Models of word production and reaction-time evidence

Last week

3 stages to production: Conceptualisation Formulation Articulation

Formulation involves lexical retrieval: Semantic/syntactic content (lemma) Phonological content (word-form)

Tip of tongue state when lemma is retrieved without word-form being retrieved

This week

Levelt et al.’s theory of word productionModularity in language production Experimental evidence for this account

Dell’s interactive accountRecent experimental evidence that

supports interaction

Can the modular approach explain these results?

Levelt, Roelofs and Meyer’s (1999) model of

word production See two figures: theory outline and description of networkTheory outline: multiple levels of representation lack of feedback except via the monitor

Network has three strata conceptual stratum lemma stratum word-form stratum

                                                           

                   

                                                                                 

                 

TIGER (X)

Tigre

NounFem.

Countable

/tigre/

t i g

Lexical concept

lemma

Word form

phonemes

Has Stripes Is Dangerous

Conceptual stratum

Conceptual stratum is not decomposed thus, one lexical concept node for “escort”not decomposed into “walk”, “be with”,

“safeguard” instead, conceptual links from “escort” to

“safeguard”, etc.

Activation of concepts“pragmatically”, via the intention to communicate something (e.g., describing an object)together with “perspective” (e.g., using “dog” vs. “animal”)but also via spreading activation from other conceptsor via direct activation of that concept (e.g., the word “dog”)or perhaps via some random, spontaneous activation

Lexical selection

First, lemma activation occurs

This involves activating a lemma or lemmas corresponding to the concept thus, concept DOG activates lemma “dog”

but also involves activating other lemmas DOG also activates CAT (etc.) to some extent and CAT activates lemma “cat”

Lemma selection

Distinguished from activationOnly one lemma is selected (in this model)probability of selecting the target lemma (“dog”) is the ratio of that lemma’s activation to the total activation of all lemmas (“dog”, “cat”, etc.)hence competition between semantically related lemmascompetitors can be activated in other ways (see below)

Determining grammatical properties

Fixing “diacritic parameters” correspond to grammatical properties of the word include grammatical category (noun, verb, etc.) include number, person, tense, mood for verbs include number, person, gender, count/mass status for

nouns

DOGS leads to selection of “dog” lemma plus plural number and noun category parametersNote: function words can be selected on purely syntactic grounds e.g., that in John saw that is activated by saw

Morpho-phonological encoding (and beyond) (a very rough sketch)

The lemma is now converted into a phonological representation called “word-form” (or “lexeme”)

If “dog” lemma plus plural (and noun) are activated Leads to activation of morphemes dog and s

Morpheme = smallest meaningful unit of the language

Other late stages (in speaking)

Accessing metrical shape basically, syllable structure and stress pattern escort has two syllables and is stress-final

Accessing segmental make-up basically the phonemes that make up the word

e.g., /d/, /o/, /g/

Then a phonetic representation is constructed This specifies the articulatory task that will

produce the word

Finally, the word is articulated

A modular account

claim that processes are encapsulated, so that the output to a module depends only on its inputs

cf. The Modularity of Mind (Fodor, 1983) but Fodor didn’t really consider language

production

in production, modularity amounts to the claim that later processes cannot affect earlier processes

Levelt et al.’s model allows no feedback during encodingcritically, no feedback from word-form

stratum to lemma stratumcontrasts with Dell’s account (see below)

Also, only one lemma activates a word form if “dog” and “cat” lemmas are activated, they

compete to produce a winner at the lemma stratum

Only the “winner” activates a word form the word forms for the “losers” aren’t accessed hence, it doesn’t allow “cascading” activation

A rift between lemma and word form

Levelt et al.’s model assumes a clear divideonly one word (lemma) can “cross the

divide” between lemma and wordform strataand no feedback possible

Accords well with TOT and anomia data sometimes the divide cannot be crossed

Self-monitoring

listening to yourselfCorrecting yourselfCritical role in Levelt et al.’s model “external loop” monitoring what is said internal loop” monitoring the phonological

representation (probably)used to explain results that appear to be

due to feedback or cascading activation

Picture-word interference

Participants name basic objects as quickly as possible e.g., picture of a dog

Distractor words are embedded in the objecte.g., the word catparticipants are instructed to ignore these

words

A stroop-like effect

Basic finding that semantically related words can interfere with naminge.g., the word cat in a picture of a dog

However, form-related words can speed up processing e.g., the word dot in a picture of a dog

Experiments manipulate timing:picture and word can be presented

simultaneouslyor one can slightly precede the other

We draw inferences about time-course of processingand test word-production models

Schriefers, Meyer, and Levelt (1990)

Auditory presentation of distractors hence, definitely phonological (not orthographic)

effect

Conditions unrelated word SHIP phonologically related DOT

alliterative (i.e., same beginning)

semantically related CAT TARGET: DOG

SOA (Stimulus onset asynchrony) manipulation -150 ms (word …150 ms … picture) 0 ms (i.e., synchronous presentation) +150 ms (picture …150ms …word)

Results

Semantic effect:

-150 ms Word … 150 ms … Picture

inhibition (related slower than control)

0 ms, +150 ms Word = Picture; Picture …150 ms … Word

no effect

Results

Phonological effect:

- 150 ms: Word … 150 ms … Picture no effect

0 ms, +150 ms Word = Picture; Picture …150 ms … Word facilitation (related faster than control)

Picture/word interference: gender

Schriefers (1993): Picture/Word interference in Dutch. Distractors had either the same or a different gender

from the target noun (say tafel-comm): broek-comm/hemd-neuter

Target nouns were either named with a phrase or as a bare noun: de rode tafel or tafel

Gender congruency effect, but only if the entire phrase was named.

Interpretation: distractor boosts one of the two gender nodes. If selection necessary, possible effect.

Separate semantic and phonological stages?

Early semantic inhibition

Late phonological facilitation

Fits with the assumption that semantic processing precedes phonological processing

No overlap suggests two discrete stages in production an interactive account might find semantic and

phonological effects at the same time

Other studies support and extend these results other picture-word experiments (e.g.,

Meyer & Schriefers, 1991, JEP:LMC) other methods (e.g., Levelt et al., 1991;

Van Turrenout et al., 1998) but many other experiments criticise these

claims (see below)

Dell’s interactive account

Dell (1986) presented the best-known interactive account other similar accounts exist

3 levels of representationsemantics (decomposed into features)wordsphonemes (sounds)

Interactive because information flows “upwards” as well as “downwards” e.g., the semantic features mammal, barks, four-

legs activate the word “dog” this activates the sounds /d/, /o/, /g/ these send activation back to the word level,

activating words containing these sounds (e.g., “log”, “dot”) to some extent

this activation is upwards (phonology to syntax) and wouldn’t occur in Levelt’s account

Evidence: “Mixed” errors

Both semantic and phonological relationship to target wordTarget = “cat” semantic error = “dog” phonological error = “hat” mixed error = “rat”

Occur more often than predicted by modular models if you can go wrong at either stage, it would only

be by chance that an error would be mixed

Dell’s explanation the semantic features of dog activate lemma “cat” some features (e.g., animate, mammalian) activate “rat”

as well “cat” then activates the sounds /k/, /ae/, /t/ /ae/ and /t/ activate “rat” by feedback this confluence of activation leads to increased

tendency for “rat” to be uttered

Also explains the tendency for phonological errors to be real words Sounds can only feed back to words (non-words not

represented) so only words can feedback to sound level

Why might interaction occur?

Can’t exist just to produce errors! Perhaps because the same network is used in comprehension So feedback would be the normal

comprehension routeDell argues against this because many

aphasics have good auditory word recognition yet disturbed phonological encoding

Alternatively, it simply serves to increase fluency in lemma selection advantageous to select a lemma whose

phonological form is easy to find

Evidence for interactivity

A number of recent experimental findings appear to support interaction under some circumstances (or at least cascading models)Peterson & Savoy (JEP:LMC, 1998)Cutting & Ferreira (JEP:LMC, 1999)Griffin & Bock (JML, 1998)Damian & Martin (JEP:LMC, 1999)

Peterson & Savoy found evidence for phonological activation of near synonyms: Participants slower to say distractor soda than

unrelated distractor when naming couch Soda is related to non-selected sofa

remember that Levelt et al. assume that only one lemma can be selected and hence activate a phonological form

Levelt et al’s explanation: Could be erroneous selection of two lemmas?

Damian and Martin (1999)

Extension of Schriefers et al.’s picture-word interference task remember that semantic inhibition occurred

early, phonological facilitation occurred late (with no overlap)

various methodological changes and developments

focus on Experiment 3

The critical difference from Schriefers et al. is the addition of a “semantic and phonological” condition

Picture of Apple peach (semantically related) apathy (phonologically related) apricot (sem & phono related) couch (unrelated) (also no-word control, always fast)

Results

Relatedness -150 ms 0 ms + 150 ms

Unrelated 670 702 691

Semantic 702 733 697

Phono. 665 683 646

S & P 679 676 654

Summary of findings

early semantic inhibition (- 150 and 0 ms)

late phonological facilitation (0 and + 150 ms) shows overlap, unlike Schriefers et al.

but S & P condition didn’t show early semantic inhibition

This last finding demonstrates that semantic interference is reduced in the simultaneous presence of a phonological relationship (which should facilitate)

Thus the finding appears to contradict the “discrete two-step” account of Levelt et al.

Can the two-stage account be saved?

Evidence for interaction is hard to reconcile with the Levelt account however, most attempts are likely to

revolve around the monitorbasically, people sometimes notice a

problem and screen it outLevelt argues that evidence for interaction

really involves “special cases”, not directly related to normal processing

Summary

Levelt et al.’s theory of word production: Strictly modular lexical access Syntactic processing precedes phonological

processing

Dell’s interactive account: Interaction between syntactic and phonological

processing

Experimental evidence is equivocal, but increasing evidence that more than one lemma may activate associated wordform

Caramazza’s alternative

Caramazza and colleagues argue against the existence of the lemma node instead they propose a direct link between

semantic level and lexeme syntactic information is associated with the lexeme Also assumes separate lexemes for written and

spoken production This is really a different issue

Much evidence comes from patient data

But also evidence from the independence of syntactic and phonological information in TOT statessee discussion of Vigliocco et al. also Caramazza and Miozzo (Cognition,

1997; see also replies by Roelofs et al.)