Perception of letters, words, and nonwords.

Letter vs. word and word vs. nonword identification were compared, with redundancy adequately controlled. The processing time of the test stimulus was varied to provide a number of levels of correct performance. The first experiment showed that letters were recognized better when presented alone than when embedded in words. In the second experiment, the identification of letters in words did not differ from the identification of letters in nonwords. These results conflict with earlier findings that have shown that a letter is better identified in a word than in a nonword or presented alone. The differences in the experimental procedures indicate either that redundancy may not have been adequately controlled in the earlier studies or that some other process besides a perceptual one might account for the results. Recent experiments have demonstrated that a letter is more easily identified when it is presented in a word than when it is presented alone or in a sequence of unrelated letters (Reicher, 1969; Wheeler, 1970). These results were considered important because it was argued that redundancy could not be responsible for the effect. Redundancy or the knowledge of the constraints which characterize letter sequences in words can enhance identification by simply delimiting the set of possible response alternatives. Since Reicher's experimental procedure supposedly eliminates the contribution of redundancy, any word advantage is, therefore, taken as a pure perceptual, rather than decision, effect. In Reicher's (1969) paradigm,,5s are presented with either a letter, a word, or a nonword. Immediately after the stimulus flash, a visual noise mask is presented which covers the former stimulus position. Two letter alternatives, one of which appeared in the original stimulus and one of which is incorrect, are presented either 1 or 2 sec. before or after the test stimulus. To eliminate the operations of redundancy