Reaching and grasping actions and their context shape the perception of object size Annalisa Bosco Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy $ Fabio Daniele Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy Department of Biomedical, Metabolic and Neuroscience Sciences, University of Modena and Reggio Emilia, Modena, Italy $ Patrizia Fattori Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy $ Humans frequently estimate the size of objects to grasp them. In fact, when performing an action, our perception is focused towards the visual properties of the object that enable us to successfully execute the action. However, the motor system is also able to influence perception, but only a few studies have reported evidence for action-induced visual perception modifications. Here, we aimed to look for a feature- specific perceptual modulation before and after a reaching or a grasping action. Human participants were instructed to either reach for or grasp two-dimensional bars of different size and to perform a size perceptual task before and after the action in two contexts: in one where they knew the subsequent type of movement and in the other where they did not know. We found significant modifications of perceived size of stimuli more pronounced after grasping than after reaching. The mere knowledge of the subsequent action type significantly affected the size perception before the movement execution, with consistent results in both manual and verbal reports. These data represent direct evidence that, in natural conditions without manipulation of visual information, the action type and the action context dynamically modulate size perception, by shaping it according to relevant information required to recognize and interact with objects. Introduction The perception and action relationship usually supports the idea that a primary goal of perception is action. In this framework, traditional information- processing perspectives aimed at defining motor re- sponse as separate from and consequent to perception. In the last years, several behavioral studies have shown evidence for an ‘‘action-modulated perception’’ mech- anism that automatically enhances relevant object features during action preparation (Bekkering & Neggers, 2002; Craighero, Fadiga, Rizzolatti, & Umilt ` a, 1999; Fagioli, Hommel, & Schubotz, 2007; Hannus, Cornelissen, Lindemann, & Bekkering, 2005). Several theories proposed a weighting mechanism for processing visual features of objects (Bundesen, 1990; Found & Muller, 1996; Muller, Reimann, & Krum- menacher, 2003; Wolfe, 1994). In this view, the cognitive system assigns weights to information that is particularly relevant, so that information belonging to the dimension with the highest weight is prioritized. According to the dimensional weighting theory pro- posed by Muller et al. (Muller, Heller, & Ziegler, 1995), the visual field is represented in separate maps, such as color, orientation and size. Saliency signals are sent from these maps to a master map of saliency that computes the sum of dimension-specific signals. For example, if the target-defining dimension in a visual search task is known in advance, participants can increase the weights of that dimension before the target presentation so that features can be processed more efficiently. The effect of motor preparation on visual perception has been extensively studied for the oculomotor system suggesting that, shortly before the actual execution of an eye movement, spatial perception greatly improves at the eye movement target location (Deubel & Schneider, 1996; Hoffman & Subramaniam, 1995; Citation: Bosco, A., Daniele, F., & Fattori, P. (2017). Reaching and grasping actions and their context shape the perception of object size. Journal of Vision, 17(12):10, 1–19, doi:10.1167/17.12.10. Journal of Vision (2017) 17(12):10, 1–19 1 doi: 10.1167/17.12.10 ISSN 1534-7362 Copyright 2017 The Authors Received April 11, 2017; published October 20, 2017 This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. Downloaded from jov.arvojournals.org on 05/25/2020