Perception & Psychophysics 1999,61 (7), 1384-1398 Intersensory conflict between vision and touch: The response modality dominates when precise, attention-riveting judgments are required MORTON A. HELLER Winston-Salem State University, Winston-Salem, North Carolina JEFFREY A. CALCATERRA Wright State University, Dayton, Ohio and SHAVONDA L. GREEN and LATONYA BROWN Winston-Salem State University, Winston-Salem, North Carolina In four experiments, reducing lenses were used to minifyvision and generate intersensory size con­ flicts between vision and touch. Subjects made size judgments, using either visual matching or haptic matching. In visual matching, the subjects chose from a set of visible squares that progressively in­ creased in size. In haptic matching, the subjects selected matches from an array of tangible wooden squares. In Experiment 1,it was found that neither sense dominated when subjects exposed to an in­ tersensory discrepancy made their size estimates by using either visual matching or haptic matching. Size judgments were nearly identical for conflict subjects making visual or haptic matches. Thus, matching modality did not matter in Experiment 1. In Experiment 2, it was found that subjects were influenced by the sight of their hands, which led to increases in the magnitude of their size judgments. Sight of the hands produced more accurate judgments, with subjects being better able to compensate for the illusory effects of the reducing lens. In two additional experiments, it was found thatwhen more precise judgments were required and subjects had to generate their own size estimates, the response modality dominated. Thus, vision dominated in Experiment 3, where size judgments derived from view­ inga metric ruler, whereas touch dominated in Experiment 4, where subjects made size estimates with a pincers posture of their hands. It is suggested that matching procedures are inadequate for assessing intersensory dominance relations. These results qualifythe position (Hershberger & Misceo, 1996)that the modality of size estimates influences the resolution of intersensory conflicts. Only when required to self-generate more precise judgments did subjects rely on one sense, either vision or touch. Thus, task and attentional requirements influence dominance relations, and vision does not invariably pre­ vail over touch. Researchers have long found that vision is dominant sense of vision and the sense of touch (Rock & Harris, over other modalities when conflicting information is 1967; Rock & Victor, 1964). The subjects in Rock's ex­ presented (e.g., Ryan, 1940, p. 687). Rock and his col­ periments felt a square through a cloth while looking at leagues reported an influential series ofexperiments dem­ it through a reducing lens, which minifies vision, and made onstrating visual dominance, given a conflict between the a single judgment about the size (or shape) ofthe stimu­ lus object. Rock reported that subjects generally relied on vision for their judgments, despite the fact that this yielded Preparation of this report and some of the research were supported nonveridical perception. These experiments have been in­ by NIH Grant 2 S06 RR-08040. Faith Heller provided helpful com­ fluential; they have prompted a great deal ofresearch and ments on an earlier version of this manuscript. Cindy Flynt assisted have convinced many people that vision is invariably dom­ with data collection and analyses. We are grateful to Richard Williams inant over touch. for advice about optics and optical measurements on the lens used in Experiments I and 2. Lester Krueger, Mark Hollins, and two anonymous The visual dominance literature has relied heavily on the reviewers made helpful comments on this manuscript. Correspondence discrepancy paradigm introduced by Rock and Victor concerning this article should be addressed to M. A. Heller, Depart­ (1964), which presupposes that subjects will assume that ment ofPsychology, Eastern Illinois University, 119 Physical Science they are feeling and seeing the same object. There is no real Bldg., 600 Lincoln Avenue, Charleston, IL 61920-3099 (e-mail: cfmah [email protected]). conflict between vision and touch ifwe look at one object and feel another. Rock and Victor used a variety ofresponse -r-Accepted by previous editor, Myron L. Braunstein measures in their study. Their subjects showed visual dom- Copyright 1999 Psychonomic Society, Inc. 1384 INTERSENSORY CONFLICT 1385 inance when making haptic matches, when drawing the in matching procedures is overloaded. Under many nor­ stimuli using sight, and when making visual matches. mal circumstances, people see their hands as they feel The Rock and Victor (1964) discrepancy paradigm objects (Heller, 1993) and this visual information may makes the assumption that subjects will have no difficulty be critical for the resolution of intersensory discrepan­ making accurate judgments about length with both vi­ cies. Thus, ifsubjects see their hands move in a direction sion and touch. However, things are not that simple, and that is counter to proprioception, most do not believe vi­ there are a number of reasons to doubt that subjects can sion (Heller, 1992). make comparably accurate simultaneous or sequential comparisons through both modalities (see Freides, 1974, Hershberger and Misceo's (1996) Study 1975). There are reports indicating that conditions ofde­ A recent, interesting report by Hershberger and Mis­ lay can influence haptic or cross-modal conditions more ceo (1996) is clearly relevant to the present issue. Hersh­ than they influence visual judgments (Abravanel, 1973; berger and Misceo used a variant of Rock and Victor's Cashdan, 1968; Cashdan & Zung, 1970; Zung, Butter, & (1964) paradigm and had subjects feel a square while Cashdan, 1974). Thus, memory demands could affect viewing it through a negative meniscus lens that halved resolution ofconflicts between vision and touch, because the size ofthe visual image. They reported that their sub­ the Rock and Harris (1967) discrepancy paradigm forces jects resolved the conflict between vision and touch in subjects to remember the stimulus experienced during favor oftouch, in haptic matching conditions. When vi­ the conflict trial. It is very possible that the results are sual matches were required, the subjects showed visual limited to differential memory skills for the senses ofvi­ dominance. When the data were examined on the first trial sion and touch. Other studies indicate that subjects have block, mean matching size varied with modality of the difficulty making size estimates with touch. Bartley match in discrepancy conditions (see Hershberger & Mis­ (1953) assumed that tactual judgments were generally ceo, 1996, Figure 2). Subjects making visual matches in modified by visual imagery and, also, that visual judg­ conflict conditions judged the stimuli to be slightly less ments ofsize were influenced by true distance. Schlater, than 3.5 cm (see Figure 2 in Hershberger & Misceo, 1996). Baker, and Wapner ( 1981) reported that perceived arm Visual controls (intramodal, vision alone, with vision of length was different when subjects were active or passive the standard stimuli through a reducing lens) judged the and actually shrank when subjects were passively touched. stimuli to be less than 2.5 ern. Note that, in the intersen­ These reports conflict with recent empirical evidence that sory conflict literature, the term control refers to condi­ suggests that people are able to make veridical, equiva­ tions in which there is no conflict. Conflict judgments lentjudgments oflength with vision and touch (Abravanel, with haptic matching (M greater than 4 em) were closer 1971; Teghtsoonian & Teghtsoonian, 1970). to the mean haptic control (haptic standards and haptic Recently, Power (1981) verified many ofRock's (Rock matches) judgments (M slightly greater than 4.5 em; see & Harris, 1967; Rock & Victor, 1964) findings and found Figure 2 in Hershberger & Misceo, 1996). that visual dominance occurs with a familiar object­ Also, in conflict conditions, subjects felt the squares namely, a coin. Furthermore, the phenomenon ofvisual (4,4.5,5,5.5, and 6 cm-) through an intervening cloth. dominance seemed robust, since it even occurred with the Hershberger and Misceo (1996) assumed that the pres­ bare hand. However, a strong lens tended to reduce the ence of the cloth made it impossible for subjects to see reliance on vision when the bare hand was visible (Power, their hands. However, one can readily see the movement 1980). Power used a lens that distorted the shape of vis­ of one's fingers through an intervening opaque cloth, ible objects, causing a square to appear rectangular. It is since motions ofthe cloth are visible (Heller, 1983). Con­ possible that this distortion was responsible for a shift in ceivably, individuals are then able to perceive a reduction apparent reliance on the senses of vision and touch. in finger span, using sight. If so, it is possible that changes There are limits to visual dominance. It is not evident in perceived size over trial block could reflect the influ­ with texture perception (Heller, 1982, 1989; Lederman ence ofthis knowledge ofminification, acquired through & Abbott, 1981) or when vision is blurry (Heller, 1983). vision, rather than the possible influence of haptics on Also, haptic dominance can occur in pattern perception resolution ofthe conflict. This possibility was examined when vision is manipulated by a mirror, rather than by a in Experiment 2 ofthe present study. lens (Heller, 1992).