Effect of different pupil to eye size ratios on tonic immobility in chickens

Abstract

Seven simulated eyes with varying pupil size to eye ratios were tested for their effects on the duration of tonic immobility. A pair of eyes with a ratio of approximately 11/20 mm was the only configuration which produced reliable increases in response duration. The results were discussed as they relate to the possible role of eye contact in predator-prey encounters. © 1976, The Psychonomic Society, Inc. All rights reserved.