Prior to each visually presented target letter string in a speeded word-nonword classification task, either BIRD, BODY, BUILDING, or xxx appeared as a priming event. When the target was a word, it was (a) a name of a type of bird on most BiRD-prime trials; (b) a name of part of a building on most BODY-prime trials; (c) a name of a part of the body on most BUiLDiNG-prime trials; (d) a name of a type of bird, part of a building, or part of the body equally often on xxx-prime trials. Thus, on BiRD-prime trials the subject expected the word target to be chosen from the same category as the category represented by the word prime itself (Nonshift), whereas on BODY-prime and BuiLDiNG-prime trials the subject's attention was to be shifted because he or she expected the word target to be chosen from a category other than the category represented by the word prime itself (Shift). The word target was an exemplar of either the category the subject expected (Expected) or a category the subject did not expect (Unexpected) and was either semantically related (Related) or semantically unrelated (Unrelated) to the word prime. Thus, there were five different types of word-prime-word-target trials: (a) BiRD-robin (Condition Nonshift-Expected-Related) ; (b) BiRD-arm (Condition Nonshift-Unexpected-Unrelated) ; (c) BODY-door (Condition Shift-Expected-Unrelated) ; (d) BODY-sparrow (Condition Shift-Unexpected-Unrelated); (e) BODYheart (Condition Shift-Unexpected-Related). The stimulus onset asynchrony (SOA) between the prime and the target letter string varied between 250 and 2,000 msec. At the 2,000-msec SOA, reaction times (RTs) on BiRD-robin type trials were faster than RTs on xxx-prime trials (a facilitation effect), whereas RTs on BIRDarm type trials were slower than RTs on xxx-prime trials (an inhibition effect). As SOA decreased, the facilitation effect on BiRD-robin trials remained constant, but the inhibition effect on BiRu-arm trials decreased until, at the 250-msec SOA, there was no inhibition. For the Shift conditions at the 2,000-msec SOA, facilitation was obtained on BODY-door type trials and inhibition was obtained on BODY-sparrow type trials. These two effects decreased in magnitude as the SOA decreased until, at the 250-msec SOA, there was no facilitation or inhibition. On BODY-heart type trials, there was an inhibition effect at the 2,000 msec SOA, which decreased as the SOA decreased until, at the 250-msec SOA, it became a facilitation effect. For the nonword targets, the facilitatory effects of the word primes decreased as SOA decreased. These results were regarded as supporting the theory of Posner and Snyder that postulates two distinct components of attention: a fast automatic inhibitionless spreading-activation process and a slow limited-capacity consciousattention mechanism.

One could easily argue that the most commonly studied stimulus set in experimental psychology involves English words. The study of the memory and reading of words has been central to research since Cattell (1886). Words are well-described units that provide the link between perception and meaning, and so have been critical to developments in computational modeling (e.g., McClelland & Rumelhart, 1981), neuroimaging (e.g., Petersen, Fox, Posner, Mintun, & Raichle, 1989, and conceptions of attention and automaticity (e.g., Neely, 1977;Stroop, 1935), among many other research areas.Given the importance of words as a stimulus set, one might assume that there are relatively straightforward ways to study lexical processing, and that there is a wellconstrained set of findings to which one can appeal in building models of word processing. Although there has been considerable progress in understanding how people process words, there are some clear gaps in the available literature. This paper describes the English Lexicon Project (ELP), which provides a behavioral database for over 40,000 words and nonwords that will help fill some of these gaps. The present description will focus on visual word recognition, although, as described below, the current database has relevance for other aspects of word processing, such as memory and speech production. Before describing the ELP, we will briefly describe the behavioral measures in the database, the limitations in our current knowledge, and how this database will help address these limitations. LEXICAL DECISIONS AND NAMING AS THE BEHAVIORAL TARGETSAlthough there are multiple ways to measure lexical processing (e.g., eye-fixation data, probability of iden- The English Lexicon Project is a multiuniversity effort to provide a standardized behavioral and descriptive data set for 40,481 words and 40,481 nonwords. It is available via the Internet at elexicon.wustl.edu. Data from 816 participants across six universities were collected in a lexical decision task (approximately 3400 responses per participant), and data from 444 participants were collected in a speeded naming task (approximately 2500 responses per participant). The present paper describes the motivation for this project, the methods used to collect the data, and the search engine that affords access to the behavioral measures and descriptive lexical statistics for these stimuli.

Immediately prior to each visually presented target letter string to which the subject made a speeded word-nonword classification response, a visually presented prime to which no overt response was required was shown for 360, 600, or 2,000 msee. For word (W) target trials, the priming event was either a semantically neutral warning signal (Condition NX), a word semantically related to the target word (Condition R), or a word semantically unrelated to the target word (Condition U); for nonword (N) target trials, the priming event was either the neutral warning signal (Condition NX) or a word prime (Condition WP). For the W target trials, reaction times (RTs) were slower in Condition U than in Condition NX and equally so for all three prime durations; RTs were faster in Condition R than in Condition NX and to a greater degree for the 600-and 2,OOO-msec prime durations than for the 360-msec prime duration. For the N targets, RTs were faster in Condition WP than in Condition NX and equally so for all prime durations. These results were interpreted within the framework of a two-factor theory of attention proposed by Posner and Snyder (1975a).In the lexical decision task, a subject must decide as quickly as possible whether a visually presented letter string is a common English word or nonword. A commonly obtained finding (e.g., Meyer & Schvaneveldt, 1971; Meyer, Schvaneveldt, & Ruddy, Note 1) is that subjects are quicker to respond that a target letter string (e.g., NURSE) is a word when the immediately prior target was a semantically related word (i.e., DOCTOR) than when the immediately prior target was a semantically unrelated word (e.g., BREAD). Schvaneveldt and Meyer (1973) have proposed two models, each of which can account for this semantic-facilitation effect. Both models share the assumption that, in terms of a spatial metaphor, the logogens for semantically related words are located nearer each other in semantic memory than are the logogens for semantically unrelated words (cf. Morton, 1970). According to the spreading excitation model, when a stimulus word activates its logogen, this activation spreads to adjacent, semantically related logogens but not to remote, semantically unrelated logogens. Thus, if a word that is to be processed is presented before there has been a complete decay of the logogen activation produced by a previously presented semantically related word, the activation level in the logogen of the to-be-processed word will initially be higher (due to the activation that has spread to it) than it would This research was supported by Grant 4031 OX to Dr. Michael 1. Posner from the National Science Foundation and was conducted while Dr. Posner was a Visiting Professor at Yale and while the author was a National Science Foundation predoctoral fellow. 1 am indebted to Dr. Robert G. Crowder, Dr. Alice F. Healy, and Dr. Posner for several interesting discussions about this research. Requests for reprints should be sent to the author, who is now at the Department of Psychology, University of Sout...

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