Vibrotactile pattern recognition and discrimination at several body sites

Target patterns presented to uncued locations on a single fingerpad were followed by either sameshape (SS) maskers or different-shape (DS) maskers presented to either the same location (SLoc) or a different location (DLoc). DS maskers interfered with identification more when they were at SLoc than when they were at DLoc,but the reverse was true for SS maskers; they interfered more at DLoc than at SLoc. Whentargets were presented to cued locations, performance in the absence of maskers improved, but the pattern of interference from maskers resembled that for uncued presentation. The proportion of masker responses on incorrect trials revealed that both temporal masking and response competition may be involved in the effects of location on pattern identification.The present study examined whether the location of a pattern on the skin affects the ability to process information about its spatial features. Specifically, does location affect the ability to identify spatial patterns on a single fingerpad? The fingerpad was examined because of its high spatial resolution (Sathian & Zangaledze, 1996;Sherrick & Cholewiak, 1986;Stevens & Patterson, 1995;Van Boven & Johnson, 1994;Weinstein, 1968), because of its role in tactual exploration, and because it is used to process successive spatial patterns in tactile communication systems such as braille and the Optacon (Bliss, Katcher, Rogers, & Shepard, 1970). In studies using the Optacon vibratory array or similar dense arrays of vibrators, spatial patterns have usually been presented either to a single location or to locations on separate body sites. Some of the studies examining separate body sites have compared the pattern processing capabilities of the sites (Cholewiak & Craig, 1984;Craig, 1977;Loomis, 1980;Scadden, 1973). In other studies examining separate sites, patterns were presented to separate fingers and attentional factors were investigated (Craig, 1985a;Craig & Evans, 1995;Evans & Craig, 1991, 1992Evans, Craig, & Rinker, 1992;Horner, 1992Horner, , 1995Rinker & Craig, 1994). Relatively few studies have examined how spatial patterns are processed at adjacent locations on a single fingerpad.Hill (1974) indirectly measured the effects of presenting patterns to adjacent locations on the fingerpad when An earlier version of some of the material in Experiment I was presented at the annual meeting of the Psychonomic Society in November 1993. An earlier version of some of the material in Experiment 2 was presented at the annual meeting of the American Psychological Society in June 1995. This research was supported by the University of Wisconsin, Oshkosh, and by Grant DC-00095 from the Nationallnstitutes of Health. nT.H. wishes to thank James Craig for his comments on earlier versions of this manuscript and Roger Rhodes for his assistance in conducting these experiments. Correspondence should be addressed to D. T. Horner, Psychology Department, University of Wisconsin, Oshkosh, WI 54901-8601 (e-mail: homer@vaxa.cis.uwosh.edu).he examined Optacon reading rates using differ...

Section: Resultsmentioning

confidence: 99%

Section: University Of Wisconsin Oshkosh Wisconsinmentioning

confidence: 99%

Section: )mentioning

confidence: 99%

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The effect of shape and location on temporal masking of spatial vibrotactile patterns

Horner

1997

“…Responding "different" when the members of the pair were the same was considered a "false alarm." With the hit and false-alarm rates thus obtained, d' was computed for each SOA from a computer program (Cholewiak & Craig, 1984), and from each d' a P(C) max was computed, the proportion correct the subject would have achieved had the subject shown no response bias (McFadden, 1970). P(C) max is plotted as a function of SOA in Figure 3.…”

Section: Methodsmentioning

confidence: 99%

Attending to two fingers: Two hands are better than one

Craig

1985

Self Cite

The ability of subjects to attend to vibrotactile patterns presented to two fingers was explored in several experiments. The patterns were generated by two 6 column x 24 row tactile arrays. In one set of measurements, the arrays were placed in contact with the subjects' left index and middle fingers. Both discrimination and identification tasks suggested that there was an attentional deficit in processing patterns presented simultaneously to these two fingers. A pattern presented to either the middle or index finger was identified both more accurately and more rapidly than was the same pattern divided in half and presented to two fingers. Patterns were also presented to two fingers on opposite hands, and performance measures were taken on patternidentification tasks, on discrimination tasks, and on tasks that required subjects to combine pattern information from two fingers. All three measures showed performance to improve when the patterns were presented to two fingers on opposite hands relative to when they were presented to two fingers on the same hand. The results are interpreted to suggest, first, that subjects can process patterns simultaneously presented to two fingers on the same hand, but with some deficit due to attentional mechanisms, and second, that information from patterns presented to two fingers is processed differently depending on whether the two fingers are on the same or on different hands. There is much less of an attentional deficit in processing patterns presented simultaneously to two fingers on opposite hands.There has been relatively little work on the role of attention in the perception of tactile stimuli. In considering a task such as detection of a signal, the question of whether or not a subject can attend to more than one site has received mixed answers. Franzen, Markowitz, and Swets (1970) concluded that subjects could not attend to more than one finger at a time, whereas Craig (1968) concluded that subjects could combine weak signals from two fingers, implying that the two fingers could be attended to simultaneously. Subsequently, Shiffrin, Craig, and Cohen (1973) presented data to support an unlimited attention model for detection of simple stimuli by the skin. These studies did not, however, deal with the question of whether and how subjects could attend to patterned stimuli presented to more than one site at a time. Here the question is more than simply whether or not a stimulus was presented at a particular site; it is whether or not information from more than one site can be combined.It has been demonstrated that subjects can use information presented to several sites on the skin at the same time, implying an ability to attend to clearly suprathreshold stimuli presented simultaneously to more than a single location. In one study, subjects were presented with pairs of patterns consisting of up to 10 vibrators, contacting 10 different sites on the body, acti-

“…Taken together, these results indicate that if a particular communication system leads to good discrimination of tactile spatial patterns, it may also lead to good identification of such patterns. However, the fact that Cholewiak and Craig (1984) found an imperfect match between discrimination and identification performance when rank ordered across several conditions argues for some caution in assuming that improved discriminability automatically leads to improved identifiability.…”

Section: Discussionmentioning

confidence: 99%

A comparison of discrimination and identification of vibrotactile patterns

Horner

Craig

1989

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Both discrimination and identification tasks have been used to assess subjects' abilities to perceive vibratory spatial patterns presented to the skin. The present study examined discrimination and identification performance under comparable conditions. In Experiment 1, subjects attempted to discriminate a pair of patterns on some blocks of trials and to identify both members of a pair on other blocks. For both tasks, the time between the members of the pair was varied. Discrimination performance could be predicted accurately from identification data. Analysis of performance on identification trials indicated that subjects used discriminability information to identify pairs. In Experiment 2, discrimination and identification were compared when the temporal separation between patterns was fixed and a masking stimulus followed each pattern after a variable delay. Results suggest that temporal masking, rather than the time available for processing pattern information, is the major limitation in both discrimination and identification of sequences of tactile patterns.The skin rarely processes a single pattern isolated temporally from other patterns. The hands and fingers explore the surface of an object by moving across successive surface areas. Thus, sequences of tactile, spatial patterns are produced. Sometimes, a tactile surface is explored to locate the place where the surface changes, which may be viewed as a discrimination task: Are successive patterns the same or different? At other times, a surface is explored to reach a decision about what is being felt, an identification task. These two measures of performance-discrimination and identification-have been examined in a number of studies using vibratory spatial patterns (discrimination-