Discrimination of Length by Sight and Touch

Abstract

This article reports a further investigation into the capacity to compare objects seen with objects touched. An earlier experiment had suggested that cross-modal comparisons are quite as accurate as comparisons made within the same modality: comparing a visual with a tactual stimulus showed no loss in sensitivity vis-à-vis comparisons of visual with visual and tactual with tactual stimuli (Kelvin, 1954). The results of the experiment reported below make it clear that the earlier findings, and their interpretation, were due to an oversimplified experimental situation. It now seems that cross-modal comparisons are a function of the total range of the comparison stimuli and not simply a function of the physical properties of isolated stimuli, as the first report suggested. Indeed, the present investigation makes it doubtful whether cross-modal matching is ever more than an experimental artefact.