Orientation-specific Masking of Letter Features

Abstract

THE ability to detect or resolve a target consisting of a briefly presented bar or grating is diminished by preceding or following it with a grating of similar orientation. This orientation-specific masking is maximal when target and mask have the same orientation and the impairing effect of the mask decreases monotonically with increases in the angular difference between target and mask, reaching half its peak value at a difference of about ±15° (refs. 1–4). These findings have generally been attributed to the properties of single cortical cells which seem to act as orientation analysers and which have been shown to possess similar angular bandwidth tuning^5–7. Such selective masking may be used to compile pattern feature lists and to elucidate their organization in the recognition of complex patterns⁸. But we know of no studies of selective masking of multi-attribute patterns. Accordingly, we have explored the feasibility of selectively masking orientational features of letters to produce predictable confusions in a typical pattern recognition task.