Why a Y is not a V: a new look at the distinctive features of letters.

Although a feature detection theory of pattern recognition is consistent with many recent physiological and psychological findings, the specific rules governing the perception of the distinctive features of letters have not yet been determined. This article presente two new experimental procedures for determining these rules. Both procedures are demonstrated by the investigation of the specific rule involved in the perception of the letter attribute leg which distinguishes Y from V, F from C, and H from U. Whereas previous methods investigating the distinctive features of letters have focused primarily on archetypal letter forms, the present methods are based upon an investigation of ambiguous characters, those characters which can be assigned either of two letter labels with equal probability. One of these procedures allows for the investigation of these rules without the influence of external context, whereas the other allows for an investigation of the particular effects that external context can have on these rules.