Dimensional interactions in vibrotactile information processing

The effect of irrelevant dimensional variation on the processing of vibrotactile stimuli was measured. Six observers performed a speeded classification task with stimuli varying along the dimensions of pitch and loudness. Choice reaction times were obtained for stimuli differing on one dimension alone, on two correlated dimensions, or on two orthogonally varied dimensions. Compared to one-dimension performance, reaction times were faster in the correlated condition and slower in the orthogonal condition. In general, these findings agreed with similar experiments in other modalities, with the exception that the effects in this study tended to be stronger for cases in which loudness, rather than pitch, was the relevant dimension. The results are explained in terms of the integrality of pitch and loudness and of the relative discriminability of dimensions.