Lexicalisation in Speech Production: Evidence From Form Related Word Substitutions in Aphasia

Abstract

One of the major empirical sources of theories of speech production are speech errors in normal speakers. Speech errors occurring during lexicalisation of a concept to be expressed can result in whole-word substitutions that are target related in form and/ or meaning or can appear as nonword productions (neologism). Similar error phenomena have been reported for aphasic patients. The present study describes the aphasic, HZ, who produced mainly form-related word substitutions and neologisms in several single-word processing tasks (picture naming, repetition, and reading aloud). In picture naming, meaning-related substitutions also occurred as well as substitutions that were related both in meaning and form (mixed errors). Three hypotheses of the origin of formal errors were tested: the full interactive activation hypothesis postulating meaning-form interactions, the lexical (form) retrieval hypothesis, and the post-lexical phonological encoding hypothesis. HZ's performance on repetition and reading aloud (tests showed no mixed errors and no effects of imageability and of target frequency on formal errors) failed to support the predictions of the first two hypotheses. However, the phonological encoding hypotheses (enriched by a comprehensionbased editor) could also not account for the data (e.g. for some task-specific asymmetries in the error pattern). Instead, an attempt is made to account for formal and mixed errors by construing word form encoding as an interactively organised component within a two-stage model of lexicalisation. Formal errors are traced back to interactions between lexical forms and sublexical phonological information during the second stage of lexicalisation. Mixed errors occur when lexical forms of the target's semantic competitors are involved in word form encoding.

Phonologically Related Lexical Repetition Disorder: A Case Study

“…Frequency values of formal paraphasias were obtained from Kucera and Francis (1967). Only errors with a frequency difference of more than five were scored as unequal (Blanken, 1998).…”

“…Formal errors (here and throughout the present research) were classified according to Blanken's (1998) criteria of two or more shared phonemes with the target (e.g., Pudding → Plastic) or one shared phoneme also sharing segmental position (e.g., Truck → Table).…”

“…A different account of formal errors is proposed by Blanken (1998), who suggests they can be traced back to impairment of the speech production system itself, causing errors in phonological encoding for production. Blanken's theory assumes that formal errors retain their lexical status because the process of phonological encoding is itself bidirectionally interactive in the sense that, during preparation for output, phonetic (segmental/metric) units send activation back to lexical units.…”

“…Thus, Butterworth (1979) referred to whole-word substitutions sharing phonological overlap with the target as ''jargon homophones.'' However, this view necessarily predicts small numbers of formal paraphasias in any one patient's error corpora, and several authors have since presented cases in which ratios of formal errors far exceeded what could be predicted from estimates of chance occurrences (Best, 1996;Blanken, 1990Blanken, , 1998Martin & Saffran, 1992).The majority of research conducted on real-word errors in aphasia has focused on semantic paraphasias (Howard & Franklin, 1988;Katz & Goodglass, 1990;Martin & Saffran, 1992;Michel & Andreewsky, 1983). The tendency toward a high proportion of semantically related word substitutions (arm → leg; happy → content) forms part of the symptom complex called ''deep dysphasia,'' a disorder in repetition that is parallel to the disorder of deep dyslexia in reading.…”

“…Patients with deep dysphasia tend to produce formal paraphasias in addition to semantic word substitutions, although the proportion of one error type to another varies across individual cases (Howard & Franklin, 1988;Katz & Goodglass, 1990;Martin & Saffran, 1992;Michel & Andreewsky, 1983;Morton, 1980). Recently, two theories have been proposed to account for formal errors in naming and repetition (Blanken, 1998;Martin & Saffran, 1992), based on principles from Dell's (1986) interactive spreading activation language model. Dell's model was developed as a theory of language production, but has since been extended to input processes (Martin & Saffran, 1992;Martin, Saffran, & Dell, 1996).…”