title: Mental rotation of letters, body parts and scenes during whole-body tilt: role of a body-centered versus a gravitational reference frame.
abstract: It is known that in mental-rotation tasks, subjects mentally transform the displayed material until it appears "upright" and then make a judgment. Here we evaluate, by using three typical mental rotation tasks with different degrees of embodiment, whether "upright" is coded to a gravitational or egocentric reference frame, or a combination of both. Observers stood erect or were whole-body tilted by 60°, with their left ear down. In either posture, they saw stimuli presented at different orientation angles in their frontal plane: in condition LETTER, they judged whether the stimuli were normal or mirror-reversed letters, in condition HAND whether they represented a left or a right hand, and in condition SCENE whether a weapon laid left or right in front of a displayed person. Data confirm that reaction times are modulated by stimulus orientation angle, and the modulation curve in LETTER and HAND differs from that in SCENE. More importantly, during 60° body tilt, the modulation curve shifted 12° away from the gravitational towards the egocentric vertical reference; this shift was comparable in all three conditions and independent of the degree of embodiment. We conclude that mental rotation in all conditions relied on a similar spatial reference, which seems to be a weighted average of the gravitational and the egocentric vertical, with a higher weight given to the former.
authors: Institute of Physiology and Anatomy, German Sport University Cologne, Germany. Electronic address: Bock@dshs-koeln.de.
authors: Otmar L
authors: OL
authors: Bock
authors: Institute of Physiology and Anatomy, German Sport University Cologne, Germany. Electronic address: marc.dalecki@web.de.
authors: Marc
authors: M
authors: Dalecki
mesh_terms: D000328:Adult; D003867:Depth Perception; D005260:Female; D006112:Gravitation; D018594:Human Body; D006801:Humans; D008297:Male; D016011:Normal Distribution; D009949:Orientation; D010775:Photic Stimulation; D011187:Posture; D011930:Reaction Time; D012399:Rotation; D014785:Vision, Ocular; D014956:Writing; D055815:Young Adult
keywords: Body tilt; Cognitive processing; Embodiment; Mental rotation; Reference frame