There Is No Word Superiority Effect In Peripheral Vision

摘要

When using the fovea, context plays an important role in reading. This includes the general gist of a story (Potter et al., 1980), the words within sentences (e.g. Forster, 1970; Morton, 1964, among others), and the letters within words (McClelland & Rumelhart, 1981; Reicher, 1969; Rumelhart & McClelland, 1982; Wheeler, 1970). This latter is known as the Reicher-Wheeler effect, or the word-superiority effect (WSE). Specifically, the probability of correctly identifying a letter is greater when that letter is part of a word than when it is presented alone or as part of a random letter sequence. It is less clear whether context, at least at the sentence level, plays an important role in reading with peripheral vision. For example, Fine et al. (1999) showed that the benefits derived from context at 5 deg eccentricity were either equal to or greater than the benefits derived from context when reading with the fovea, and Fine and Peli (1996) found no difference in context gain between a group of patients with central field loss and a group of age-matched subjects with normal vision. However, Latham and Whitaker (1996) have and Chung et al. (1998) reported reduced or no benefit from sentence context in the periphery. To my knowledge, the role of word context on letter identification has not been studied in the periphery. That is the goal of the current study. In a recent study (Fine, 1999), I found that subjects were better able to identify letters presented at 5 deg in the lateral visual field when they were part of a word (bat) than when they were surrounded by x's (xax), or when they were part of a non-word sequence (saq). This supports the idea that words provide some benefit to letter identification. However, it did not allow me to conclude that there was a word superiority effect in peripheral retina because single letters were not tested in that experiment. In the current experiment, subjects identified single letters, 3-letter words, and 3-letter non-word sequences (trigrams). The stimuli were displayed so that the center letter was at either 5 deg or at 0 deg. The threshold stimulus duration (SD) necessary to correctly identify the letters was used as the dependent measure. If there is a word superiority effect, threshold SD will be shorter for words than for either letters or trigrams.