Subjects were shown the terms of simple sentences in sequence (e.g., “A sparrow / is not / a vehicle”) and manually indicated whether the sentence was true or false. When the sentence form was affirmative (i.e., “X is a Y”), false sentences produced scalp potentials that were significantly more negative than those for true sentences, in the region of about 250 to 450 msec following presentation of the sentence object. In contrast, when the sentence form was negative (i.e., “X is not a Y”), it was the true statements that were associated with the ERP negativity. Since both the false‐affirmative and the true‐negative sentences consist of “mismatched” subject and object terms (e.g., sparrow / vehicle), it was concluded that the negativity in the potentials reflected a semantic mismatch between terms at a preliminary stage of sentence comprehension, rather than the falseness of the sentence taken as a whole. Similarities between the present effects of semantic mismatches and the N400 associated with incongruous sentences (Kutas & Hillyard, 1980) are discussed. The pattern of response latencies and of ERPs taken together supported a model of sentence comprehension in which negatives are dealt with only after the proposition to be negated is understood.

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Completion responses were collected for two sets of sentence contexts, which were designed to produce different distributions of probabilities for the primary responses. The subje~t population consisted of undergraduate college students. For each context, responses and their respective probability of occurrence are listed, and an index of the primary responses is provided. It is hoped that these normative materials will facilitate comparison among future studies of the effects of sentence contexts on word processing.Meaning is conveyed in language through sequences of words. The study of the relationship between comprehension of meaning and the processing of individual words has taken several forms in contemporary psychological research. A common method involves presenting literate subjects with contexts in the form of incomplete sentences. In educational research, Taylor's (1953) "doze" method has been widely used: Readers are presented prose passages of one or more sentences from which a number of words have been omitted. The reader's task is to fill in the word or words that seem the most appropriate completions of the context. Generally, as the context becomes more informative, in the sense of reducing uncertainty about possible alternative completions (Shannon, 1948), the range of responses elicited from a sample of readers becomes smaller, and anyone reader's ability to predict the most probable response increases. This simple procedure has been used to derive measures of text readability (e.g., Bormuth, 1975), assess the amount of information gained from reading a passage (e.g., Coleman & Miller, 1968;Rubenstein & Aborn, 1958), and assess the ability of readers of a certain grade level (e.g., Rankin & Overholzer, 1969) or reading level (e.g., Neville & Pugh, 1976-1977 to make use of contextual cues in reading.In psychology, use of doze-like procedures naturally followed the acceptance within psychology of the concepts of information theory. Miller and Selfridge (1950) had subjects generate sentence-like "approximations to English" in which the words in a sequence were constrained by a variable number of preceding words (n). As the level of constraint increased, acquisition and retention of the passages improved regularly up to about n = 7. Similarly, Aborn, Rubenstein, and Sterling (1959) showed that most of the information used in generating doze completions typically came from within seven or eight words preceding the missing word.Several studies of word recognition demonstratedWe would like to thank Karen Bryant for her assistance in data collection. Requests for reprints should be addressed to

Subjects were shown pairs of letter strings and had to decide as quickly as possible whether both strings were words. The word pairs included associates (e.g., cat-dog), words not normatively associated that had been rated by other subjects as semantically similar (e.g., nurse-wife), and unrelated control pairs (e.g.. bread-stem). Both associates and semantically related pairs were responded to more quickly than were the corresponding control pairs. The magnitude of the facilitation for the associates appeared to be related more to the semantic similarity ratings than to measures of either direct or indirect associative strength. It was concluded that the encoding of a word can be facilitated by the prior processing of a semantically related word.In a lexical decision task, the subject is asked to decide whether or not a given stimulus is a word, Meyer and Schvaneveldt (1971) have shown that latency to decide that two presented items were both words was shorter if the second word was a primary associate of the first, as with the pair "bread-butter." For a number of reasons, this association effect has been influential in recent elaborations of semantic memory theory. First, the task is at least nominally a lexical rather than a semantic one, and the subject is not

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