Spatial Processes in Category Assignment.

Investigates the hypothesis that spatial processes are involved in judgments on membership in a category. It is argued that membership versus nonmembership of an object or a concept, in a category, is spatially simulated in mental space by a minimal continuum with 2 levels, left for membership and right for nonmembership. In analogy to other embodied dimensions (e.g., time line or number line), the orientation of membership levels on the mental dimension is assumed to follow the acquired reading/writing schema, with procedural primacy implying dominance, hence leftward positioning of dominant elements. This rationale is tested in 7 experiments. A recognition memory paradigm (modified 2AFC paradigm, Experiment 1) revealed that participants were faster indicating the location of an old word on the screen when displayed left within a pair of words, indicating a spatial representation of category membership ("member" = left, "nonmember" = right). For category discrimination (Experiment 2) we found faster and more accurate performance when a target word is presented left as compared with right. This pattern is replicated in Experiments 4a and 4b, with different response alternatives. Discriminating categories in a stimulus-response compatibility paradigm (Experiment 3), participants were faster making correct responses with their left hand than with their right hand in target category trials. In contrast, no differences were found for distractor trials. Experiments 5a and 5b address the spatial bias in spontaneous sorting situations. Overall, this pattern of results across the 7 experiments provides evidence in support of a spatial simulation of category assignment.