Motion signal strength and body orientation: which way is ‘down’ for representational gravity?

• Autor(a) principal: Loureiro, Ana Raquel Pereira
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/34904
• topic: Spatial orientation; Representational gravity; Representational momentum; Idiotropic vector; Strength of the motion signal

The perceived offset of a moving target has been shown to be displaced forward, in the direction of motion (Representational Momentum; RM) and downward, in the direction of gravity (Representational Gravity; RG). Regarding RG, available evidence suggests that the ‘downward’ direction is chiefly determined by the orientation of the body’s main axis (idiotropic vector). However, a previous study reports increased displacements along gravity’s direction irrespective of the participants’ body orientation. These disparate reports might be accounted for by several differences between the methodologies used, prominently the type of motion displays – smooth or apparent motion –, known to significantly modulate spatial localization judgements. To clarify this issue, we report the outcomes of one experiment where strength of the motion signal (smooth vs apparent) was factorially crossed with participants’ body position relative to the vertical (upright vs left lateral decubitus) with a standard spatial localization task (using a trackball). Results reveal RG to be attached to the idiotropic vector and to be unaffected by vestibular signals, with motion type affecting the magnitude, but not the direction, of spatial displacements.