The Role of Preview Time in the Effect of The Müller-Lyer Illusion on Saccade Amplitude
(2024) Seeing and Acting Workshop: Functional and Neural Perspectives — Location: Coimbra, Portugal (27.September.2024)
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- Abstract
- The finding that visual recognition impairments can occur independently of deficits in visually-guided action has led to the view that visual processes split into two distinct pathways responding to the specific requirements of perception and action. While perception would compute objects’ metrics relative to the visual context, action would estimate the absolute metrics right before movement execution to ensure precision and avoid constant recalculation in a dynamic world. Actions should thus be insensitive to illusions induced by the visual context, regardless of object preview time. Experimental validation of this prediction has been debated due to divergent results in research on hand-object interactions. One issue concerns the motor system’s ability to correct the effect of such illusions as the hand reaches the object, contrary to immediate perception. To address this, we investigated saccadic eye movements, which can hardly be corrected once initiated. Notably, we measured the amplitude of saccades performed along a horizontal line embedded in Müller-Lyer illusion figures, while carefully controlling confounding factors such as the center of gravity of the wings. The saccade amplitude was modulated by the Müller-Lyer illusion, beyond what can be attributed to changes in the center of gravity. Furthermore, a short preview duration (50 ms) enhanced the illusion effect on saccade amplitude compared to a long preview duration (2000 ms). These results contradict the predictions of the perception-action model and suggest that, when correction possibilities are limited, the visual processes underlying action are sensitive to visual context and preview time.
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Geers, L., Doré-Mazars, K., & Andres, M. (2024). The Role of Preview Time in the Effect of The Müller-Lyer Illusion on Saccade Amplitude. Seeing and Acting Workshop: Functional and Neural Perspectives, Coimbra, Portugal. https://hdl.handle.net/2078.5/236944