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Abstract:
It has been proposed that the perception of 'up' is constructed by the brain as a vector sum; combining estimates of the visual vertical, the orientation of gravity, and the prior knowledge that 'up' is usually above our heads - called the idiotropic vector (Mittelstaedt, 1983). In a more recent study (Dyde et al., 2006), the weighting of the respective cues was found to be consistent with predictions from Bayesian accounts of perception. However, a study conducted in partial gravity (De Winkel et al., 2012) has shown that visual cues were discarded entirely, and that the contributions of the idiotropic vector and gravitational vertical have a dichotomous nature under conditions of reduced gravity. These findings suggest that the analogy of a vector sum does not always apply. Here we investigate how the perception of vertical is affected by intersensory discrepancies. We presented our participants with an array of visual and inertial orientation stimuli using a motion platform and a newly developed augmented reality system, and tasked them to indicate the perceived vertical. We will discuss the study's findings, and their implications for theories on orientation perception.