Preparing words in speech production is normally a fast and accurate process. We generate them two or three per second in fluent conversation; and overtly naming a clear picture of an object can easily be initiated within 600 msec after picture onset. The underlying process, however, is exceedingly complex. The theory reviewed in this target article analyzes this process as staged and feedforward. After a first stage of conceptual preparation, word generation proceeds through lexical selection, morphological and phonological encoding, phonetic (...) encoding, and articulation itself. In addition, the speaker exerts some degree of output control, by monitoring of self-produced internal and overt speech. The core of the theory, ranging from lexical selection to the initiation of phonetic encoding, is captured in a computational model, called WEAVER++. Both the theory and the computational model have been developed in interaction with reaction time experiments, particularly in picture naming or related word production paradigms, with the aim of accounting for the real-time processing in normal word production. A comprehensive review of theory, model, and experiments is presented. The model can handle some of the main observations in the domain of speech errors (the major empirical domain for most other theories of lexical access), and the theory opens new ways of approaching the cerebral organization of speech production by way of high-temporal-resolution imaging. (shrink)

Levelt, reviewing the AGL field from a psycholinguistic perspective, identifies various gaps and makes a number of concrete suggestions for improving several currently used experimental designs. He raises the question whether artificial (and natural) grammar learning is about detecting ‘rules’, as is commonly assumed, or rather the detection of a set of ‘constraints’. He cautions the community to not ignore ‘semantics’, and recommends to consider less artificial tasks, that may be needed for learning more complex rules by human or (...) nonhuman animals. (shrink)

In his paper, MacKay reviews his Node Structure theory of error detection, but precedes it with a critical discussion of the Perceptual Loop theory of self-monitoring proposed in Levelt . The present commentary is concerned with this latter critique and shows that there are more than casual problems with MacKay's argumentation.

How can one conceive of the neuronal implementation of the processing model we proposed in our target article? In his commentary (Pulvermüller 1999, reprinted here in this issue), Pulvermüller makes various proposals concerning the underlying neural mechanisms and their potential localizations in the brain. These proposals demonstrate the compatibility of our processing model and current neuroscience. We add further evidence on details of localization based on a recent meta-analysis of neuroimaging studies of word production (Indefrey & Levelt 2000). We (...) also express some minor disagreements with respect to Pulvermüller's interpretation of the “lemma” notion, and concerning his neural modeling of phonological code retrieval. Branigan & Pickering discuss important aspects of syntactic encoding, which was not the topic of the target article. We discuss their well-taken proposal that multiple syntactic frames for a single verb lemma are represented as independent nodes, which can be shared with other verbs, such as accounting for syntactic priming in speech production. We also discuss how, in principle, the alternative multiple-frame-multiple-lemma account can be tested empirically. The available evidence does not seem to support that account. Footnotes1 BBS Note: The original manuscript of this Response article was received on January 14, 2000. (shrink)

The commentaries provide a multitude of perspectives on the theory of lexical access presented in our target article. We respond, on the one hand, to criticisms that concern the embeddings of our model in the larger theoretical frameworks of human performance and of a speaker's multiword sentence and discourse generation. These embeddings, we argue, are either already there or naturally forgeable. On the other hand, we reply to a host of theory-internal issues concerning the abstract properties of our feedforward spreading (...) activation model, which functions without the usual cascading, feedback, and inhibitory connections. These issues also concern the concrete stratification in terms of lexical concepts, syntactic lemmas, and morphophonology. Our response stresses the parsimony of our modeling in the light of its substantial empirical coverage. We elaborate its usefulness for neuroimaging and aphasiology and suggest further cross-linguistic extensions of the model. (shrink)

Lipkind et al. compare the development of vocal units and sound sequences in sound production in human infants and songbirds. Early in development, infant as well as songbird vocalizations vary along continuous acoustic parameters, with discrete vocal categories and structured vocalizations only emerging later on. This emergence process shows remarkable similarities between infants and zebra finches. Contrary to earlier views, Lipkind et al. suggest that the early development of songbird song (subsong) is more comparable to the phonation stage in infants (...) than to babbling. (shrink)

This commentary discusses whether abstract metrical frames are stored. For stress-assigning languages (e.g., Dutch and English), which have a dominant stress pattern, metrical frames are stored only for words that deviate from the default stress pattern. The majority of the words in these languages are produced without retrieving any independent syllabic or metrical frame.

It is a major move from the claim that the core linguistic problem in Broca's aphasia is the inability to deal with traces, to the claim that this is the syntactic operation only and that it is exclusively supported by Broca's region. Three arguments plead against this move. First, many Broca patients have no damage to Broca's area. Second, it is not only passive, but also active jabberwocky sentences that activate the frontal operculum in a judgment task. Third, the same (...) area is involved in a phrase-building production task that does not require tense processing. (shrink)

In modern approaches to phonology a lack of clarity exists on the issue of whether phonetic facts are psychological or physical realities. The results from an experiment suggest that phonetic facts can be considered as psychological realities, but with the restriction that they can take acoustical shape. More specifically, the syntactic material consisted of ambiguous French sentences of the following sort: On a tourné ce film intéressant pour les étudiants. They were spoken in disambiguating contexts, without the readers noticing the (...) ambiguities, and without context, but with the instruction to make a conscious effort to disambiguate. By tape splicing, the contexts were removed from the context-embedded sentences. Twenty-eight native speakers of French listened to the sentences and judged whether one or the other meaning had been intended by the speaker. Subjects performed significantly above chance: 60% correct identifications for context-embedded sentences, 75% for context-free sentences. Pitch-amplitude analyses were made to determine the acoustical differences involved. (shrink)

A comparison of Merge, a model of comprehension, and WEAVER, a model of production, raises five issues: merging models of comprehension and production necessarily creates feedback; neither model is a comprehensive account of word processing; the models are incomplete in different ways; the models differ in their handling of competition; as opposed to WEAVER, Merge is a model of metalinguistic behavior.

Artificial grammar learning (AGL) is used to study how human adults, infants, animals or machines learn various sorts of rules defined over sounds or visual items. Ten Cate et al. introduce the topic and provide a critical synthesis of this important interdisciplinary area of research. They identify the questions that remain open and the challenges that lie ahead, and argue that the limits of human, animal and machine learning abilities have yet to be found.

Levelt et al. describe a model of speech production in which lemma access is achieved via input from nondecompositional conceptual representations. They claim that existing decompositional theories are unable to account for lexical retrieval because of the so-called hyperonym problem. However, existing decompositional models have solved a formally equivalent problem.

Levelt, Roelofs, & Meyer (henceforth Levelt et al. 1999) propose a model of production incorporating a lemma stratum, which is concerned with the syntactic characteristics of lexical entries. We suggest that syntactic priming experiments provide evidence about how such syntactic information is represented, and that this evidence can be used to extend Levelt et al.'s model. Evidence from syntactic priming experiments also supports Levelt et al.'s conjecture that the lemma stratum is shared between the production and (...) comprehension systems. (shrink)

Levelt et al. attempt to “model their theory” with WEAVER ++. Modeling theories requires a model theory. The time is ripe for a methodology for building, testing, and evaluating computational models. We propose a tentative, five-step framework for tackling this problem, within which we discuss the potential strengths and weaknesses of Levelt et al.'s modeling approach.

Levelt, Roelofs & Meyer present a comprehensive and sophisticated theory of lexical access in production, but we question its reliance on binding-by-checking as opposed to binding-by-timing and we discuss how the timing of retrieval events is a major factor in both correct and errorful production.

The Popperian epistemology underlying Levelt's commentary and other aspects of contemporary psychology has limited application and, in particular, does not apply to the creation or development of theory, the main goal of MacKay . This is relevant to Levelt's questions, “What has changed?” and “What is the harvest?”: From a non-Popperian perspective, both changes and harvest are greater than Levelt's commentary would suggest and carry implications for the field at large.

Grice in pragmatics and Levelt in psycholinguistics have proposed models of human communication where the starting point of communicative action is an individual intention. This assumption, though, has to face serious objections with regard to the alleged existence of explicit representations of the communicative goals to be pursued. Here evidence is surveyed which shows that in fact speaking may ordinarily be a quite automatic activity prompted by contextual cues and driven by behavioural schemata abstracted away from social regularities. On (...) the one hand, this means that there could exist no intentions in the sense of explicit representations of communicative goals, following from deliberate reasoning and triggering the communicative action. On the other hand, however, there are reasons to allow for a weaker notion of intention than this, according to which communication is an intentional affair, after all. Communicative action is said to be intentional in this weaker sense to the extent that it is subject to a double mechanism of control, with respect both to present-directed and future-directed intentions. (shrink)

Any complete theory of lexical access in production must address how words are produced in prosodic contexts. Levelt, Roelofs & Meyer make some progress on this point: for example, they discuss resyllabification in multiword utterances. I present work demonstrating that word articulation takes into account overall prosodic context. This research supports Levelt et al.'s hypothesized separation between metrical and segmental information.

The theory of lexical selection presented by Levelt, Roelofs & Meyer addresses the mechanisms of semantic activation that lead to the selection of isolated words. The theory does not appear to extend naturally to the referential use of words in coherent discourse. A more complete theory of lexical selection has to consider the semantics of discourse as well as lexical semantics.

We discuss our concerns associated with three assumptions upon which the model of Levelt, Roelofs & Meyer is based: assumed generalisability of decontextualised experimental programs, assumed highly modular architecture of the language production systems, and assumed symbolic computations within the language production system. We suggest that these assumptions are problematic and require further justification.