Perceptual processing of adjacent and nonadjacent tactile nontargets

Abstract

Previous research has shown that subjects appear unable to restrict processing to a single finger and ignore a stimulus presented to an adjacent finger. Furthermore, the evidence suggests that, at least for moving stimuli, an adjacent nontarget is fully processed to the level of incipient response activation, The present study replicated and expanded upon these original findings. The results of Experiment 1 showed that an equally large response-competition effect occurred when the nontarget was presented to adjacent and nonadjacent fingers (on the same hand). The results of Experiment 2 showed that the effects observed in Experiment 1 (and in previous studies) were also obtained with stationary stimuli. Although small, there was some indication in the results of Experiment 2 that interference may dissipate more rapidly with distance with stationary stimuli. An additional finding was that interference effects were observed in both experiments with temporal separations between the target and nontarget of up to 100 msec. In Experiment 3, target and nontarget stimuli were presented to opposite hands. Although reduced, interference was still evident with target and nontarget stimuli presented to opposite hands. Varying the physical distance between hands did not produce any change in the amount of interference. The results suggest that the focus of attention on the skin extends nearly undiminished across the fingers of one hand and is not dependent upon the physical distance between sites of stimulation. 571A recent study by Evans and Craig (1991) indicated that subjects have difficulty focusing their attention on one finger and ignoring stimulation at an adjacent site. In this study, subjects were instructed to focus their attention on the left index fmger and to identify the direction of movement of the stimulus presented to that finger. A second stimulus, also moving, was presented to the middle finger, adjacent to the index finger. The stimuli moved in the same direction or in opposite directions. We reasoned that if subjects could restrict their attention to the target location, the presence of the nontarget would produce little, if any, interference. If, however, subjects are unable to restrict their attention to a single finger on one hand, then the direction of movement of the adjacent nontarget might interfere with target performance in a systematic fashion. Specifically, target performance might be interfered with when the direction of movement of the nontarget was opposite to that of the target. The results showed that when the target and nontarget moved in opposite directions, accuracy was reduced and response latencies (correct trials) This research was supported by Grant DC-00095 from the National Institutesof Health and was conducted while the first author was a visiting scholar in the Institute for the Study of Human Capabilities at Indiana University. The authors thank Roger P. Rhodes for his assistance in conducting these experiments. Reprint requests should be addressed to P. M. Evans, Department o...

Tactile selective attention and body posture: Assessing the multisensory contributions of vision and proprioception

“…Given the conflicting findings in previous research regarding people's ability to ignore tactile distractors presented to one hand while trying to respond to tactile targets presented to the other hand (e.g., Driver & Grossenbacher, 1996;Evans & Craig, 1991;Evans et al, 1992), our first experiment was conducted in order to determine whether participants would indeed be any slower (and/or less accurate) in making elevation discrimination responses to vibrotactile targets presented to one hand when conflicting vibrotactile distractors were presented to the opposite hand.…”

“…In a subsequent study, Evans, Craig, and Rinker (1992) used the same motion discrimination task to measure selective tactile attention between adjacent and nonadjacent fingers of the same and opposite hands. They reported similar interference effects whether the target and the distractor stimuli were presented to adjacent or nonadjacent fingers of the same hand, suggesting a relatively broad tuning of the attentional focus to the hand (i.e., perhaps reflecting a hand-centered attention effect).…”

“…In particular, it appears that an abstract frame of reference may be prevalent when combinations of stimuli are presented to a particular hand and all that varies is the relative orientation of the hand in space (e.g., Moscovitch & Behrmann, 1994;Rinker & Craig, 1994;Tinazzi et al, 2000). However, somatotopic coordinates (or even hand-centered attentional effects) determine performance under conditions in which the target and the distractor stimuli are presented to different hands (i.e., in bimanual stimulation conditions) and what varies is the relative position of the two hands in space (e.g., Evans & Craig, 1991;Evans et al, 1992;Röder et al, 2000).…”

“…Driver and Grossenbacher (1996) reported another study that also highlighted a significant role of distance in terms of an abstract frame of reference. They used a selective attention task, and therefore, their paradigm was more similar to that used by Evans et al (1992) than to that used by Lakatos and Shepard (1997). The participants in their study had to discriminate a target (single vs. double vibration) presented to the little finger of one hand, while ignoring a concurrent vibration (congruent or incongruent with respect to the target) presented to the little finger of the opposite hand.…”

“…Our first goal (in Experiments 1 and 2) was to test spatial selective attention in touch under conditions of unpredictable versus predictable target location. In the majority of previous studies (e.g., Driver & Grossenbacher, 1996;Evans & Craig, 1991;Evans et al, 1992;Rinker & Craig, 1994), target location was known to the participants in advance, and therefore, tactile selective attention may have been more effective. However, in most real-life situations involving haptic exploration, people use several fingers at the same time to search a surface for a given feature, without necessarily having any advance knowledge of which finger will first encounter the target.…”