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Verbal working memory and speech errors

Verbal working memory and speech errors. Eleanor Drake 15 th February 2008. Outline. Introduction Working memory Phonological loop Measuring function Short-term memory and speech errors Saito and Baddeley (2004) exp. 1 Current study Aim Speech task Results and interpretation

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Verbal working memory and speech errors

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  1. Verbal working memory and speech errors Eleanor Drake 15th February 2008

  2. Outline • Introduction • Working memory • Phonological loop • Measuring function • Short-term memory and speech errors • Saito and Baddeley (2004) exp. 1 • Current study • Aim • Speech task • Results and interpretation • Correlatory findings • Results and interpretation

  3. Introduction • Saito and Baddeley (2004) report correlation between vSTM performance and speech error rate. • Current study aim = determine if correlation replicable using different error-elicitation paradigm.

  4. Working Memory • Responsible for temporary storage and processing of information. • Baddeley and Hitch (1974) model has been highly influential. • Proposed a system involving a central executive + subservient modality specific visuo-spatial sketch pad and phonological loop (and an episodic buffer, in later versions). • Phonolgical loop function focus of current study.

  5. Working memory model

  6. Phonological loop • Responsible for short-term storage, and checking of verbal material • Bi-componential: • Phonological store: • storage of phonologically encoded information • information subject to decay (c. 1.5-2s) • Subvocal articulatory rehearsal • Cycles phonologically encoded information to refresh store • Recoding non-phonological (i.e., printed word) into phonological form • Evidence- “word-length effect”, “articulatory suppression”

  7. Measures of phonological loop function • Forward serial recall • (e.g., Wechsler 2003 digit span) • Taken to relate to rate of articulatory rehearsal (i.e., individuals with a higher score rehearse more rapidly) • Repetition or matching • Measures verbal short-term memory

  8. Measures of phonological loop function • Nonword repetition • Repetition of phonotactically acceptable but lexically empty syllable strings • Minimize contribution of long-term phonological, lexical, and semantic knowledge (Gathercole & Baddeley, 2003) • Greater reliance on auditory discrimination, motor planning and execution (Edwards and Lahey, 1998) • Measures phonological short-term memory

  9. STM and speech production errors • Why might there be a correlation? • Qualitatively similar errors = common locus in information processing? • E.g., Ellis, 1980; Page et al, 2007 • Similarity can be simulated via computational modelling (Page and Norris, 1998a) • “Serial-ordering mechanism” malfunction as origin of normal speech errors • E.g, Nespoulos et al. 1984 • vSTM lower in PWS • (Bosshardt 1990; Bosshardt 1993)

  10. Saito and Baddeley (2004) • Experiment 1 • Does elicited speech error rate relate to phonological loop function? • Measured PL function via serial digit recall • Auditory distractor technique as error-elicitation paradigm • Target word (e.g., “shizuoka”) produced in response to tone. • Cue tone replaced 1/10 by similar distractor word (e.g., “shiozuke”), 1/10 by dissimilar distractor

  11. Saito and Baddeley (2004)

  12. Saito and Baddeley (2004) • Findings • Error rate = .031/ .291 (dissimilar/ similar condition) • Speech error rate correlated with digit span task performance; r = - 0.33, p < .05. • Interpretation • Both vSTM and speech task performance share predication on a “phonological planning factor”

  13. Current study • Does the correlation hold for: • another error-elicitation paradigm? • Uses Wilshire’s (1999) tongue-twister task • different tests of auditory short-term memory? • Uses serial digit recall, serial digit matching, and NWR

  14. Speech errors • Task involves reading monosyllabic words • Errors (i.e., deviations from the speech plan) assumed to occur at level of • Formulation • Phonological encoding • Articulation • Execution fault in control of muscular processes • Not conceptualisation

  15. Speech error elicitation • Wilshire (1999) • 64 “tongue-twisters” • 4 monosyllabic words on screen, sequence to be repeated 4 times, at rate of 100 wpm • 32 control, 16 ABBA onset, 16 ABAB onset • Of 32 non-control items 16 alliterating similar, 16 alliterating dissimilar (near even distribution) • Egs.-

  16. Quadruple examples • Control- CUB TIME DATE SIN • ABBA dissimilar - BED COUGH CARD BEEF • ABBA similar - DIRT BUS BOOT DOSE • ABAB dissimilar - TIN MAP TYPE MOON • ABAB similar - SAP TIFF SURF TOP

  17. Other parameters • Serial digit recall repetition • Serial digit recall matching • Nonword repetition • Digit articulation time • N =15

  18. Tongue-twister results • Error-rate:- 16.7% quadruples errorful • Error-rate by individual words within quad:- • Overall = 1.5% • Control = .71% • ABBA dissimilar = .63% • ABAB dissimilar = 1.77% • ABBA similar = 1.77% • ABAB similar = 4.13%

  19. Tongue-twister results • Analysis of variance • A/S significantly more error prone than • Control (t = 3.66, p < .005) • A/D (t = 3.51, p < .005) • (control v A/D; no significant difference) • ABAB significantly more error prone than • Control (t = 4.138, p < .005) • ABBA (t = 3.032, p < .05) • (control v ABBA; no significant difference)

  20. Percentage of syllables produced incorrectly by quad type and position within quad percentage of syllables produced incorrectly 10 9 8 7 6 words1 Word 2 5 Word 3 Word 4 4 3 2 1 0 control ABBA dissimilar ABAB dissimilar ABBA similar ABAB similar Quad type Tongue-twister results • Word position: • Word 3 (e.g., sap tiff surf top) significantly more error prone (for ABAB sub-set)

  21. Tongue-twister results • Reiteration • 1st recitation less error prone • 2 v 1: t = 2.68 • 3 v 1: t = 2.48 p < .05 all cases • 4 v 1: t = 2.63 • No significant differences amongst other recitation numbers.

  22. Tongue-twister results • Summary • Error rate higher when • ABAB … and/ or • A/S • Word position 3 • Error rate significantly lower • 1st recitation

  23. Discussion speech task • Speech error rate (1.5%) • Wilshire (4.5%) • Heterogeneity of participants, experimental conditions, error-sensitivity of scorer • Saito and Baddeley (29.6%) • In error-eliciting conditions • Spontaneous speech (0.1-0.2%) (Garnham et al. 1981) • Suggests paradigm does elicit errors

  24. Discussion speech task • A/S > A/D:- phonological similarity effect • Conforms with Wilshire (1999) • Cf. PSE in serial recall • ABAB > ABBA:- • Contrary to Wilshire (1999) • Contrary to Sevald and Dell (1994) • Design flaw? • Requires control experiment

  25. Discussion speech task • Word 1 > words 2/ 3/ 4 • In ABAB subset • Point at which A and B onsets are equiprobable • Experimental design -> preference for ABBA?

  26. Discussion speech tasks • Recitation 1 < recitation 2/ 3/ 4 • Consistent with Wilshire (1999) • She proposes explanations • Phonological planning fatigue? • Strategies by which plan re-used? • Interference/ decay (cf. WM model) • Another suggestion • Overt articulation having occurred impacts on psychological/ physiological representations of the phrase

  27. Discussion speech tasks • How? • Feedback from production creating interefernce • Overt articulation (opposed to articulatory rehearsal) -> • Proprioceptive or sensorimotor feedback • Auditory feedback

  28. Discussion speech tasks • Proprioceptive/ sensorimotor • Suggested in stuttering literature (e.g., Max et al. 2004) • A/S more error-prone because of gestural similarity (cf. Articulatory Phonology) • PSE becomes apparent with overt articulation (Oppenheim and Dell, 2007) • Non-canonical errors

  29. Discussion speech tasks • Auditory feedback • Gestural adjustment to correct perceived speech error • Conventional PSE from participant’s self-generated auditory input • Cf. effect of similar auditory distractor in Saito and Baddeley study • Cf. stuttering literature on error-inducing properties of own speech (Stuart et al., 1996)

  30. Correlatory results • Descriptive stats and correlation matrix attached • Tongue-twister results correlate with • Serial repetition (r = -.527) • Serial matching (r = -.673) • Serial recall results also correlate with • Digit articulation time (r = -.671) • Age (r = -.570) • NWR no significant correlations

  31. Correlations discussion • Serial digit repetition and matching • Correlation suggests shared underlying factor(s) • Phonological planning ? • Saito and Baddeley (2004) factor analysis • Matching doesn’t require digit articulation motor execution • Correlation with digit articulation time • Serial digit recall relates to speed of subvocal articulatory rehearsal • S & B DAT relates to motor execution because more repetitions?

  32. Correlations discussion • NWR no correlation • No inter-rater reliability assessment • Individual variation in auditory discrimination • Novel stimulus -> greater reliance on auditory perception and processing abilities • Doesn’t tap same processes as vSTM measures • Sounds require novel phonological representation

  33. Correlations discussion • NWR no correlation • Contrary to findings of Hulme et al. (1991) • Hulme et al. familiarised participants with nonwords before testing • So nonwords already had long-term phonological representation and phonological-articulatory speech plan • Long-term memory contribution to serial recall tasks (& tongue-twister task?)

  34. Correlations discussion • vWM and speech errors • Higher digit span score associated with fewer speech errors • Replicates findings of Saito and Baddeley • Different explicit task demands of 2 error-elicitation paradigms • Correlation only exists for tasks involving real words • Items which are already represented within the lexicon • PSE in both error-elicitation tasks implicates store?

  35. Correlations discussion • vWM and speech errors • Speech error-rate doesn’t correlate with DAT • Although DAT involves articulation under pressure • Although DAT indicator of articulatory rehearsal rate (and hence capacity) • Does correlation of speech-error rate and vWM occur because performance on both tasks in predicated on robustness of verbal representations ?

  36. Discussion correlations • How? • Phonological representations vulnerable to interference at a phonological level (PSE) • Phonological representations subject to (limited) interaction from other levels of speech production system (e.g., Rapp & Goldrick, 2000) • Activation can be influenced by lexical information • Feedback from an articulatory level

  37. Discussion correlations • Evidence • Wilshire (1998) • Onset-effect for word but not nonword tongue-twisters indicates lexical-level contribution • Tehan and Lalor (2000) • Serial recall tasks involve lexical access • Hulme et al. (1991) • Serial recall better for newly-learnt words if participant learns sound + meaning

  38. Discussion correlations • Explanation of correlatory pattern? • Serial recall correlates with DAT because both predicated on speed of articulatory rehearsal • Serial recall correlates with error-rate because both predicated on strength of phonological representations

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