Grasping and perception are both affected by irrelevant information and secondary tasks: new evidence from the Garner paradigm

Abstract

In their Perception-Action Model (PAM), Goodale and Milner (1992) proposed functionally independent and encapsulated processing of visual information for action and perception. In this context, they postulated that visual input for action is processed in an automatized and analytic manner, which renders visuomotor behaviour immune to perceptual interferences or multitasking costs due to sharing of cognitive resources. Here, we investigate the well-known Garner Interference effect under dual-and single-task conditions in its classic perceptual form as well as in grasping. Garner Interference arises when stimuli are classified along a relevant dimension (e.g., their length), while another irrelevant dimension (e.g., their width) has to be ignored. In the present study, participants were presented with differently sized rectangular objects and either grasped them or classified them as long or short via button-presses. We found classical Garner Interference effects in perception as expressed in prolonged reaction times when variations occurred also in the irrelevant object dimension. While reaction times during grasping were not susceptible to Garner Interference, effects were observed in a number of measures that reflect grasping accuracy (i.e., poorer adjustment of grip aperture to object size, prolonged adjustment times, and increased variability of the maximum hand opening when irrelevant object dimensions were varied). In addition, multitasking costs occurred in both perception and action tasks. Thus, our findings challenge the assumption of automaticity in visuomotor behaviour as proposed by the PAM.

The Role of Haptic Expectations in Reaching to Grasp: From Pantomime to Natural Grasps and Back Again

“…In normally sighted individuals, grasping resists a number of effects that influence perceptual judgments: grasp aperture resists the target size-distorting influence of illusory backgrounds (e.g, Whitwell et al, 2016Whitwell et al, , 2018Carther-Krone et al, 2020;Navon and Ganel, 2020;Smeets et al, 2020; but see Kopiske et al, 2016); it resists Weber's Law, failing to show a positive relationship between precision and stimulus size (e.g., Ganel et al, 2008;Holmes et al, 2011;Heath et al, 2012;Ozana and Ganel, 2018b; but see Foster and Franz, 2013); and grasp preparation time is not prolonged in the filtering condition of the Garner interference paradigm, in which choice-response times increase when both the relevant and irrelevant dimensions of the target are varied (e.g., Goodale, 2003, 2014;Eloka et al, 2015;Freud and Ganel, 2015;Ozana and Ganel, 2018a; but see Löhr-Limpens et al, 2020).…”

Grasping Discriminates between Object Sizes Less Not More Accurately than the Perceptual System

“…Finally, Singhal et al [20] showed that a more general cognitive phenomenon, namely the finding that the concurrent execution of two tasks creates performance costs for at least one of the two tasks, reliably occurs in tasks that can be assigned to the perceptual system but is much less prominent in tasks assigned to the visuomotor system. However, all these approaches have been met with counter-evidence and are currently bogged down in controversy [21,22,23,24,25,26,27,28,29].…”