The role of object affordances and center of gravity in eye movements toward isolated daily-life objects

TLDR

The study examined whether low‑level visual cues or high‑level affordances guide eye landing positions on isolated daily‑life objects. Participants performed saccades to peripherally presented photographs of graspable objects in two experiments, with low‑level effects defined as attraction to the center of gravity or absolute center and high‑level effects defined as visuomotor priming by affordances, while objects were rotated to separate graspable and action‑performing parts. Early saccades landed near the center of gravity/center, showing no bias toward graspable or action‑performing parts, whereas longer‑latency saccades and refixations were biased toward the action‑performing part, indicating that high‑level affordance effects, not low‑level shape or saliency, guide eye movements after a delay.

Abstract

The purpose of the current study was to investigate to what extent low-level versus high-level effects determine where the eyes land on isolated daily-life objects. We operationalized low-level effects as eye movements toward an object's center of gravity (CoG) or the absolute object center (OC) and high-level effects as visuomotor priming by object affordances. In two experiments, we asked participants to make saccades toward peripherally presented photographs of graspable objects (e.g., a hammer) and to either categorize them (Experiment 1) or to discriminate them from visually matched nonobjects (Experiment 2). Objects were rotated such that their graspable part (e.g., the hammer's handle) pointed toward either the left or the right whereas their action-performing part (e.g., the hammer's head) pointed toward the other side. We found that early-triggered saccades were neither biased toward the object's graspable part nor toward its action-performing part. Instead, participants' eyes landed near the CoG/OC. Only longer-latency initial saccades and refixations were subject to high-level influences, being significantly biased toward the object's action-performing part. Our comparison with eye movements toward visually matched nonobjects revealed that the latter was not merely the consequence of a low-level effect of shape, texture, asymmetry, or saliency. Instead, we interpret it as a higher-level, object-based affordance effect that requires time, and to some extent also foveation, in order to build up and to overcome default saccadic-programming mechanisms.