Features for identification of uppercase and lowercase letters.

The determination of the visual features mediating letter identification has a long-standing history in cognitive science. Researchers have proposed many sets of letter features as important for letter identification, but no such sets have yet been derived directly from empirical data. In the study reported here, we applied the Bubbles technique to reveal directly which areas at five different spatial scales are efficient for the identification of lowercase and uppercase Arial letters. We provide the first empirical evidence that line terminations are the most important features for letter identification. We propose that these small features, represented at several spatial scales, help readers to discriminate among visually similar letters.