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Two competing models of the effects of pattern element proximity, masking, and perceptual integration on the discriminability of spatiotemporal vibrotactile patterns are compared. Kirman's 'integration hypothesis' predicts that pattern perception is facilitated by a process of perceptual integration which requires that pattern elements be presented in close spatial and temporal proximity. Conversely, the 'isolation hypothesis' predicts that the strong masking effects which occur when pattern elements are presented in close proximity impede the perception of patterns. Traditional masking studies do not provide a fair test of these two hypothesis because they rely on methods that measure the subject's ability to identify the target when the target is presented in conjunction with the mask, rather than the discriminability of the complex percept resulting from the integration of the target and mask. To account for this, a new procedure was devised where the amount of interelement masking and the discriminability of the pattern as a whole were measured independently as the spatial and temporal separation of the pattern elements were varied. As expected under both hypotheses, masking between pattern elements increased as either the spatial or the temporal separation between them was decreased. The pattern discrimination data also support the isolation hypothesis in that the patterns were discriminated less well with increasing temporal element separation with a similar but nonsignificant trend in the case of spatial separation. It is concluded that this new methodology should be applied to a wider range of tactile pattern processing situations in order to assess the generality of the results obtained.

The extent to which auditory, tactile, and visual perceptual representations are similar, particularly when dealing with speech and speech-like stimuli, was investigated. It was found that comparisons between auditory and tactile patterns were easier to perform than were similar comparisons between auditory and visual stimuli. This was true across a variety of styles of tactile and visual display, and was not due to limitations in the discriminability of the visual displays. The findings suggest that auditory and tactile representations of stimuli are more alike than are auditory and visual ones. It was also found that touch and vision differ in terms of the style of information distribution which they process most efficiently. Touch dealt with patterns best when the pattern was characterised by changes across time, whereas vision did best when spatially or spatiotemporally distributed patterns were presented. As the sense of hearing also seems to specialise in the processing of temporally ordered patterns, these results suggest one way in which the senses of hearing and touch differ from vision.

The relationship between Inspection Time (a perceptual discrimination task designed to estimate the rate at which a subject processes sensory input) and the Wechsler Adult Intelligence Scale (WAIS) was assessed in a sample of 29 university students. Sixteen ofthe subjects ("strategy users") independently developed a strategy for performing the task, based on apparent movement cues. The remaining 13 ("non-users") did not develop the strategy and could not easily be trained in its use. Strategy users had slightly faster Inspection Times than non-users, but were not significantly different from the non-users on the WAIS or any of the subtests. However, the two groups differed substantially in the relationship of Inspection Time to IQ. In the strategy users, Inspection Time was not significantly related to IQ or to any of the WAIS subtests. In the non-users, Inspection Time was highly correlated with Performance IQ and with scores on two of the subtests. Methodological implications of the differences between strategy users and non-users, and the theoretical status of Inspection Time as a measure of mental speed, are discussed.The authors gratefully acknowledge the advice and assistance of Ted Nettelbeck and Chris Brand in designing and setting up the study, and the enormous contribution of James Alexander in writing the Inspection Time program.Requests for reprints should be sent to Brian Mackenzie,

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