An activation-verification model for letter and word recognition yielded predictions of two-alternative forced-choice performance for 864 individual stimuli that were either words, orthographically regular nonwords, or orthographically irregular nonwords. The encoding algorithm (programmed in APL) uses empirically determined confusion matrices to activate units in both an alphabetum and a lexicon. In general, predicted performance is enhanced when decisions are based on lexical information, because activity in the lexicon tends to constrain the identity of test letters more than the activity in the alphabetum. Thus, the model predicts large advantages of words over irregular nonwords, and smaller advantages of words over regular nonwords. The predicted differences are close to those obtained in a number of experiments and clearly demonstrate that the effects of manipulating lexicality and orthography can be predicted on the basis of lexical constraint alone. Furthermore, within each class (word, regular nonword, irregular nonword) there are significant correlations between the simulated and obtained performance on individual items. Our activation-verification model is contrasted with McClelland and Rumelhart's (1981) interactive activation model.

Current models of fluent reading often assume that fast and automatic word recognition involves the use of a supraletter feature corresponding to the envelope or shape of the word when it is printed in lowercase. The advantages of mixed case over pure case and of pure lowercase over pure uppercase have often been taken as evidence favoring the word-shape hypothesis. Alternative explanations for these phenomena are offered. Experiment 1 shows that previous demonstrations of word-shape effects during proofreading are better described as individual letter effects. Experiments 2-4 explore the possibility that word shape facilitates lexical access through uncertainty reduction. In all three experiments performance on words with rare shapes is compared to those with common shapes. There were no effects of shape frequency in either tachistoscopic recognition or lexical-decision tasks. This was true regardless of the degree to which the visual shape cue was supplemented by the nonvisual factors of familiarity and expectancy. Possible reasons why fluent readers ignore word shape are discussed within the framework of a model that assumes that automatic word recognition is mediated by the activation of abstract letter identities.

Marcel (1978) has shown that semantic priming can occur in the lexical-decision task even if the prime is masked to the point at which its presence cannot be detected. The purpose of the present experiments was to determine if primes that begin four or five spaces to the right of fixation can also produce semantic facilitation even though they are very difficult to recognize. Experiment 1 showed that facilitation did occur when the parafoveal primes used in the subsequent experiments were presented foveally. In Experiment 2, the primes were moved to the parafovea, but the task demands directed the subject's attention toward the fovea. When subjects were ignoring the information presented to the parafovea (an allocation pattern that should correspond to that used during normal reading), neutral primes were just as effective as either semantically related or identical primes. In Experiment 3, the task demands were altered so that subjects were actively attending to the parafoveal primes. Although subjects were trying to process the primes, there was still no evidence that benefits could be derived from parafoveal primes. A final experiment showed that subjects given extensive practice with the materials will produce large amounts of identity and semantic priming. The results support the conclusion that readers can benefit little from the preprocessing of information in the parafovea unless that information can be supplemented with contextual expectations.Consider a reader who encounters the following sentence without any prior context: "For example, some words are much more predictable than others. " If the reader successively fixates to the positions indicated by the boldface type, it can be seen that information in the parafovea about the immediately upcoming word will sometimes be only minimally constrained by the previous context (e.g., the word "words"), but that other words (e.g., the word "others") will be highly predictable. The initial experiments of the present report concern the extent to which unanticipated words in the parafovea are processed and, equally important, whether or not any preprocessing of the parafoveal information actually speeds the reading process when an eye movement brings that part of the text into the fovea. We have tested these basic issues using a variation of the lexical-decision task to determine if a parafoveal prime can facilitate the processing of a related target Portions of these data were presented at the meeting of the Rocky Mountain Psychological Association, Tucson, April 1980. We would like to thank Susan Jones for collecting most of the data for Experiment 1 and for serving as one of our long-term subjects in Experiment 4. Earlier versions of this paper benefited from the comments of Keith Rayner and the CIP group at NMSU. We are especially indebted to Roger Schvaneveldt for the use of his equipment, computer programs, and general lore for doing lexical-decision experiments. Requests for reprints should be sent to Kenneth R. Paap, Department of Psychology, Box 3452,...

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The potential utility of dividing the information flowing from computer to human among several sensory modalitles is investigated by means of a rigorous experiment which compares the effectiveness of auditory and visual cues in the performance of a visual search task. The results indicate that a complex auditory cue can be used to replace cues traditionally presented in the visual modality. Implications for the design of multlmodal workstations are discussed.