Tactual perception: a review of experimental variables and procedures <s> Vibrations <s> Katz (1925) has argued that the sense of vibration underlies the tactual perception of roughness. However, Taylor and Lederman (1975) have suggested that vibration serves only to prevent the cessation of mechanoreceptor activity. In an experimental evaluation of these positions, it is shown that, although prior (selective) adaptation of the fingertip strongly affects the perceived magnitude of supraliminal vibrotactile signals, it fails to alter the perceived roughness of metal gratings. The results thus favor the Taylor and Lederman position. The paper also speculates on roughness coding by the mechanoreceptor populations present in glabrous skin of the human hand. <s> BIB001 </s> Tactual perception: a review of experimental variables and procedures <s> Vibrations <s> Subjects are more accurate in identifying a vibrotactile pattern when it is presented in isolation than when it is presented in temporal and spatial contiguity with a second vibrotactile pattern. When the temporal separation between the two patterns is relatively long (greater than 200 to 300 msec), there is more interference when the target pattern is presented second than when it is presented first, It was hypothesized that if features of a vibrotactile pattern persist for relatively long durations, the perception of a subsequent pattern might be interfered with. Two experiments investigated the persistence of tactual features. In both experiments, subjects were presented with two patterns and the temporal separation between the patterns was varied. The subjects were required to identify the second pattern. The results of Experiment 1 showed that at relatively long stimulus onset asynchronies, the subjects often erred and responded with a pattern containing more lines than were contained in the target pattern. Also, the subjects often overestimated the number of lines contained in the target patterns. These findings support the idea that features of vibrotactile patterns persist for relatively long durations and that these features may be integrated with subsequently presented patterns. The results of Experiment 2 indicated that the persisting representation was a veridical copy of the presented pattern and lasted as long as 1,200 msec. The results are discussed in terms of a tactile sensory register. <s> BIB002 </s> Tactual perception: a review of experimental variables and procedures <s> Vibrations <s> Abstract Objective : To determine the effect of different sites and locally applied pressure on vibration thresholds. Methods : Vibration thresholds were compared in 47 normal volunteers at 3 sites of the index finger (pulp, dorsum of the middle phalanx and nail) and at two sites of the great toe (dorsum of the proximal phalanx and nail). The effect of local pressure (30, 50 and 100 g/1.22 cm 2 ) were compared in 41 subjects at the dorsum of the middle phalanx of the index finger and the proximal phalanx of the great toe. Results : The hand was more sensitive than the foot for vibration. There were no significant differences in vibration thresholds at different sites of the index finger and different sites of the great toe. The pulp of the index finger yielded the least inter-individual variation. Testing under 30 and 50 g/1.22 cm 2 of pressure yielded equal vibration thresholds. Vibration threshold was higher when tested under 100 g/1.22 cm 2 at the index finger but not the great toe. This difference was small and clinically negligible. Conclusion : Testing of vibration thresholds in normal subjects can be adequately conducted at several sites of the index finger and the great toe. The test can be adequately done under low pressure of 30–50 g/1.22 cm 2 . <s> BIB003 </s> Tactual perception: a review of experimental variables and procedures <s> Vibrations <s> Previous research has shown that the presentation of spatially predictive auditory and vibrotactile warning signals can facilitate driver responses to driving events seen through the windscreen or rearview mirror. The present study investigated whether this facilitation reflects the priming of the appropriate response (i.e. braking vs. accelerating) or an attentional cuing effect (i.e. a perceptual benefit that facilitates subsequent behavioural responding). In the experiments reported here, participants had to discriminate the colour of a number plate (red vs. blue) following the presentation of either spatially predictive vibrotactile (experiment 1) or auditory (experiment 2) warning signals that indicated the likely location (front or back) of the visual target, while simultaneously performing a highly attention-demanding rapid serial visual presentation task. Numberplate discrimination performance was facilitated following the presentation of valid auditory cues, but not following the presentation of equally informative vibrotactile cues. The use of an orthogonal spatial cuing design enabled with us to rule out of a potential response priming account of these data. The results suggest that whilst directional congruency between a warning signal and a target event may be sufficient to facilitate performance due to the priming of the appropriate response, attentional facilitation effects may also require the co-location of the cue and target within the same functional region of space. <s> BIB004 </s> Tactual perception: a review of experimental variables and procedures <s> Vibrations <s> This article reviews various different approaches to the design of unimodal and multisensory warning signals, in particular warning signals for use in alerting drivers to potentially dangerous situations. The design of optimal warning signals that are maximally effective in terms of the limitations that constrain human information processing are discussed in light of the latest findings emerging from cognitive neuroscience research. A new approach to the design of multisensory warning signals, involving the presentation of warning signals in different regions of space around a driver, is then critically examined. <s> BIB005 </s> Tactual perception: a review of experimental variables and procedures <s> Vibrations <s> We use a vibrotactile-delayed match-to-sample paradigm to evaluate the effects of interference on working memory. One of the suggested mechanisms through which interference affects performance in working memory is feature overwriting: Short-term representations are maintained in a finite set of feature units (such as prefrontal neurons), and distractor stimuli co-opt some or all of those units, degrading the stored representation of an earlier stimulus. Subjects were presented with two vibrotactile stimuli and were instructed to determine whether they were of the same or different frequencies. A distractor stimulus was presented between the target and probe stimuli, the frequency of which was a function of the target stimulus. Performance on the task was affected by the frequency of the distractor, with subjects making more erroneous same judgments on different trials when the distractor frequency was closer to the probe than to the target, than when the distractor was further from the probe than the target. The results suggest that the frequency of the distractor partially overwrites the stored frequency information of the probe stimulus, providing support for the feature-overwriting explanation of working memory interference. <s> BIB006
The use of vibrating stimuli in tactile research has been common in the definition of tactile thresholds (e.g., BIB003 , tactile masking paradigms (e.g., BIB002 or tactile pattern perception (e.g.,  . Vibrations have also been studied under more applied areas, for instance the use of vibration as warning signals in driving (e.g., BIB004 BIB005 . Also, the perception of vibration has allowed the development of communication systems for sensorydeprived subjects, such as the Tadoma system, a system by which deaf-blind subjects are able to perceive speech by placing their hands on the speakers face and feeling the vibrations (e.g., Sherrick 1975) . Vibration is useful in the perception of roughness, and   mentioned the involvement of the sense of vibration in tactile perception. BIB001 confirmed the relevance of vibration in roughness perception and argued that vibration allowed continuous activation of the mechanoreceptors of the skin, facilitating texture perception. Vibrotactile stimulation has also been used within working memory paradigms. For instance BIB006 , using a matching to sample paradigm, explored interference effects in working memory. Participants had to determine whether two separate vibrotactile stimuli had the same frequency or not. Between the two stimuli, an interfering distractor was introduced. Results showed that the frequency of the distractor affected performance, with trials in which the distractor was more similar to the probe having more errors than trials in which the distractor was more similar to the target. The authors assume that the distractor was overwriting the probe stimuli and argue in favour of an overwriting system to explain interference effects in working memory. The use of vibrotactile stimuli, although more common in physiological (e.g.,  or psychophysical (e.g., Verrillo and Gescheider 1975) procedures, is also reported in perception and memory research, allowing the study of touch within controlled exposition conditions. Vibrations have the advantage of being a highly controlled stimuli in touch since the experimenters can strictly define where the vibration is applied, when the vibration is applied, its frequency, the size of the stimulated area and the duration of the stimulation.