September 2019
Volume 19, Issue 10
Open Access
Vision Sciences Society Annual Meeting Abstract  |   September 2019
Both optical expansion and depth information are used to control 2D pedestrian following
Author Affiliations & Notes
  • Gregory C Dachner
    Cognitive, Linguistic & Psychological Sciences, Brown University
  • William H Warren
    Cognitive, Linguistic & Psychological Sciences, Brown University
Journal of Vision September 2019, Vol.19, 178c. doi:https://doi.org/10.1167/19.10.178c
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      Gregory C Dachner, William H Warren; Both optical expansion and depth information are used to control 2D pedestrian following. Journal of Vision 2019;19(10):178c. doi: https://doi.org/10.1167/19.10.178c.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Collective motion in human crowds emerges from local interactions between individuals, in which pedestrian follows their near neighbors (Rio, Dachner, & Warren, PRSB, 2018). In previous work, we found that a follower’s speed and heading are controlled by nulling the optical expansion and angular velocity of a leader, depending on the leader’s position. This model explains following one neighbor (Dachner & Warren, VSS 2017; Bai & Warren, VSS 2018, 2019) and following crowds (Dachner & Warren, VSS 2018), based on visual information. However, our previous experiments isolated optical expansion and angular velocity, removing distance information. Here we add depth information (vergence, binocular disparity, declination angle from the horizon), and put it in conflict with optical expansion. 10 participants walked in a virtual environment while head position and orientation were recorded at 90 Hz. They were instructed to follow a virtual target (speckled pole, 40 cm diameter) that rested on a textured ground plane. The target appeared in three initial positions relative to the participant (0°, 30°, 60° from straight ahead), two initial distances (1m, 4m), and moved forward in the walking direction at 0.8 m/s. After 5 seconds, the pole changed its expansion rate, heading direction (+/− 35°), or both. Although its position and motion on the ground plane were consistent with its trajectory, the pole’s width expanded or contracted as if it changed speed (+/− 0.2 m/s). Participants changed speed in response to this expansion; this effect was significantly reduced by the inclusion of depth information (36% less compared to control, t(9)=3.77, p< 0.01). As well, head pitch angle indicated that participants centered their field of view at the target’s base. These results imply that following is controlled by both optical expansion and declination angle of neighbors. We plan to integrate this into our visual model of crowd behavior.

Acknowledgement: Supported by NSF BCS-1431406 & the Link Foundation Modeling, Simulation, and Training Program 
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