Brain and Cognition 59 (2005) 287–291 www.elsevier.com/locate/b&c 0278-2626/$ - see front matter  2005 Elsevier Inc. All rights reserved. doi:10.1016/j.bandc.2005.07.006 Brief communication Visual cues and perceived reachability Carl Gabbard ¤ , Diala Ammar Texas A&M University, USA Accepted 6 July 2005 Available online 9 September 2005 Abstract A rather consistent Wnding in studies of perceived (imagined) compared to actual movement in a reaching paradigm is the ten- dency to overestimate at midline. Explanations of such behavior have focused primarily on perceptions of postural constraints and the notion that individuals calibrate reachability in reference to multiple degrees of freedom, also known as the whole-body explana- tion. The present study examined the role of visual information in the form of binocular and monocular cues in perceived reachabil- ity. Right-handed participants judged the reachability of visual targets at midline with both eyes open, dominant eye occluded, and the non-dominant eye covered. Results indicated that participants were relatively accurate with condition responses not being signiW- cantly diVerent in regard to total error. Analysis of the direction of error (mean bias) revealed eVective accuracy across conditions with only a marginal distinction between monocular and binocular conditions. Therefore, within the task conditions of this experi- ment, it appears that binocular and monocular cues provide suYcient visual information for eVective judgments of perceived reach at midline.  2005 Elsevier Inc. All rights reserved. Keywords: Imagined movements; Perceived reachability; Reaching; Visual cues 1. Introduction Understanding the perception to action dynamics involved in reaching and grasping an object constitutes one of most mystifying issues in motor behavior research. These actions require a complex set of percep- tual to motor transformations. One of the initial steps is to derive a perceptual estimation of the object’s distance and location relative to the actor. A relatively common Wnding among studies of perceptual estimates (imag- ined) versus actual movement is the observation of an overestimation bias in reachability at midline positions (Bootsma, Bakker, Snippenberg, & Tdlohreg, 1992; Fischer, 2000; Mark et al., 1997). That is, individuals exhibit a general tendency to perceive that they can reach objects that are actually out of grasp. Explana- tions for this bias have focused predominately on issues related to perceived postural constraints (Carello, Grosofsky, Reichel, Soloan, & Turvey, 1989; Heft, 1993; Robinovitch, 1998) and the general notion that individu- als ‘preconceive’ and calibrate such actions via ‘whole body engagement’ (e.g., Rochat & Wraga, 1997). Data from our laboratory (Gabbard, Ammar, & Rodrigues, 2005) and a report by Fischer (2005) contends that no single-factor accounts for reachability estimates. That is, it would appear that perceived reachability is a complex phenomenon based on one’s perceived ability and per- ceived demands of the task. However, one consideration that has been given rela- tively little attention is the role of visual information in the form of binocular and monocular cues. Obviously vision plays a key role in reaching behavior—that is, via transport of the positioning of the hand through space, to achieving a suitable grasp posture to pick up the object. Kinematic studies in general have found that bin- ocular information is particularly important for the * Corresponding author. Fax: +1 979 847 8987. E-mail address: c-gabbard@tamu.edu (C. Gabbard).