Beyond vision: The Müller-Lyer illusion reveals geometric biases in passive touch and haptic exploration

Gwynne, Louisa, Ernst, Fiona, Lenatti, Carmen and Tamè, Luigi 2026. Beyond vision: The Müller-Lyer illusion reveals geometric biases in passive touch and haptic exploration. Neuropsychologia 231 , 109549. 10.1016/j.neuropsychologia.2026.109549

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Abstract

The Müller-Lyer Illusion has been extensively studied in the visual modality and, to a lesser extent, in haptic exploration. However, with the exception of an early descriptive study in the 1930s, no reports have investigated the illusion during passive tactile stimulation. Previous research uses the terms “tactile” and “haptic” interchangeably, despite exclusively examining active exploration. The present study investigated whether the illusion emerges during passive tactile stimulation, and whether its expression differs from that observed during haptic exploration with sensorimotor engagement. Twenty participants completed a manual bisection task of Müller-Lyer stimuli in a haptic exploratory or passive tactile form. Reliable illusory bias was observed in the haptic condition, with midpoint judgments shifted towards the arrow wings. Notably, this effect was mediated by the effector, with stronger bias when responses were made using the right index finger. In the tactile condition, a configuration-dependent effect emerged, in that distally pointing arrows on the forearm elicited significant illusory midpoint shifts, whereas proximal and neutral configurations did not. These findings show that the Müller-Lyer illusion arises under passive tactile stimulation, specifically, we show that contextual geometric cues bias somatosensory spatial perception in the absence of voluntary exploration.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Healthcare Sciences
Publisher:	Elsevier
ISSN:	0028-3932
Date of First Compliant Deposit:	21 July 2026
Date of Acceptance:	13 July 2026
Last Modified:	21 Jul 2026 11:15
URI:	https://orca.cardiff.ac.uk/id/eprint/188375

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