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Pearl S. Guterman, Robert S. Allison, James E. Zacher; Effects of head orientation on the perceived tilt of a static line and 3D global motion.. Journal of Vision 2013;13(9):874. doi: https://doi.org/10.1167/13.9.874.
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© ARVO (1962-2015); The Authors (2016-present)
When the head is tilted an objectively vertical (or horizontal) line is typically perceived as tilted. We explored whether this shift occurs when viewing 3D global motion displays. Global motion is processed, in part, in cortical area MST, which is believed to be involved in multisensory integration and may facilitate the mapping of spatial reference frames. Thus, we hypothesized that observers may be less susceptible to these biases for global motion compared to line displays. Observers stood, and lay left and right side down, while viewing a static line or random-dot 3D global motion display. The line and motion direction were tilted 0°, ±5°, ±10°, ±15°, ±20°, and ±25° from the gravitational vertical, and in a separate block tilted from the horizontal. After each trial, observers indicated whether the tilt was clockwise or counterclockwise from the perceived vertical or horizontal with a button press. Psychometric functions were fit to the data and shifts in the point of subjective equality (PSE) were measured. These shifts were greater when lying on the side than standing. These shifts were biased in the direction of the head tilt, consistent with the so-called A-effect. However, contrary to an earlier study by De Vrijer, Medendorp, and Van Gisbergen (2008, J Neurophysiol, 99: 915–930) that found similar PSE shifts for lines and 2D planar motion, we found significantly larger shifts for the static line than 3D global motion. There was no appreciable difference between the shift magnitude in the tilt-from-vertical and horizontal conditions. Furthermore, the direction of motion (up/down, left/right) had no significant influence on the PSE. The results will be discussed in terms of the sensory integration of motion information in cortical areas.
Meeting abstract presented at VSS 2013
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