Does perceptual simulation explain spatial effects in word categorization?

In three experiments we investigated the origin of the effects of the compatibility betweenthe typical location of entities denoted by written words (e.g., “up” foreagleand“down” forcarpet) and either the actual position of the words on the screen (e.g.,upper vs. lower part of the screen), or the response position (e.g., upper- vs. lower-key presses) in binary categorization tasks. Contrary to predictions of the perceptualsimulation account (Barsalou, 1999), conceptual spatial compatibility effects observedin the present study (faster RTs when the typical position of the stimulus referent inthe real word was compatible with either the stimulus or response physical position)seem to be independent of whether there was an overlap between simulated processespossibly triggered by the presented stimulus and sensory-motor processes actuallyrequired by the task. Rather, they appear to depend critically on whether the involvedstimulus and/or response dimensions had binary, variable (vs. fixed) values. Notably, nostimulus–stimulus compatibility effect was observed in Experiment 3, when the stimulusphysical position was presented in a blocked design (i.e., it was kept constant withineach block of trials). In contrast, in all three experiments, a compatibility effect betweenresponse position and another (non-spatial) conceptual dimension of the stimulus (i.e.,its semantic category) was observed (i.e., an effect analogous to the MARC [linguisticmarkedness of response codes] effect, which is usually observed in the number domain;Nuerk et al., 2004). This pattern of results is fully accounted for by the polarity principle,according to which these effects originate from the alignment of the polarities of eitherdifferent stimulus dimensions or stimulus and response dimensions.