Abstract
The ability to judge accurately whether or not an action can be accomplished successfully is critical for selecting appropriate response options that enable adaptive behaviors. Such affordance judgments are thought to rely on the perceived fit between environmental properties and knowledge of one's current physical capabilities. Little, however, is currently known about the ability of individuals to judge their own affordances following a stroke, or about the underlying neural mechanisms involved. To address these issues, we employed a signal detection approach to investigate the impact of left or right hemisphere injuries on judgments of whether a visual object was located within reach while remaining still (i.e., reachability). Regarding perceptual sensitivity and accuracy in judging reachability, there were no significant group differences between healthy controls (N = 29), right brain damaged (RBD, N = 17) and left brain damaged stroke patients (LBD, N = 17). However, while healthy controls and RBD patients demonstrated a negative response criterion and thus overestimated their reach capability, LBD patients' average response criterion converged to zero, indicating no judgment tendency. Critically, the LBD group's judgment tendency pattern is consistent with previous findings in this same sample on an affordance judgment task that required estimating whether the hand can fit through apertures (Randerath et al., 2018). Lesion analysis suggests that this loss of judgment tendency may be associated with damage to the left insula, the left parietal and middle temporal lobe. Based on these results, we propose that damage to the left ventro-dorsal stream disrupts the retrieval and processing of a stable criterion, leading to stronger reliance on intact on-line body-perceptive processes computed within the preserved bilateral dorsal network.
Highlights
Whether an action is suitable to be performed depends on reciprocity between properties of the environment and the subjects’ capabilities (Shaw et al, 1982; Turvey, 1992)
Based on previous results in a different affordance judgment task performed by the same participants, we expected significantly worse perceptual sensitivity in patient groups compared to healthy control subjects
Our present exploratory results support the idea that the study of affordance judgments in patients with functional deficits may help to unravel underlying mechanisms of affordance judgments and characteristic resilience of these mechanisms
Summary
Whether an action is suitable to be performed depends on reciprocity between properties of the environment and the subjects’ capabilities (Shaw et al, 1982; Turvey, 1992) Determining this is essential for action selection and subsequent adaptive behavior (Frey and Grafton, 2014). Gibson (1979) initially suggested that action is guided by the perception of affordances, in the sense that environmental properties directly offer information prompting for or affording certain actions. He termed the ability of perceiving action opportunities “affordance perception” (Gibson, 1977). Whilst navigating through our environment and interacting with objects, we are frequently confronted with the necessity to quickly decide whether we are capable to execute a particular action
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