Abstract
Goals: When determining the direction of gravitational upright we depend more on visual signals from the external environment than we do on vestibular and proprioceptive inputs about the orientation of the body. For example, a vertical rod surrounded by a tilted frame will appear tilted in the opposite direction of the frame, even when are we in an upright posture. Given that covert transient attention enhances the representation of visual signals and alters the appearance of stimuli, we examined whether transient attention also enhances the influence of the visual environment (frame) on perceived upright (rod).
Methods: Observers determined the orientation of a tilted rod surrounded by a tilted frame presented 8o to the left or right of fixation. To engage attention, a 50 ms cue appeared to the left or right of fixation where the stimulus display (rod and frame) would appear. We compared performance with a neutral cue that appeared in the central region of the display. Following a brief ISI (50 ms), the rod and frame appeared on the left or right of fixation for 100 ms.
Results & Discussion: Observers perceived the orientation of the rod as a function of the frame to an increased extent in valid cue trials compared to neutral cue trials, as reflected by a significant reduction in the accuracy of their rod orientation judgments. These results indicate that attention enhances the influence of visual context on perceived upright, causing observers to see the rod as even more tilted in the opposite direction of the frame than it physically is. These findings further suggest that attention increases the degree to which observers favor visual input over vestibular and proprioceptive inputs when determining which way is “up.”
This work was supported by a grant from the National Institute of Health awarded to Marisa Carrasco (R01 EY016200-01A2)