The effect of time pressure and the spatial integration of the stimulus dimensions on overall similarity categorization

A free classification study is presented in which the effect of time pressure and the spatial integration of the stimulus dimensions on overall similarity sorting is investigated. A 2 x 2 between-subjects factorial design was employed with the factors being the level of time pressure (high/low) and the spatial integration of the stimulus dimensions (high/low). The results showed, consistent with Milton and Wills (2004), that spatially separable stimuli resulted in a greater level of overall similarity sorting than more spatially integrated dimensions. Furthermore, participants under low time pressure produced a greater level of overall similarity sorting than those under high time pressure, consistent with Milton, Longmore and Wills (2008). Critically, there was also a significant interaction between time pressure and the level of spatial integration, with the integration effect being greater under low time pressure than under high time pressure. These findings provide support for the idea that overall similarity sorting can be the result of an effortful, deliberative process.