Feature analysis and the growth of a percept

Twelve trigrams divided into four sets, the members of each set varying systematically in the feature configuration at each letter position, were repeatedly exposed at brief durations in a random order to subjects who were asked to report after each exposure those letters that could be recognized with certainty. The set of three trigrams that had the same features for all letters in a given ordinal position was identified with fewer exposures than were necessary to permit identification of sets for which the featural characteristics varied within a spatial position. The results were interpreted as being consistent with a constructive model of letter recognition in which the observer tests hypotheses regarding the presence of a given letter based on the presence of relevant features in a spatial position.