (Kornblum, Hasbrouq, & Osman, 1990). Previous work (e.g., Ivanoff & Peters, 2000; Nicoletti & Umiltà, 1989, 1994; Notebaert, Soetens, & Melis, 2001; Rubichi, Nicoletti, Iani, & Umiltà, 1997; Stoffer & Umiltà, 1997) suggests that the spatial location code of the stimulus is formed with respect to the direction of attention since the position of the stimulus seems to be less important that the last shift of attention. There is also evidence, however, that multiple spatial location codes are activated in a Simon task (Lamberts, Tavernier, & d'Ydewalle, 1992). Context also appears important (Hommel & Lippa, 1995) as the reference frame within which the Simon effect is coded is flexible.

The nature of the co-ordinate system responsible for the Simon effect has not yet been fully determined. Using left and right response locations, Wallace (1971, 1972) found that reaction times (RTs) to up and down stimulus locations were between RTs for corresponding and noncorresponding targets, from which he concluded that the Simon effect was the result of facilitation and interference from spatial codes. This conclusion is reasonable given that the preactivation of a response speeds RTs and that the preactivation of another response will result in conflict (i.e., the activation of two or more responses) that can be resolved, but not without a cost to RTs. When the stimulus is presented at a location that is perfectly orthogonal to the "response axis" (e.g., a stimulus that is presented up or down on an imaginary vertical axis with responses made by horizontal left and right key-presses), there is no obvious overlap between stimulus and response spatial codes, and therefore responding will neither suffer nor benefit from the spatial feature of the stimulus. …

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