Effects of orientation on the identification of simple visual patterns.

Abstract

Strong and systematic effects of orientation on the identification of simple patterns were found. Two experiments revealed that errors of identification for alphanumeric characters increased approximately linearly with increased angular deviation from the standard upright orientation. Pattern recognition does not seem to proceed via the extraction of orientation-invariant features. Prior failures to discover systematic effects of orientation on the identification of simple patterns may have resulted from the use of reaction time as a dependent measure. As little as 15 ms of processing time may be sufficient to compensate fully for a 180.degree. rotation of a simple pattern in the experimental situation. Reaction time experiments seeking effects of orientation must be designed to detect effects of smaller magnitude than may have been previously anticipated.