Perceived Reachability in Single- and Multiple-Degree-of-Freedom Workspaces

Abstract

In comparisons of perceived (imagined) and actual reaches, investigators consistently find a tendency to overestimate. A primary explanation for that phenomenon is that individuals reach as a "whole-body engagement" involving multiple degrees of freedom (m-df). The authors examined right-handers (N = 28) in 1-df and m-df workspaces by having them judge the reachability of targets at midline, right, and left visual fields. Response profiles were similar for total error. Both conditions reflected an overestimation bias, although the bias was significantly greater in the m-df condition. Midline responses differed (greater overestimation) from those of right and left visual fields, which were similar. Although the authors would have predicted better performance in the m-df condition, it seems plausible that if individuals think in terms of m-df, they may feel more confident in that condition and thereby exhibit greater overestimation. Furthermore, the authors speculate that the reduced bias at the side fields may be attributed to a more conservative strategy based in part on perceived reach constraints.

Effect of visuomotor calibration and uncertainty on the perception of peripersonal space

“…Concerning the perceptual task, reachability judgments slightly overestimated actual action capabilities (23.8 mm on average, first block of trials), confirming the results obtained in previous studies (Bootsma et al, 1992;Carello et al, 1989;Coello & Iwanow, 2006;Fischer, 2000;Gabbard et al, 2006;Rochat & Wraga, 1997). In these studies, a tendency toward overestimation was reported-in particular, when estimates of reachability were provided in darkness or in the presence of postural constraints (as in the present study).…”

“…Some previous data support this interpretation by showing that increasing uncertainty in a sensorimotor task affects perceptual judgments of object properties (Ernst & Banks, 2002), as well as perceptual learning (Barthelmé & Mamassian, 2009;Shibata, Yamagishi, Ishii, & Kawato, 2009). In the present experiment, the induced discrepancy between visual and motor-related information may then have been concurrently perceived as a sudden increase of the variability of the visuomotor system, resulting in a reduction of the confidence attributed to the sensorimotor anticipatory processes (Gabbard et al, 2006;Gabbard et al, 2005). Modifying the state of confidence may have subsequently influenced the perception of reachable space, inducing a conservative strategy when reachability estimates were provided.…”

“…Although this remained unnoticed by the participants, this alteration of the movement-target correspondence may have been interpreted as an increased variability of the visuomotor system, leading to a conservative, yet unconscious, strategy affecting the visual perception of reachability (Fajen, 2005;Gabbard et al, 2006;Gabbard, Ammar, & Rodrigues, 2005). Some previous data support this interpretation by showing that increasing uncertainty in a sensorimotor task affects perceptual judgments of object properties (Ernst & Banks, 2002), as well as perceptual learning (Barthelmé & Mamassian, 2009;Shibata, Yamagishi, Ishii, & Kawato, 2009).…”

“…In the past, many studies have shown that people are quite accurate in visually delimiting their peripersonal space (e.g., Bootsma, Bakker, van Snippenberg, & Tdlohreg, 1992;Bourgeois & Coello, 2009;Carello et al, 1989;Coello & Iwanow, 2006;Fischer, 2000;Gabbard, Ammar, & Lee, 2006;Rochat & Wraga, 1997), although perceptual estimates of reachability have been found to be influenced by environmental context (Coello & Iwanow, 2006), emotional state (Kennedy, Gläscher, Tyszka, & Adolphs, 2009), and postural constraints (Fischer, 2000;Gabbard, Cordova, & Lee, 2007;Rochat & Wraga 1997), as well as mental or neurological illness (Coello & Delevoye-Turrell, 2007;Delevoye-Turrell, Vienne, & Coello, 2011).…”

Children's Visual Processing of Egocentric Cues in Action Planning for Reach

“…The second key finding of children's overestimation supports previous studies showing that children in general overestimate in real time (e.g., Gabbard, Ammar, & Lee, 2006;Gabbard, Cacola, & Cordova, 2008, 2009a, 2009bGabbard, Cordova, & Ammar, 2007;Gabbard, Cordova, et al, 2009;Rochat, 1995;Schwebel & Plumert, 1999). Our mean bias data support this general observation and show that children, compared with adults, significantly overestimate as delay increases.…”