Academic journal article Attention, Perception and Psychophysics

The Effect of Visual Magnification and Reduction on Perceived Hand Size

Academic journal article Attention, Perception and Psychophysics

The Effect of Visual Magnification and Reduction on Perceived Hand Size

Article excerpt

Published online: 14 February 2014

© Psychonomic Society, Inc. 2014

Abstract The aim of the present study was to clarify the mechanisms underlying body understanding by examining the impact of visual experience (magnification and reduction) on perception of hand size and neutral external objects (squares). Independent groups of participants were asked to look through a 2× magnification lens, a ½-× reduction lens, or a control UV filter and to make visual size judgments about square stimuli and their hands. In Experiment 1, participants used a measuring device with unmarked wooden slats orientated in horizontal and radial/vertical space for their visual judgments. In Experiment 2, participants used an upright frontal slat for visual length judgments of their hands to eliminate any potential foreshortening in viewing the measurement apparatus. The results from the two experiments demonstrate that participants significantly underestimated both the square stimuli and their hands when they viewed them under a reduction lens. While overestimation and underestimation of squares was found for females in Experiment 2, males generally underestimated the squares. However, overestimation was not seen when the participants viewed their hands under a magnification lens. Implications of these findings are discussed.

Keywords Haptics . Multisensory processing . Spatial cognition

Cognition, action, and embodiment

Understanding of one's body is an intricate and complex process, the mechanisms of which are debated in the current literature. Research examining individuals with certain types of brain damage indicates that people conceive of their bodies via a perceptual mechanism that is distinct from that used when viewing other, nonbody objects (e.g., Guariglia & Antonucci, 1992;Shontz,1969; Shontz & McNash, 1972). Reed and Farah (1995) demonstrated a dissociation between perception of body and nonbody objects in normal individ- uals. Further work suggests not only that people perceive biological entities differently than nonbiological entities, but also that human body perception differs from perception of other animate objects as well (Reed, Nyberg, & Grubb, 2012).

Issues of importance are how these mechanisms operate and how sensory input is perceived and integrated to form an individual's understanding of his/her body in space. A partic- ularly contentious and theoretically important issue is how many different body representation systems exist in human beings and what processes constitute our body understanding. Representation of the body is widely used to describe an individual's impression and sense of his/her body organiza- tion, its position in space, and its relation to objects in the environment (Berlucchi & Agliotti, 1997), although there is still much controversy about the interaction of processes that make up overall body understanding (Kammers, Mulder, de Vignemont, & Dijkerman, 2010).Forexample,isbodyrep- resentation purely haptic, or is there a separate visual repre- sentation? These are the questions that form the rationale for the experiments presented here.

Theories about body understanding can be divided into two major views: those that purport that body representation exists as a number of distinct systems that interact and integrate to form an individual's overall body experience and those that propose that a single body representation exists. One account of embodiment proposes that individuals have online and offline body representations (Carruthers, 2008). Online repre- sentations correspond to the body in real time as it navigates the environment, whereas offline representations are stable prototypes of our bodies in their common states, stored in long-term memory. In healthy individuals, these two repre- sentations are integrated, allowing people to have simultaneous knowledge about their bodies as objects, while also using their bodies to navigate the environ- ment in real time. …

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