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Accessing spoken words: the importance of word onsets

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Accessing spoken words: the importance of word onsets William Marslen-Wilson and Pienie Zwitserlood Presented by: Qinghua Tang Introduction Natural speech differs ... – PowerPoint PPT presentation

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Title: Accessing spoken words: the importance of word onsets


1
Accessing spoken words the importance of word
onsets
  • William Marslen-Wilson and Pienie Zwitserlood
  • Presented by Qinghua Tang

2
Introduction
  • Natural speech differs from written language in
    its directionality in time. When we hear natural
    speech, we hear it along a time line.
  • Does this mean we access words in our mental
    lexicon along the time line as well?

3
Two different models
  • Cohort model by Marslen-Wilson, 1984
  • Based on the acoustic-phonetic properties, an
    initial set of candidates are activated. For
    example, when t is heard, all the words that
    start with t will be activated.
  • Incoming input helps to eliminate candidates
    until one is chosen.
  • Emphasis on the beginnings of words
  • TRACE model by Elman and McClelland, 1986
  • Three levels features, phonemes, and words
  • Relevant nodes are activated as the incoming
    speech is matched to relevant nodes and will
    keep being activated until the successful access
    of the word.
  • A word is accessed when the activation reaches a
    certain level.
  • Emphasis on the overall goodness of fit between
    the complete stimulus and a given lexical
    representation.
  • E.g. bleasure can be identified as pleasure
    because of the overall activation level.
  • Directionality is not an explicit condition

4
Previous research
  • Earlier research has shown the effects of
    word-initial partial matches (e.g.
    Marslen-Wilson, et al., 1989).
  • Stimuli word pairs starting with same segments.
    The average number of shared segments was 3.3.
  • For example, kapitein (meaning captain in
    Dutch) and kapitaal (meaning capital in Dutch)
  • Procedure in the experiment, subjects heard
    prime words like kapitein and kapitaal and
    saw a word that was either related to kapitein
    (e.g BOOT, meaning ship ) or kapitaal (e.g
    GELD, meaning money). The subjects were
    instructed to press a button to make lexical
    decisions to the word they see.
  • Results when the probe word (visual word) was
    presented during the t of kapitein, both the
    word related to kapitein and the word related
    to kapitaal were facilitated.

5
  • Previous research shows that partial match can
    activate lexical representations, but,
  • Will partial match activate lexical
    representations if the partial match starts late
    in the word rather than the beginning of the
    word?

6
Research questions
  • Is there a strong temporal directionality in
    lexical access?
  • Does the on-line decision process tolerate later
    entry into the decision space of candidates that
    mismatch early in the word?

7
Experiment design - subjects
  • 60 native speaker of Dutch. The subjects were
    randomly assigned to one of the experimental
    versions, six subjects per version.

8
Experiment design 5 experimental conditions
  • Original-word condition a word and its semantic
    associate (e.g. honing, meaning honey, and bij,
    meaning bee)
  • there was a complete match between acoustic
    stimulus and lexical element
  • a baseline
  • Real-word rhyme condition the prime word rhymes
    with the prime word in the original-word
    condition (e.g. woning, meaning dwelling, and
    bij, meaning bee)
  • A partial match between woning and honing
  • In this case, woning should obviously be
    activated. Will honing, which rhymes with it,
    also be activated? If so, the access of bij
    should be facilitated.

9
  • Nonword rhyme condition the prime word was a
    non-word that rhymed with the the prime word in
    the original-word condition (e.g foning and bij)
  • A partial match condition
  • This condition was included to address one
    concern from the TRACE model once a word like
    woning was heard, it might inhibit the
    activation of its competitors such as honing. A
    non-word was therefore needed.
  • Two control conditions were used real-word
    control condition (e.g. pakket and bij) and
    nonword control condition (e.g. dakket and bij)
  • In order to match with both real word and nonword
    conditions

10
Experiment design - materials
  • 50 sets of rhyming pairs (such as honing /
    woning) and their associated visual probes.
  • Each of the 50 sets was assigned to a different
    version of the experiment. For example, in the
    new version, woning would become the original
    prime, a new word HUIS (meaning house) would be
    used as the probe. Honing would become the
    real-word prime in this case.
  • 150 sets of filler pairs were added, balanced for
    word / nonword types. The lengths of the words
    were matched to real test targets.

11
Experiment design - procedure
  • The subjects were instructed to listen carefully
    to the spoken materials ( the prime words) and
    decide, as quickly as possible, whether the
    string of letters that was presented visually
    after each spoken word was a real word or not.

12
Results
13
Results
  • Only the original-word condition, in which there
    was a complete match between the input and the
    word associated with the visual probe, produced
    significant priming effects (32 ms).
  • In neither of the two partial match conditions
    was there any significant facilitation (11 ms for
    real-word rhyme condition, 4 ms for nonword rhyme
    condition).
  • The absolute reaction times for the two partial
    match conditions were almost identical (547 vs.
    548 ms).
  • However, rhyme primes did have some effect on the
    lexical representations of items with which they
    rhyme, even if this produceed only small
    facilitation.

14
Discussion amount of segmental overlap
  • Could the failure of partial match in producing
    significant facilitation be caused by lack of
    sufficient overlap between real-word primes and
    the original words?
  • Stimuli were divided into four categories,
    depending on the number of shared segments which
    ranges from 3 to 6 or more)
  • The number of items in each overlap group
  • 16 items in 3 segment group
  • 48 items in 4 segment group
  • 12 items in 5 segment group
  • 16 items in 6 or more segment group
  • The average segment overlap for previous
    experiments was between 2.9 and 3.3.

15
Figure 2 segment overlap effects
16
  • There was a significant effect of prime type, but
    no effect of length.
  • The degree of activation of a lexical
    representation seemed to be independent of the
    amount of overlapping segments.
  • These results make it unlikely that the failure
    of rhyme primes to produce facilitation was
    because they did not provide amounts of matching
    input comparable to the word initial primes in
    the previous experiment.

17
Discussion the competitor environment
  • Does the number of competitors matter?
  • In current models of lexical access, the number
    of competitors that a prime word has to contend
    with plays an important role in determining the
    response of the system.
  • the current stimulus sets varied in the number of
    rhyme competitors from 1 to 23.
  • 30 sets had only 1 rhyme competitor (I.e. the
    matched real-word rhyme). The other 70 sets had
    rhyme competitors ranging from 2 to 23.
  • the stimuli were divided into 3 groups
  • 30 sets with 1 competitor, 30 sets with 2 to 4
    competitors, and 30 sets with 6 to 23 competitors

18
Figure 3
19
  • Variations in the number of competitors did not
    affect the advantage of full primes over rhyme
    primes, further confirming the overall advantage
    of the directionality hypothesis.
  • On the other hand, the competitor environment
    did seem to matter. When the competition was low,
    the overall level of activation was higher for
    both the complete match and partial match
    conditions.

20
Conclusion
  • The dominant effect in the present results is
    directionality of mapping. Primes that mismatched
    at the beginning of the word with the relevant
    lexical form representation were always less
    effective than primes that did not mismatch word
    initially. This suggests that word onsets do have
    a special status in spoken word recognition.
  • There was no detectable effect of the lexical
    status of the rhyme prime. The real-word rhyme
    and nonword rhyme prime stimuli behaved the same
    way throughout.
  • Partial match that starts late in the word rather
    than the beginning also shows facilitation
    effects and it interacts with the density of the
    competitor environment. More research is needed
    to account for this fact.

21
  • Thank you!
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