According to certain theories of language production, lexical access to a content word consists of two independent and serially ordered stages. In the fust, semantically driven stage, so-called lemmas are retrieved, i.e., lexical items that are specified with respect to syntactic and semantic properties, but not with respect to phonological characteristics. In the second stage, the corresponding wordforms, the so-called lexemes, are retrieved. This implies that the access to a content word involves an early stage of exclusively semantic activation and a later stage of exclusively phonological activation. This seriality assumption was tested experimentally, using a picture-word interference paradigm in which the interfering words were presented auditorily. The results show an interference effect of semantically related words on picture naming latencies at an early SOA (-150 ms), and a facilitatory effect of phonologically related words at later SOAs (0 ms, + 150 ms). On the basis of these results it can be concluded that there is indeed a stage of lexical access to a content word where only its meaning is activated, followed by a stage where only its form is activated. These findings can be seen as empirical support for a two-stage mode1 of lexical access, or, alternatively, as putting constraints on the parameters in a network mode1 of lexical access, such as the model proposed by Dell and Reich. o 1990 Academic PKSS, IIIC.One of the most influential models of language production has been proposed by Garrett (e.g., 1976Garrett (e.g., , 1980Garrett (e.g., , 1988. According to this model, the formulation of a sentence involves a sequence of processes generating different levels of representation.On the basis of a preverbal representation of what the speaker wants to express the functional level representation is generated. It encodes the meanings of the lexical items and the grammatical relationships between them. Based on the functional level representation, the positional level representation is constructed, which encodes the phonological forms of the words and their order in the surface structure of the sentence.We thank Ger Dessejer and Hans Franssen, who ran the experiments with admirable patience and competence, Kay Bock, Gary Dell, and two anonymous reviewers for helpful comments on an earlier version of the manuscript. Send requests for reprints to Herbert Schriefers, Max-Planck-Institute for Psycholinguistics,

Lexical access in object naming involves the activation of a set oflexical candidates, the selection of the appropriate (or target) item, and the phonological encoding of that item. Two views of lexical access in naming are compared. From one view, the 2-stage theory, phonological activation follows selection of the target item and is restricted to that item. From the other view, which is most explicit in activation-spreading theories, all activated lexical candidates are phonologically activated to some extent. A series of experiments is reported in which subjects performed acoustic lexical decision during object naming at different stimulus-onset asynchronies. The experiments show semantic activation of lexical candidates and phonological activation of the target item, but no phonological activation of other semantically activated items. This supports the 2-stage view. Moreover, a mathematical model embodying the 2-stage view is fully compatible with the lexical decision data obtained at different stimulus-onset asynchronies.One of a speaker's core skills is to lexicalize the concepts intended for expression. Lexicalization proceeds at a rate of two to three words per second in normal spontaneous speech, but doubling this rate is possible and not exceptional. The skill of lexicalizing a content word involves two components. The first one is to select the appropriate lexical item from among some tens of thousands of alternatives in the mental lexicon. The second one is to phonologically encode the selected item, that is, to retrieve its sound form, to create a phonological representation for the item in its context, and to prepare its articulatory program. An extensive review of the literature on lexicalization can be found in Levelt (1989). This article addresses only one aspect of lexicalization, namely its time course. In particular, we examine whether the selection of an item and its phonological encoding can be considered to occur in two successive, nonoverlapping stages.We acknowledge the invaluable contributions of John Nagengast and Johan Weustink, who programmed the computer-based experiments; ofGer Desserjer and Hans Fransen, who ran the experiments and assisted in data analysis; and of lnge Tarim, who provided graphical assistance. We also acknowledge Gary Dell's and Picnic Zwitserlood's detailed comments on an earlier version of this article, as well as the thorough comments of an anonymous reviewer.

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Subjects named pictures while hearing distractor words that shared word-initial or word-final segments with the picture names or were unrelated to the picture names. The relative timing of distractor and picture presentation was varied. Compared with unrelated distractors, both types of related distractors facilitated picture naming under certain timing conditions. Begin-related distractors facilitated the naming responses if the shared segments began 150 ms before, at, or 150 ms after picture onset. By contrast, end-related distractors only facilitated the responses if the shared segments began at or 150 ms after picture onset. The results suggest that the phonological encoding of the beginning of a word is initiated before the encoding of its end.