A word superiority effect with nonorthographic acronyms: Testing for unitized visual codes

Letters in briefly presented masked letter strings were detected more accurately when the strings were three-consonant acronyms than when they were nonwords. In the absence of orthographic regularity, this word superiority effect (WSE) could not have depended on visual units correspond­ ing to familiar bigrams. Since rendering the acronyms visually unfamiliar by alternating the case of their constituent letters did not introduce the left-right scanning effects observed for non­ words, it is concluded that the processing of the acronyms did not depend on the formation of whole-word visual units. It is argued instead that the WSE resulted from the postlexical activa­ tion of associatively connected single-letter codes. Finally, the results of case-alternation, size­ alternation, and mixed-type-font experiments are interpreted in conjunction with the view that lexical access is based on both lowercase and uppercase letter recognition units for words and only uppercase letter recognition units for acronyms. In Reicher's (1969) tachistoscopic recognition para­ digm, the brief presentation of a test string (e.g., WORK) was preceded and followed by masking characters that interfered with the processing of the string. Subjects were then provided with two response alternatives (e.g., WORK-WORD). Their choice between the alternatives, which in the above example would indicate whether they had detected the presence of a K in the last letter of WORK, was better for strings that were words than for strings that were nonwords. This result, which has been termed the word superiority effect (WSE), indicates that tachistoscopic letter detection is facilitated by the activa­ tion of lexical entries for the test word. Carr and Pollatsek (1985) have recently proposed that the WSEresults from the formation ofnonvisual, whole­ word unitizing codes that "protect" the information in the briefly presented word from the effects of masking and memory loss. Evidence consistent with this hypothe­ sis has been reported by Hawkins, Reicher, Rogers, and Peterson (1976), who showed that letter detection was more accurate for standard response alternatives (e.g., WORD-WORK) than for phonologically identical re­ sponse alternatives (e.g., SITE-CITE). Another possibility is that the WSE could result from the formation of uni­ tized whole-word codes that are visual rather than phono­ logical. Experiments in which consecutive letters in a test string are presented in different cases (e.g., wOrK) are consistent with the hypothesis that higher order visual codes could mediate the WSE. Pollatsek, Well, and The research reported in this paper was supported by Grant MDA903­ 82-C-Q317from the Army Research Institute. We thank Mary LaLomia for preparing the computer programs used to conduct the experiments and analyze the data, and Edward O'Brien for his careful reading of the manuscript. Helga Noice is currently at Rutgers University. H. S. Hock's mailing address is Department of Psychology, Florida Atlantic University, Boca Raton, FL 33431. Schindler (1975) found that case alternation increased the time required for subjects to detect letter differences be­ tween pairs of words but not between pairs of orthographi­ cally irregular nonwords. Although these results showed that case alternation could affect lexical activation by ren­ dering words visually unfamiliar, McClelland (1976) found that the advantage of words over orthographically regular pseudowords was not affected by case alternation. This indicated that if visual unitization was responsible for the WSE, the units were smaller than the whole word. It is possible, however, that whole-word visual unitiza­ tion was not observed in McClelland's study because lexi­ cal activation based on whole-word visual codes was less efficient than lexical activation based on phonological codes (formed by the application of spelling-to-sound translation rules to the orthographically regular words). The purpose of the experiment reported in this paper was to determine whether a WSE could be obtained for the rapid, masked presentation of three-consonant acro­ nyms (e.g., NBC). There were two reasons why the use of these acronyms provided a strong test of the visual uniti­ zation hypothesis. First, their shortness and the con­ sistency with which they have been experienced in purely uppercase format increased the likelihood of the acro­ nyms' being recognized (i.e., their lexical entries acti­ vated) on the basis of whole-word visual units. Second, the absence ofvowels made it impossible for lexical acti­ vation to depend on whole-unit phonological codes formed via spelling-to-sound translation rules. In contrast, ortho­ graphically regular words are usually longer than acro­ nyms, the likelihood of recognizing them on the basis of whole-unit visual codes is decreased because they are ex­ perienced in different case formats (sometimes all upper­ case, sometimes all lowercase, sometimes with the first letter uppercase and the remaining letters lowercase), and they lend themselves to the formation ofunitized phono