CHARACTERIZING THE PROCESSING UNITS OF READING Effects of Intra- and Interword Spaces in a Letter Detection Task
Alice F. Healy University of Colorado
Gary L. Conboy University of Colorado
Adam Drewnowski University of Michigan
In a letter detection experiment in which asterisks or blank spaces were inserted between characters in continuous text, participants made significantly fewer errors when the test word subtended a larger visual angle. In a second experiment, the interword space before the test word the was found to be more critical for unit formation than the space after the. These results suggest that the size of' the processing units used by readers depends on visual angle and that the reading units for frequent function words such as the extend beyond the word itself, include the interword space, and are influenced more by familiarity than by linguistic function. These findings are discussed in terms of the notions of cognitive module and input system proposed by Fodor ( 1983).
A fundamental question for any model of the reading process is what is the type and size of the units that are used for the processing of written text. In the present study we investigated this question by manipulating the spaces surrounding potential units. Following Corcoran ( 1966), we have developed a simple letter detection task in which participants are asked to read a passage of text and circle every instance of a target letter (e.g., the letter t). We have found that participants make more detection errors on very common words, such as the, than on rare words, such as thy ( Healy, 1976, 1980). The pattern of errors is further determined by the structure of the search passage ( Drewnowski & Healy, 1977) and by the