Academic journal article Attention, Perception and Psychophysics

Tactile Search for Change Has Less Memory Than Visual Search for Change

Academic journal article Attention, Perception and Psychophysics

Tactile Search for Change Has Less Memory Than Visual Search for Change

Article excerpt

Published online: 28 February 2015

# The Psychonomic Society, Inc. 2015

Abstract Haptic perception of a 2D image is thought to make heavy demands on working memory. During active exploration, humans need to store the latest local sensory information and integrate it with kinesthetic information from hand and finger locations in order to generate a coherent perception. This tactile integration has not been studied as extensively as visual shape integration. In the current study, we compared working-memory capacity for tactile exploration to that of visual exploration as measured in change-detection tasks. We found smaller memory capacity during tactile exploration (approximately 1 item) compared with visual exploration (2-10 items). These differences generalized to position memory and could not be attributed to insufficient stimulus-exposure durations, acuity differences between modalities, or uncertainty over the position of items. This low capacity for tactile memory suggests that the haptic system is almost amnesic when outside the fingertips and that there is little or no cross-position integration.

Keywords Active touch . Visual search . Change detection . Working memory

It is known that 2D images that are immediately interpretable by sight are not easily recognized by touch (Heller, 1989; Kennedy & Fox, 1977; Lederman, Klatzky, Chataway, & Summers, 1990; Magee & Kennedy, 1980). Loomis, Klatzky, and Lederman (1991) have offered several explanations for the relative disadvantage of tactile picture perception compared to visual perception. For example, the tactile field of view is narrower than it is for vision, even with the use of multiple fingers (Loomis et al., 1991). Temporal and spatial acuity also is poorer in touch than vision (Loomis & Lederman, 1986). Uncertainty and distortion associated with the kinesthetic monitoring of the hand and fingers seems to be greater compared with the eyes (Balakrishnan, Klatzky, Loomis, & Lederman, 1989; Klatzky & Lederman, 1987). Finally, some of the stimulus materials derived from visual studies may be less familiar in terms of touch (Heller, 1989;Kennedy,2000;Kennedy& Fox, 1977;Ledermanetal.,1990).

In addition to these differences in processing, there are other possible limitations associated with higher-order processing related to working memory that enable perceptual integration over time to build up a coherent perception (Hochberg, 1986). Because tactile perception is normally believed to rely more on sequential exploration and local sampling than on vision, the subject must rely more on working memory. Working memory "stores" the current sensory information and updates and integrates that information with the kinesthetic information derived from the hand and fingers with every new sensory movement. The capacity of tactile working memory has not been studied as extensively as that of visual memory (Gallace &Spence,2009; Hill & Bliss, 1968). In particular, research on visual sampling during active exploratory processes (e.g., saccadic eye movements and visual searches) suggests that humans can accumulate an item memory across eye movements that equals working-memory capacity (approximately 4 to 7 items; e.g., Irwin, 1991; Irwin, 1992a; Irwin & Gordon, 1998). An increasing number of research studies have suggested that humans can hold a fairly limited number of items in memory for visual integrationacrosssearchbehavior.However,a number of questions remain. What about tactile integration? How many items are held during an active tactile search process? How much information is made available for the higher-order sensory-motor integration process resulting in a coherent perception? Is it possible to show that there is little or no integration across hand movements to account for the relative disadvantage of 2D tactual picture perception compared to vision?

To answer these questions, we assessed the amount of information that can be held in working memory across sensory movements during active tactile scanning and compared it with visual memory capacity under similar circumstances. …

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