title: Fourier decomposition of spatial localization errors reveals an idiotropic dominance of an internal model of gravity.
abstract: Given its conspicuous nature, gravity has been acknowledged by several research lines as a prime factor in structuring the spatial perception of one's environment. One such line of enquiry has focused on errors in spatial localization aimed at the vanishing location of moving objects - it has been systematically reported that humans mislocalize spatial positions forward, in the direction of motion (representational momentum) and downward in the direction of gravity (representational gravity). Moreover, spatial localization errors were found to evolve dynamically with time in a pattern congruent with an anticipated trajectory (representational trajectory). The present study attempts to ascertain the degree to which vestibular information plays a role in these phenomena. Human observers performed a spatial localization task while tilted to varying degrees and referring to the vanishing locations of targets moving along several directions. A Fourier decomposition of the obtained spatial localization errors revealed that although spatial errors were increased "downward" mainly along the body's longitudinal axis (idiotropic dominance), the degree of misalignment between the latter and physical gravity modulated the time course of the localization responses. This pattern is surmised to reflect increased uncertainty about the internal model when faced with conflicting cues regarding the perceived "downward" direction.
authors.affiliation: Institute of Cognitive Psychology, University of Coimbra, Portugal. nuno_desateixeira@fpce.uc.pt
authors.forename: Nuno Alexandre
authors.initials: NA
authors.lastname: De Sá Teixeira
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D005260:Female; D006112:Gravitation; D006801:Humans; D008297:Male; D008954:Models, Biological; D009039:Motion Perception / Q000502:physiology*; D010775:Photic Stimulation; D011601:Psychophysics; D013028:Space Perception / Q000502:physiology*; D055815:Young Adult