An interactive 2-step theory of lexical retrieval was applied to the picture-naming error patterns of aphasic and nonaphasic speakers. The theory uses spreading activation in a lexical network to accomplish the mapping between the conceptual representation of an object and the phonological form of the word naming the object. A model developed from the theory was parameterized to fit normal error patterns. It was then "lesioned " by globally altering its connection weight, decay rates, or both to provide fits to the error patterns of 21 fluent aphasic patients. These fits were then used to derive predictions about the influence of syntactic categories on patient errors, the effect of phonology on semantic errors, error patterns after recovery, and patient performance on a single-word repetition task. The predictions were confirmed. It is argued that simple quantitative alterations to a normal processing model can explain much of the variety among patient patterns in naming. Difficulty in word retrieval is the most pervasive symptom of language breakdown in aphasia. As with other symptoms of brain damage, word retrieval is subject to graceful degradation (Marr, 1982; Rumelhart & McClelland, 1986): Unsuccessful attempts at retrieval generally resemble the target, either in

A computational model of human memory for serial order is described (OSCillator-based Associative Recall [OSCAR]). In the model, successive list items become associated to successive states of a dynamic learning-context signal. Retrieval involves reinstatement of the learning context, successive states of which cue successive recalls. The model provides an integrated account of both item memory and order memory and allows the hierarchical representation of temporal order information. The model accounts for a wide range of serial order memory data, including differential item and order memory, transposition gradients, item similarity effects, the effects of item lag and separation in judgments of relative and absolute recency, probed serial recall data, distinctiveness effects, grouping effects at various temporal resolutions, longer term memory for serial order, list length effects, and the effects of vocabulary size on serial recall. The serial ordering of behavior is central to much, perhaps most, of human cognition (e.g., Lashley, 1951). Studies of memory for serial order have provided rich data on the psychological repre-sentation of serial order information and therefore offer a signifi-cant challenge to any model of serially ordered behavior. In this

In 1951, Lashley highlighted the importance of serial order for the brain and behavioural sciences. He considered the response chaining account untenable and proposed an alternative employing parallel response activation and "schemata for action". Subsequently, much has been learned about sequential behaviour, particularly in the linguistic domain. We argue that these developments support Lashley's picture, and recent computational models compatible with it are described. The models are developed in a series of steps, beginning with the basic problem of parallel response competition and its possible resolution into serial action. At each stage, important limitations of the previous models are identified and simple additions proposed to overcome them, including the provision of learning mechanisms. Each type of model is compared with relevant data, and the importance of error data is emphasized. Taken together, the models constitute a unified approach to serial order which has achieved considerable explanatory success across disparate domains.

After reviewing situational and demographic factors that have been argued to affect speakers' disfluency rates, we examined disfluency rates in a corpus of task-oriented conversations(Schober & Carstensen, 2001) with variables that might affect fluency rates. These factors included: speakers' ages (young, middle-aged, and older), task roles(directorvs. matcher in a referentialcommunication task), difficulty of topic domain (abstract geometric figures vs. photographsof children),relationshipsbetween speakers(marriedvs. strangers), andgender(each pair consistedof a man anda woman).Older speakersproduced only slightly higher disfluency rates than young and middle-aged speakers. Overall, disfluency rates were higher both when speakers acted as directors and when they discussed abstract figures, confirming that disfluencies are associatedwith an increasein planningdifficulty. However, fillers(such as uh)were distributedsomewhat differentlythan repeatsor restarts, supportingthe idea that fillers may be a resourcefor or a consequence of interpersonal coordination.

co-occurrence restrictions Ethiopian Semitic similarity speech errors This article reports the results of speech error elicitation experiments investigating the role of two consonant co-occurrence restrictions in the productive grammar of speakers of two Ethiopian Semitic languages, Amharic and Chaha. Higher error rates were found with consonant combinations that violated co-occurrence constraints than with those that had only a high degree of shared phonological similarity or low frequency of co-occurrence. Sequences that violated two constraints had the highest error rates. The results indicate that violations of consonant co-occurrence restrictions significantly increase error rates in the productions of native speakers, thereby supporting the psychological reality of the constraints. 1

People produce long sequences such as speech and music with incremental planning: mental preparation of a subset of sequence events. The authors model in music performance the sequence events that can be retrieved and prepared during production. Events are encoded in terms of their serial order and timing relative to other events in a planning increment, a contextually determined distribution of event activations. Planning is facilitated by events ’ metrical similarity and serial/temporal proximity and by developmental changes in short-term memory. The model’s predictions of larger planning increments as production rate decreases and as producers ’ age–experience increases are confirmed in serial-ordering errors produced by adults and children. Incremental planning is considered as a general retrieval constraint in serially ordered behaviors. When people produce long, complex sequences such as speech and music, they must plan what event to produce next (the serialorder problem) and when to produce it (the timing problem). Bernstein (1967) and Lashley (1951) both pointed to music as a quintessential example of serial-ordering abilities because of its complexity, length, and temporal properties. Although musical

Speech errors reflect linguistic knowledge. For example, phonological errors follow languagewide phonotactic constraints such as the fact that [h] must be an onset in English. We review five experimental studies that demonstrate that errors adhere to artificial experiment-wide constraints (e.g. [f] must be an onset during this experiment) as well as language-wide constraints. These studies show that the language production system adapts to its recent experience with phonological patterns. 1

This paper confirms and exploits the observation that early overt self-interruptions and repairs of phonological speech errors very likely are reactions to inner speech, not to overt speech. In an experiment eliciting word–word and nonword–nonword phonological spoonerisms it is found that self-interruptions and repairs come in two classes, one class of reactions to inner speech, another with reactions to overt speech. It is also found that in inner speech nonword–nonword spoonerisms are more often rejected than word–word spoonerisms. This is mirrored in the set of completed spoonerisms where word–word spoonerisms are more frequent than nonword–nonword ones. This finding supports a classical but controversial explanation of the well-known lexical bias effect from nonwords being rejected more frequently than real words in inner speech. This explanation is further supported by an increasing number of overt rejections of nonword–nonword spoonerisms with phonetic distance between error and target, and increasing lexical bias with phonetic distance. It is concluded that the most likely cause of lexical bias in phonological speech errors is that nonword errors are more often detected, rejected, and repaired than real-word errors in self-monitoring of inner speech.

This study asked whether new linguistic patterns acquired through recent perception experience can transfer to speech production. Participants heard and spoke sequences of syllables featuring novel phonotactic constraints (e.g. /f / is always a syllable onset, /s / is always a syllable coda). Participants ’ speech errors reflected weaker learning of the constraints present in the spoken sequences (e.g. /f / must be onset) when they heard sequences with the inverse constraints (e.g. /f / must be coda), suggesting that the constraints experienced in perception interfered with learning in production. The results did not depend on the presence of a shared orthographic code in perception and production trials, suggesting that direct transfer between heard speech and produced speech is possible, perhaps through prediction via inner speech. Further work is needed to determine the exact mechanism supporting inter-modality transfer of phonological generalizations.

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