david b. pisoni (1976-77)

35
Identification and discrimination of the relative onset time of two component tones: Implications for voicing perception in stops David B. Pisoni (1976-77)

Upload: mabyn

Post on 10-Feb-2016

38 views

Category:

Documents


0 download

DESCRIPTION

Identification and discrimination of the relative onset time of two component tones: Implications for voicing perception in stops. David B. Pisoni (1976-77). Past Studies. Lisker and Abramson (1964, 1970) Liberman et al. Mattingly, Liberman, Sydral, and Halwes Eimas (1971) - PowerPoint PPT Presentation

TRANSCRIPT

Page 1: David B. Pisoni (1976-77)

Identification and discrimination of the relative onset time of two component

tones: Implications for voicing perception in stopsDavid B. Pisoni (1976-77)

Page 2: David B. Pisoni (1976-77)

Past Studies

• Lisker and Abramson (1964, 1970)• Liberman et al.• Mattingly, Liberman, Sydral, and Halwes• Eimas (1971)• Kuhl Miller (1975)• Lasky• Streeter• Miller et al

Page 3: David B. Pisoni (1976-77)

Lisker and Abramson

• They investigated – Voicing and aspiration differences shown across different

languages (last class)– Differences in timing and glottal activity

• They discovered 3 modes of voicing (1964):– Pre-voiced stops = voicing onset precedes the release burst

(negative onset, -VOT)– Short-lag voiced stops = voicing onset is simultaneous or

briefly lags behind the release burst (0 VOT)– Long-lag voiceless stops in which the voicing onset lags

behind the release burst (positive onset, +VOT)

Page 4: David B. Pisoni (1976-77)

Liberman

• In perceptual experiments done with synthetic stimuli* they found (1961)…– Subjects ID and discriminate differences in VOT in

a categorical-like manner that reflects the phonological categories* of their language

– Consistent labeling with sharp crossover points – Discontinuities in discrimination that are correlated

with the abrupt changes in the labeling functions– Better at discriminating 2 synthetic stimuli from 2

different phonological categories vs. from the the same

Page 5: David B. Pisoni (1976-77)

According to Several

• Empirical Findings– Non-speech signals are perceived in a continuous

mode– No other categorical perception studies had been

done with synthetic stimuli– Non-monotonic discrimination functions are the

result of labeling processes associated with phonetic categorization

• Interpretation– Evidence for the operation of a special mode of

perception…Speech Mode

Page 6: David B. Pisoni (1976-77)

Liberman et al. (1961) & Mattingly, Liberman, Syrdal

and Halwes (1971)• Are discontinuities in speech discrimination functions

due to the acoustic or psychophysical* attributers of the signals themselves rather than some speech related labeling process?

• Found no peaks in the non-speech discrimination functions at phoneme boundaries so…

• Conclusion = Speech Mode – discrimination of speech stimuli were attributable

to phonetic categorization resulting from the stimuli being perceived as speech.

Page 7: David B. Pisoni (1976-77)

Eimas (1971)• 2 and 3 month old infants• Found that they can discriminate synthetic

speech sounds varying in VOT much like English speaking adults

• Implication = infants have access to mechanisms of phonetic categorization

• Innate mechanisms• Responding to phonetic coding VS.

psychophysical differences• Environment plays a secondary role

Page 8: David B. Pisoni (1976-77)

Kuhl and Miller (1975)• Study done with chinchillas• Trained to respond differently to the consonants /d/ and /t/

(human voice)• Used synthetic stimuli varying in VOT with a sharp

crossover point• The discrimination functions were similar to English

speaking human data…but chinchillas don’t have spoken language

• Suggests a psychophysical basis VS. phonetic basis for the labeling behavior

• Results = the boundary for voiced and voiceless labial stops occurs at about +25 msec…threshold

Page 9: David B. Pisoni (1976-77)

Lasky et al. (1975)• Cross-language studies• 4 to 6 1/2 month old infants born to Spanish-speaking

parents• Found evidence for 3-categories in discrimination

– Boundary occurred in the region of +20 msec and +60 msec (corresponds to the English voiced/voiceless times)

– And at -20 msec and -60 msec • Spanish only has one phoneme boundary b/w voiced

and voiceless stops and it does not coincide with the boundaries they found

• Conclusion: – Environment plays minor role– Responding to psychophysical attributes

Page 10: David B. Pisoni (1976-77)

Streeter (1976)

• Kikuyu infants (Kenya)• Show evidence of 3 categories of voicing for

labial stops• Kikuyu have no voicing contrasts for labial stops

(but they exist at other articulation places)• Conclusion:

– They had not been exposed to these before– Responding to psychophysical attributes– Similar to the Laskey et al. research

Page 11: David B. Pisoni (1976-77)

Miller et al. (1976)• Non-speech control signals

– Using VOT in the form of a noise bust and a buzz• Adults• Results: discrimination functions that were

similar to those found with stop consonants differing in VOT– Discrimination was excellent for stimuli selected

from b/w categories and poor for stimuli within a category

• Perceptual threshold• Psychophysical account

Page 12: David B. Pisoni (1976-77)

Pisoni

• Independent from Miller et al. but at the same time

• Used stimuli that varied in temporal order of the onsets of 2 component tones at 2 frequencies (Figure 1):– 500 Hz– 1500 Hz– -50, 0, +50 msec VOT (ranging in 10 msec

increments)

Page 13: David B. Pisoni (1976-77)

Pisoni

• Goals:– To learn something about how the timing

relations in stop consonants are perceived– To provide a more general account of the

diverse findings obtained with adults, infants and chinchillas on VOT stimulus

– To provide an account of the results obtained with non-speech stimuli

Page 14: David B. Pisoni (1976-77)

Pisoni: Experiment I• 8 paid volunteers from ad in student paper• All were right handed and native English

speakers• Stimuli (Figure 1):

– 11 digital two-tone sequences– Lower tone = 500 Hz– Higher tone = 1500 Hz– Variable is VOT

• -50• 0• +50

Page 15: David B. Pisoni (1976-77)

Pisoni: Experiment I• Stimuli was presented at 80 dB SPL• 2 one-hour sessions done over 2 days• Day one:

– Identification training sequences– Presented with the endpoint stimuli (-50 & +50)– Told to learn (w/their own strategy) which one of

the 2 buttons was associated w/ea sound– Immediate feedback for correct responses

Page 16: David B. Pisoni (1976-77)

Pisoni: Experiment I• Day two:

– Tested for identification• 11 stimuli presented in random order• No feedback

– Tested for ABX discrimination*• 9 two-step pairs along the continuum• Feedback provided for correct responses• Told to determine whether the 3rd sound (X) was most

like the first (A) or second (B) sound• Chance performance

Page 17: David B. Pisoni (1976-77)

Pisoni: Experiment I• Figure 2 (p.1355)

– Filled in circles = labeling functions response to 2 end points

• Sharp and consistent for some

• Crossover points for the category boundary for 6 of the 8 are not at 0 but are displaced towards the lagging (+50) stimuli– Why?

Page 18: David B. Pisoni (1976-77)

Pisoni: Experiment I• Possibly due to limitation on the processing of

temporal information or…• Due to Masking of the high frequency (1500

Hz) by the low (500 Hz)– So, they accounted for that by running a pilot study

• Pilot study (p.1355-56)– Results: they found no shift in boundary location

so…the Limitation on the Processing of Temporal Information is the more like cause of asymmetry

Page 19: David B. Pisoni (1976-77)

Pisoni: Experiment I

• ABX-discrimination results– Open circles Fig. 2– Categorical-like discrimination– Peaks and troughs– S2 ideal

Page 20: David B. Pisoni (1976-77)

Pisoni: Experiment I• Results from ID and ABX:

– Categorical perception with non-speech signals – This form of perception is not unique to speech

signals– Removes one positive line of evidence for the

Speech Mode theory• Questions:

– Are the findings due to labeling process brought about by the training process?

– Or is it do to a simpler psychophysical explanation?

Page 21: David B. Pisoni (1976-77)

Pisoni: Experiment II• Goal (in order to answer the previously asked

questions):– To obtain ABX-discrimination functions before any

training experience (label training)– If peaks in discrimination exist there will be reason

to suspect a psychophysical basis for the observed discrimination functions from E1

Page 22: David B. Pisoni (1976-77)

Pisoni: Experiment II• 12 volunteers• Same 11 stimuli used in E1• 2 one-hour sessions held on separate

days (no label training)• 360 ABX trials done ea. day with

feedback• 9 two-step stimuli comparisons were

responded to 80x by ea subject

Page 23: David B. Pisoni (1976-77)

Pisoni: Experiment II• Results:

– Figure 3 (p. 1357)– 2 patterns shown (except S1 = chance)

• Single peak @ approximately +20 msec• Double peak @ approximately +20 and -20

– Natural categories are present at places along the stimulus continuum marked by narrow regions of high sensitivity (thresholds)

– 3 categories corresponding with the temporal events• Lower tone leading by 20 msec or more (-)• More or less simultaneously within the -20 to +20 msec region• Lower tone lags by 20 msec or more (+)

Page 24: David B. Pisoni (1976-77)

Pisoni: Experiment II• These results contrast:

– Liberman et al. (1961)– Mattingly et al. (1971)

• The above both found:– Marked differences in discrimination

between speech and non-speech signals– Why?

Page 25: David B. Pisoni (1976-77)

Pisoni: Experiment II• The lack of familiarity with the stimuli used

(Liberman = synthetic spectograms of /do/ and /to/; Mattingly = 2nd formant transitions were isolated from the rest of the stimulus pattern)

• The absence of any feedback during the discrimination task

• With complex multidimensional signals it may be difficult for subjects to attend to the relevant attributes that distinguish these stimuli

Page 26: David B. Pisoni (1976-77)

Pisoni: Experiment II

• Patterns of categorical perception are seen when using speech and non-speech stimuli

Page 27: David B. Pisoni (1976-77)

Pisoni: Experiment III

• Goal:– To demonstrate that subjects can classify

these same stimuli into three distinct categories whose boundaries occur at precisely these regions on the continuum

Page 28: David B. Pisoni (1976-77)

Pisoni: Experiment III

• Same training procedure– Except…3 responses instead of 2

• 8 additional subjects were recruited• Same set of 11 tonal stimuli• Took place on 2 separate days

Page 29: David B. Pisoni (1976-77)

Pisoni: Experiment III• Day 1

– Shaping and identification training with the 3 stimuli (-50, 0, +50 msec)

– Subjects were free to adopt their own coding strategies

– Immediate feedback was provided• Day 2

– Labeling tests were conducted

Page 30: David B. Pisoni (1976-77)

Pisoni: Experiment III• Figure 4 (p. 1358)

– All subjects partitioned the stimulus continuum into three well-defined categories

– Boundaries found at approximately -20 and +20 msec

– Perceptual threshold– Ability to discriminate temporal

differences

Page 31: David B. Pisoni (1976-77)

Pisoni: Experiment IV

• Goal:– Simultaneous vs. non-simultaneous….– Having the subjects determine whether

there are one or two distinct events at stimulus onset

Page 32: David B. Pisoni (1976-77)

Pisoni: Experiment IV• 8 additional volunteers• None had participated previously• Same 11 tonal stimuli• A single 1-hour session• 11 stimuli presented randomly• Told to listen to ea sound carefully and then

determine whether they could hear one or two events at stimulus onset

• No feedback was given

Page 33: David B. Pisoni (1976-77)

Pisoni: Experiment IV• Figure 5 (p. 1359)

– All subjects showed similar U-shaped functions with sharp crossover points between categories

• Results:– The presence of 3 natural categories that may be

distinguished by the relative discriminability of the temporal order of the component events

Page 34: David B. Pisoni (1976-77)

Pisoni Findings

• A perceptual effect for processing temporal order information which may also underlie the perception of voicing distinctions in stop consonants in initial position

• There is a perceptual threshold (consistent with studies done by Hirsh, Hirsh and Sherrick, and Stevens and Klatt) of about 20 msec

Page 35: David B. Pisoni (1976-77)

Pisoni Findings• We know…that VOT (in terms of onset of voicing) must

be judged in relation to the temporal attributes of other events (release from closure)

• So, these events are ordered in TIME, therefore highly distinctive and discriminable changes will be produced at various regions along the temporal continuum

• Phonological systems apparently have exploited the principle of discriminating discrete attributes (natural categories) during the evolution of language

• In other words, we’ve positioned our phonemes on either side of the natural auditory boundary provided by the threshold