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Amanda Elam, Catherine Norris, Greer Prettyman, Ray Lefco, Frank Durgin; Failure of spontaneous phase locking for side-by-side walkers in visual contact. Journal of Vision 2016;16(12):1364. doi: 10.1167/16.12.1364.
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© ARVO (1962-2015); The Authors (2016-present)
Do paired walkers with similar stepping frequencies spontaneously synchronize their steps when in visual contact? To examine this question, pairs of students who did not know each other participated in an experiment ostensibly about effects of fatigue on performance. The natural gait ratio (Durgin, Reed, & Tigue, 2007) of each participant was calculated based on a brief period of walking down a measured hallway. Participants were then asked to walk on side-by-side treadmills for five minutes. The speeds of the two treadmills were set based on the measured gait ratios such that the expected stepping frequencies of the two walkers were either similar ("easy" condition) or separated by 12% ("hard" condition). Crossed with this manipulation, instructions were given to half of the pairs of walkers to try to synchronize their steps (no instruction was given to the other half of the walker pairs). To quantify phase locking, we measured the proportion of time participants' steps were within 90° of phase of each other. This value was rescaled assuming that time spent accidentally within 90° of phase would be equal to time spent more than 90° out of phase. Under instructions to synchronize steps, the median percent time spent in phase was 94% (M = 77%) in the easy condition and 28% (M = 36%) in the hard condition. Without explicit instruction, however, spontaneous phase locking was rare in the easy condition (median: 17%; M = 14%), and almost non-existent in the hard condition (median: 0%; M = 1%). The infrequency of phase-locking is surprising. Video-recordings of paired walkers on public walkways suggest that spontaneous synchronization is frequent (60%) when walkers have similar stepping frequencies (Hajnal & Durgin, unpublished data). Given that our participants didn't know each other, social factors may contribute to the emergence (or avoidance) of spontaneous phase-locking.
Meeting abstract presented at VSS 2016
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