Phonologically related lexical repetition disorder: a case study

Errors of repetition in aphasia are most often nonword substitutions. Phonologically related lexical errors, or formal errors, are real-word substitutions that overlap with target words in sound. In the present research we present the case of an aphasic patient, MMB, who produced an unusually high rate of formal paraphasias in repetition. Six experiments were conducted to investigate the combination of impairments contributing to MMB's pattern of repetition and to test the predictions made by two theories of formal errors. MMB's formal errors in repetition were influenced by target frequency, but not by target length or imageability. Formal errors tended to be more frequent than their targets and showed greatest phonological overlap with targets at initial consonant. These findings provided partial support for Martin and Saffran's fully interactive spreading activation account of formal errors and did not support Blanken's phonological interactive encoding account. In Experiment 6, the effect on repetition of increasing auditory verbal short-term memory (AVSTM) demands was examined using a paired word repetition experiment. Under these conditions, MMB produced semantic paraphasias for the first time, providing strong support for the Martin-Saffran hypothesis that phonologically related, and semantic, lexical repetition disorders lie on a continuum of severity moderated by the degree of AVSTM impairment.     

Text repetition and text integration

Two experiments explored the levels of text representation that mediate text repetition effects, following the Raney (2003) model. The magnitude of the repetition benefit in Experiment 1 supported predictions of Raney's model, indicating that the ease of forming a situation model contributed to the magnitude of the reprocessing benefit. In addition, representations organized around a good situation model were more sensitive to changes than were representations formed from reading without a good situation model. The results of Experiment 2 did not support the suggestion that the surface form and textbase are bound to a well-developed situation model, thereby limiting repetition effects to similar linguistic contexts. Rather, the nature of the repetition benefits in the present series of experiments are better explained by the degree o foverlap between passages at eachof the three levels of text representation.     

Word recognition during reading: The interaction between lexical repetition and frequency

Memory studies utilizing long-term repetition priming have generally demonstrated that priming is greater for low-frequency than for high-frequency words and that this effect persists if words intervene between the prime and the target. In contrast, word-recognition studies utilizing masked short-term repetition priming have typically shown that the magnitude of repetition priming does not differ as a function of word frequency and does not persist across intervening words. We conducted an eyetracking-while-reading experiment to determine which of these patterns more closely resembles the relationship between frequency and repetition during the natural reading of a text. Frequency was manipulated using proper names that were either high-frequency (e.g., Stephen) or low-frequency (e.g., Dominic). The critical name was later repeated in the sentence, or a new name was introduced. First-pass reading times and skipping rates on the critical name revealed robust repetition-by-frequency interactions, such that the magnitude of the repetition-priming effect was greater for low-frequency than for high-frequency names. In contrast, measures of later processing showed effects of repetition that did not depend on lexical frequency. These results are interpreted within a framework that conceptualizes eye-movement control as being influenced in different ways by lexical- and discourse-level factors.     

Components of activation: repetition and priming effects in lexical decision and recognition

Activation decay functions were examined in two different tasks: lexical decision and word recognition. Activation (amount of facilitation) was measured both for item repetition and for priming between newly learned associates. Results indicate that there are at least three different components of activation: a short-term component that decays with one or two intervening items and that appears to be common to priming and repetition; an intermediate component for repetition in recognition; and a long-term component for repetition.     

Nonword repetition in lexical decision: Support for two opposing processes

We tested and confirmed the hypothesis that the prior presentation of nonwords in lexical decision is the net result of two opposing processes: (1) a relatively fast inhibitory process based on global familiarity; and (2) a relatively slow facilitatory process based on the retrieval of specific episodic information. In three studies, we manipulated speed-stress to influence the balance between the two processes. Experiment 1 showed item-specific improvement for repeated nonwords in a standard “respond-when-ready” lexical decision task. Experiment 2 used a 400-ms deadline procedure and showed performance for nonwords to be unaffected by up to four prior presentations. In Experiment 3 we used a signal-to-respond procedure with variable time intervals and found negative repetition priming for repeated nonwords. These results can be accounted for by dual-process models of lexical decision (e.g., Balota & Chumbley, 1984; Balota & Spieler, 1999).     

Joint effects of semantic priming and repetition in a lexical decision task: Implications for a model of lexical access

An experiment is reported which showed that in a lexical decision task semantic priming by a related preceding word and repetition of target words produce additive effects on decision latency. Previous models of lexical access and modifications of them are discussed, and it is argued that some such models predict an interaction of priming and repetition, while others are insufficiently precise to make a prediction. It is suggested that the generality of effects across tasks requiring lexical access must be established and the components of complex effects must be separated before an adequate model can be devised to account for the data.     

Accessing lexical memory: The transfer of word repetition effects across task and modality

Reading by literate adults is generally assumed to represent skill acquired years earlier. However, the present experiments show that aspects of that skill can be readily modified. In two experiments, pronunciation of visually presented common words speeded later recognition of those words. This facilitation of recognition occurred although subjects did not expect word repetition and the task was changed from pronunciation to recognition. In contrast, naming pictures did not facilitate later recognition of visually presented picture names. The occurrence of facilitation when the task was changed and the lack of facilitation when stimulus format was changed suggest that facilitation occurs in the processes of encoding and accessing memory, processes that may change little across tasks but may change substantially with stimulus format changes. This facilitation of recognition occurs automatically without mediation by subjects’ expectations. A third experiment indicates that this facilitation of recognition shows little relation to episodic memory.     

The influence of global discourse on lexical ambiguity resolution

The influence of global discourse on the resolution of lexical ambiguity was examined in a series of naming experiments. Two-sentence passages were constructed to bias either the dominant or the subordinate meaning of a homonym that was embedded in a locally ambiguous sentence. The results provided evidence for the immediate (0-msec interstimulus interval) resolution of lexical ambiguity and were subsequently replicated in Experiment 2, in which an 80-msec stimulus onset asynchrony exposure duration was employed for the homonyms. Strong dominant and subordinate biased discourse contexts activated only the contextually appropriate sense of a homonym. In Experiment 3, each sentence of the discourse was presented in isolation. The pattern of activation obtained in Experiments 1 and 2 was found to be contingent on the integration of the two sentences to construct an overall global discourse representation of the text. The results support a context-sensitive model of lexical ambiguity resolution.     

Orthography and phonology in lexical decision: evidence from repetition effects at different lags

Full- and partial- (orthographic or phonemic) repetition effects for Hebrew voweled and unvoweled words and nonwords were examined at Lags 0 and 15 between the first and the second presentations. For voweled words, phonemic and orthographic partial-repetition effects were equivalent at Lag 0, each about half the size of the full-repetition effect. At Lag 15, the full-repetition effect was reduced to the size of phonemic repetition, which was as big as it was at Lag 0. In contrast, the orthographic repetition effect disappeared. For unvoweled words, the phonemic repetition effect was significant only at Lag 0, whereas the full-repetition effect was significant at both lags. Lexical decisions for both voweled and unvoweled nonwords were facilitated only by full repetition at Lag 0. It was concluded that addition of vowel marks attracted the subjects' attention and, therefore, lexical decisions for voweled stimuli were mediated by phonemic analysis.     

Sentential and discourse topic effects on lexical ambiguity processing: an eye movement examination

Models of lexical ambiguity resolution posit a role for context, but this construct has remained relatively undefined in the literature. The present study isolated two different forms of contextual constraint and examined how these sources of information might differentiate between a selective access and a reordered access model of ambiguity processing. Eye movements were monitored as participants read passages that contained either a balanced or a biased ambiguous word. The sentence containing the ambiguous word was held constant and instantiated either the subordinate meaning (Experiment 1) or the dominant meaning (Experiment 2) through the use of local context. These sentences were embedded in passages in which the topic was consistent, inconsistent, or neutral with respect to the meaning biased by the critical sentence. Experiment 1 provided evidence suggesting that the subordinate meaning of an ambiguous word was not selectively accessed even when sentence and discourse topic information biased that meaning. The data from Experiment 2 provided evidence that even the dominant meaning was not selectively accessed. These contextual sources of information were evaluated in terms of the roles they play in models of lexical ambiguity resolution.     

Perceptual and lexical components of auditory repetition priming in young and older adults

In the present study, we examined whether age modulates the processing of lexical and perceptual information in auditory implicit and explicit memory tests. Young and older adults performed a surface encoding task on spoken and printed words and then either identified degraded words or made explicit recognition judgments. The implicit test of perceptual identification yielded no evidence of age-related declines in the processing of either lexical information or coarse perceptual details (modality of presentation). The same test, however, produced marked age-related declines in the processing of fine-grained perceptual details (voice) when subjects were not familiarized with the talkers' voices prior to the encoding task. Marked age differences were also observed in recognition memory. These findings suggest that although aging preserves the encoding and incidental retrieval of lexical and coarse perceptual information, it affects the encoding of fine-grained perceptual information and deliberate retrieval processes.     

Word-specific repetition effects revealed by MEG and the implications for lexical access

This magnetoencephalography (MEG) study investigated the early stages of lexical access in reading, with the goal of establishing when initial contact with lexical information takes place. We identified two candidate evoked responses that could reflect this processing stage: the occipitotemporal N170/M170 and the frontocentral P2. Using a repetition priming paradigm in which long and variable lags were used to reduce the predictability of each repetition, we found that (i) repetition of words, but not pseudowords, evoked a differential bilateral frontal response in the 150–250 ms window, (ii) a differential repetition N400m effect was observed between words and pseudowords. We argue that this frontal response, an MEG correlate of the P2 identified in ERP studies, reflects early access to long-term memory representations, which we tentatively characterize as being modality-specific.     

Coreference and meaning

Sometimes two expressions in a discourse can be about the same thing in a way that makes that very fact evident to the participants. Consider, for example, ‘he’ and ‘John’ in ‘John went to the store and he bought some milk’. Let us call this ‘de jure’ coreference. Other times, coreference is ‘de facto’ as with ‘Mark Twain’ and ‘Samuel Clemens’ in a sincere use of ‘Mark Twain is not Samuel Clemens’. Here, agents can understand the speech without knowing that the names refer to the same person. After surveying many available linguistic and pragmatic tools (intentions to corefer, presuppositions, meanings, indexing, discourse referents, binding etc.) I conclude that we must posit a new semantic primitive to account for de jure coreference.     

A transfer analysis of the repetition effect in the lexical and ambiguity decision tasks

Two experiments were performed in an attempt to evaluate explanations of repetition priming-the facilitation observed when the same word is processed a second time in the same task. One task employed was lexical decision (word/nonword) and the other was ambiguity decision (ambiguous/ unambiguous). In the first experiment, transfer on a lexical decision task was measured following either a lexical decision or an ambiguity decision. When the identical lists were processed in the first phase for lexical and ambiguity decision, equal repetition effects were obtained on lexical decision. However, when the ambiguity task was presented without nonwords, no repetition priming occurred. In a second experiment, the within-task repetition effect was large for the ambiguity decision, whereas no transfer was obtained from lexical decision to ambiguity decision. The results were interpreted as being consistent with a transfer-appropriate processing account of repetition priming.     

Additive and interactive effects of word frequency and masked repetition in the lexical decision task

In previous studies, additive effects of masked repetition and word frequency on lexical decision latency have been reported. This additive pattern was replicated in Experiment 1 with the use of lowfrequency words (range, 1–7 per million) selected at random. In contrast, in Experiment 2, in which low-frequency words known to be familiar to the subjects were used, the masked repetition priming effect was greater for low-frequency than for high-frequency words. It is suggested that the absence of an interaction between masked repetition and frequency observed in previous studies and in the present Experiment 1 was due to the fact that very-low-frequency words often have an unstable representation in the subjects’ lexicon and, consequently, sometimes fail to produce repetition priming effects in full.     

Early integration of context during lexical access of homonym meanings

Evidence that lexical access is guided by context was obtained using a cross-modal, semantic priming paradigm. Subjects heard homonyms presented in context that favored only one meaning and made lexical decisions to contextually appropriate, inappropriate, or unrelated target words that were presented visually. In Experiment 1, responses were facilitated for only the contextually appropriate targets, at both 50 and 200 ms interstimulus intervals. In Experiment 2, the range of interstimulus intervals was increased and subjects were encouraged to consider multiple meanings of homonyms. Even with this orientation, lexical decisions were facilitated for only the contextually appropriate targets. This pattern of selective access was maintained across the full-time course of automatic activation, suggesting that the lexicon operates interactively rather than autonomously. These findings indicate that multiple, context-independent access of word meanings should not continue to be viewed as a mandatory operation of the language comprehension system. This research was conducted as part of a doctoral dissertation submitted to the University of California, Los Angeles. The Chair of the dissertation committee, Thomas D. Wickens, was especially helpful and supportive during every stage of this project. The assistance provided by committee members (Patricia Cheng, Victoria Fromkin, Eric Holman, Donald MacKay, and John Schumann) is also appreciated.     

Learning new vocabulary during childhood: Effects of semantic training on lexical consolidation and integration

Research suggests that word learning is an extended process, with offline consolidation crucial for the strengthening of new lexical representations and their integration with existing lexical knowledge (as measured by engagement in lexical competition). This supports a dual memory systems account, in which new information is initially sparsely encoded separately from existing knowledge and integrated with long-term memory over time. However, previous studies of this type exploited unnatural learning contexts, involving fictitious words in the absence of word meaning. In this study, 5- to 9-year-old children learned real science words (e.g., hippocampus) with or without semantic information. Children in both groups were slower to detect pauses in familiar competitor words (e.g., hippopotamus) relative to control words 24 h after training but not immediately, confirming that offline consolidation is required before new words are integrated with the lexicon and engage in lexical competition. Children recalled more new words 24 h after training than immediately (with similar improvements shown for the recall and recognition of new word meanings); however, children who were exposed to the meanings during training showed further improvements in recall after 1 week and outperformed children who were not exposed to meanings. These findings support the dual memory systems account of vocabulary acquisition and suggest that the association of a new phonological form with semantic information is critical for the development of stable lexical representations.     

Nonword repetition priming in lexical decision reverses as a function of study task and speed stress

The authors argue that nonword repetition priming in lexical decision is the net result of 2 opposing processes. First, repeating nonwords in the lexical decision task results in the storage of a memory trace containing the interpretation that the letter string is a nonword; retrieval of this trace leads to an increase in performance for repeated nonwords. Second, nonword repetition results in increased familiarity, making the nonword more "wordlike," leading to a decrease in performance. Consistent with this dual-process account, Experiment 1 showed a facilitatory effect for nonwords studied in a lexical decision task but an inhibitory effect for nonwords studied in a letter-height task. Experiment 2 showed inhibitory nonword repetition priming for participants tested under speed-stress instructions.