Is judging time-to-contact based on 'tau'?

J. B J Smeets*, Eli Brenner, Sonia Trébuchet, Daniel R. Mestre

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review


An investigation was undertaken into whether judgments of time-to-contact between a laterally moving object and a bar are based on the direct perception of an optical variable (tau), or on the ratio between the perceived distance and perceived velocity of the object. A moving background was used to induce changes in the perceived velocities without changing the optical variables that specify time-to-contact. Background motion induced large systematic errors in the estimated time-to-contact. It is concluded that the judgment of time-to-contact is primarily based on the ratio between the perceived distance and the perceived velocity, and not on tau.

Original languageEnglish
Pages (from-to)583-590
Number of pages8
Issue number5
Publication statusPublished - 1996


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