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Perceptual Categories: Old and gradient, young and sparse.

Perceptual Categories: Old and gradient, young and sparse. Bob McMurray University of Iowa Dept. of Psychology. Collaborators. Richard Aslin Michael Tanenhaus David Gow. Joe Toscano Cheyenne Munson Meghan Clayards Dana Subik Julie Markant Jennifer Williams.

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Perceptual Categories: Old and gradient, young and sparse.

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  1. Perceptual Categories: Old and gradient, young and sparse. Bob McMurray University of Iowa Dept. of Psychology

  2. Collaborators Richard Aslin Michael Tanenhaus David Gow Joe Toscano Cheyenne Munson Meghan Clayards Dana Subik Julie Markant Jennifer Williams The students of the MACLab

  3. Categorization Categorization occurs when: 1) discriminably different stimuli… 2) …are treated equivalently for some purposes… 3) …and stimuli in other categories are treated differently.

  4. Categorization Perceptual Categorization • Continuous input maps to discrete categories. • Semantic knowledge plays minor role. • Bottom-up learning processes important.

  5. Categorization Perceptual Categorization • Continuous inputs map to discrete categories. • Semantic knowledge plays less of a role. • Categories include: • Faces • Shapes • Words • Colors • Exemplars include: • A specific view of a specific faces • A variant of a shape. • A particular word in a particular utterance • Variation in hue, saturation, lightness

  6. Categorization occurs when: 1) Discriminably different stimuli… 2) …are treated equivalently for some purposes… 3) …and stimuli in other categories are treated differently. Premise For Perceptual Categoriesthis definition largely falls short. and this may be a good thing. Approach Walk through work on speech and category development. Assess this definition along the way.

  7. Overview • Speech perception: Discriminably different and categorical perception. • Word recognition: exemplars of the same word are not treated equivalently.(+Benefits) 3) Speech Development: phonemes are not treated equivalently. • Speech Development (model): challenging other categories treated differently. (+Benefits) 5) Development of Visual Categories: challenging other categories treated differently.

  8. Categorical Perception B 100 100 Discrimination % /p/ Discrimination ID (%/pa/) 0 0 B VOT P • Sharp identification of tokens on a continuum. P • Discrimination poor within a phonetic category. Subphonemic variation in VOT is discarded in favor of adiscretesymbol (phoneme).

  9. Categorical Perception Categorical Perception: Demonstrated across wide swaths of perceptual categorization. Line Orientation (Quinn, 2005) Basic Level Objects (Newell & Bulthoff, 2002) Facial Identity (Beale & Keil, 1995) Musical Chords (Howard, Rosen & Broad, 1992) Signs (Emmorey, McCollough & Brentari, 2003) Color (Bornstein & Korda, 1984) Vocal Emotion (Luakka, 2005) Facial Emotion (Pollak & Kistlerl, 2002) What’s going on?

  10. Categorical Perception • Across a category boundary, CP: • enhances contrast. • Within a category, CP yields • a loss of sensitivity • a down-weighting of the importance of within-category variation. • discarding continuous detail.

  11. Categorical Perception • Across a category boundary, CP: • enhances contrast. • Within a category, CP yields • a loss of sensitivity • a downweighting of the importance of within-category variation. • discarding continuous detail. Categorization occurs when: 1) discriminably different stimuli… 2) …are treated equivalently for some purposes… 3) …and stimuli in other categories are treated differently Stimuli are not discriminably different. CP: Categorization affects perception. Definition: Categorization independent of perception. Need a more integrated view…

  12. Perceptual Categorization Categorization occurs when: CP: perception not independent of categorization. • discriminably • different stimuli • 2) are treated • equivalently for • some purposes… • and stimuli in • other categories • are treated • differently.

  13. Categorical Perception • Across a category boundary, CP: • enhances contrast. • Within a category, CP yields • a loss of sensitivity • a downweighting of the importance of within-category variation. • discarding continuous detail. Is continuous detail really discarded?

  14. Is continuous detail really discarded? Evidence against the strong form of Categorical Perception from psychophysical-type tasks: Sidebar This has never been examined with non-speech stimuli… • Goodness Ratings • Miller (1994, 1997…) • Massaro & Cohen (1983) • Discrimination Tasks • Pisoni and Tash (1974) • Pisoni & Lazarus (1974) • Carney, Widin & Viemeister (1977) • Training • Samuel (1977) • Pisoni, Aslin, Perey & Hennessy (1982)

  15. Is continuous detail really discarded? No. ? Why not? Is it useful?

  16. X basic bakery bakery X ba… kery barrier X X bait barricade X baby • Online Word Recognition • Information arrives sequentially • At early points in time, signal is temporarily ambiguous. • Later arriving information disambiguates the word.

  17. Input: b... u… tt… e… r time beach butter bump putter dog

  18. These processes have been well defined for a phonemic representation of the input. But considerably less ambiguity if we consider within-category (subphonemic) information. Example: subphonemic effects of motor processes.

  19. Coarticulation n n ee t c k Any action reflects future actions as it unfolds. Example:Coarticulation Articulation (lips, tongue…) reflectscurrent, futureandpastevents. Subtle subphonemic variation in speech reflects temporal organization. Sensitivity to theseperceptualdetails might yield earlier disambiguation.

  20. Experiment 1 ? What does sensitivity to within-category detail do? Does within-category acoustic detail systematically affect higher level language? Is there a gradient effect of subphonemic detail on lexical activation?

  21. Experiment 1 Gradient relationship: systematic effects of subphonemic information on lexical activation. If this gradiency is used it must be preserved over time. Need a design sensitive to bothsystematic acoustic detailand detailedtemporal dynamicsof lexical activation. McMurray, Tanenhaus & Aslin (2002)

  22. Acoustic Detail Use a speech continuum—more steps yields a better picture acoustic mapping. KlattWorks:generate synthetic continua from natural speech. • 9-step VOT continua (0-40 ms) • 6 pairs of words. • beach/peach bale/pale bear/pear • bump/pump bomb/palm butter/putter • 6 fillers. • lamp leg lock ladder lip leaf • shark shell shoe ship sheep shirt

  23. Temporal Dynamics How do we tap on-line recognition? With an on-line task:Eye-movements Subjects hear spoken language and manipulate objects in a visual world. Visual world includes set of objects with interesting linguistic properties. abeach, apeachand some unrelated items. Eye-movements to each object are monitored throughout the task. Tanenhaus, Spivey-Knowlton, Eberhart & Sedivy, 1995

  24. Why use eye-movements and visual world paradigm? • Relatively naturaltask. • Eye-movements generated veryfast(within 200ms of first bit of information). • Eye movementstime-lockedto speech. • Subjectsaren’t awareof eye-movements. • Fixation probability maps ontolexical activation..

  25. Task A moment to view the items

  26. Task Bear Repeat 1080 times

  27. Identification Results 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 5 10 15 20 25 30 35 40 High agreement across subjects and items for category boundary. proportion /p/ B VOT (ms) P By subject:17.25 +/- 1.33ms By item: 17.24 +/- 1.24ms

  28. Task 200 ms Trials 1 2 3 4 5 % fixations Time Target = Bear Competitor = Pear Unrelated = Lamp, Ship

  29. Task 0.9 VOT=0 Response= VOT=40 Response= 0.8 0.7 0.6 0.5 Fixation proportion 0.4 0.3 0.2 0.1 0 0 400 800 1200 1600 2000 0 400 800 1200 1600 Time (ms) More looks to competitor than unrelated items.

  30. Task target Fixation proportion Fixation proportion time time • Given that • the subject heard bear • clicked on “bear”… How often was the subject looking at the “pear”? Categorical Results Gradient Effect target target competitor competitor competitor competitor

  31. Results 20 ms 25 ms 30 ms 10 ms 15 ms 35 ms 40 ms 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 0 400 800 1200 1600 0 400 800 1200 1600 2000 Response= Response= VOT VOT 0 ms 5 ms Competitor Fixations Time since word onset (ms) Long-lasting gradient effect: seen throughout the timecourse of processing.

  32. 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0 5 10 15 20 25 30 35 40 Area under the curve: Clear effects of VOT B: p=.017* P: p<.001*** Linear Trend B: p=.023* P: p=.002*** Response= Response= Looks to Competitor Fixations Looks to Category Boundary VOT (ms)

  33. 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0 5 10 15 20 25 30 35 40 Unambiguous Stimuli Only Clear effects of VOT B: p=.014* P: p=.001*** Linear Trend B: p=.009** P: p=.007** Response= Response= Looks to Competitor Fixations Looks to Category Boundary VOT (ms)

  34. Summary Subphonemic acoustic differences in VOT have gradient effect on lexical activation. • Gradient effect of VOT on looks to the competitor. • Effect holds even for unambiguous stimuli. • Seems to be long-lasting. Consistent with growing body of work using priming (Andruski, Blumstein & Burton, 1994; Utman, Blumstein & Burton, 2000; Gow, 2001, 2002). Variants from the same category are not treated equivalently: Gradations in interpretation are related to gradations in stimulus.

  35. Extensions Word recognition is systematically sensitiveto subphonemic acoustic detail. • Voicing • Laterality, Manner, Place • Natural Speech • Vowel Quality

  36. Extensions B Sh L P Word recognition is systematically sensitiveto subphonemic acoustic detail. • Voicing • Laterality, Manner, Place • Natural Speech • Vowel Quality  Metalinguistic Tasks

  37. Extensions 0.1 Response=P Looks to B 0.08 0.06 Competitor Fixations Response=B Looks to B 0.04 Category Boundary 0.02 0 0 5 10 15 20 25 30 35 40 VOT (ms) Word recognition is systematically sensitiveto subphonemic acoustic detail. • Voicing • Laterality, Manner, Place • Natural Speech • Vowel Quality  Metalinguistic Tasks

  38. Extensions 0.1 0.08 0.06 0.04 0.02 0 Word recognition is systematically sensitiveto subphonemic acoustic detail. • Voicing • Laterality, Manner, Place • Natural Speech • Vowel Quality  Metalinguistic Tasks Response=P Looks to B Competitor Fixations Response=B Looks to B Category Boundary 0 5 10 15 20 25 30 35 40 VOT (ms)

  39. Categorical Perception Within-category detail surviving to lexical level. Abnormally sharp categories may be due to meta-linguistic tasks. There is a middle ground: warping of perceptual space (e.g. Goldstone, 2002) Retain: non-independence of perception and categorization.

  40. Perceptual Categorization Categorization occurs when: CP: perception not independent of categorization. • discriminably • different stimuli Exp 1: Lexical variants not treated equivalently (gradiency) • 2) are treated • equivalently for • some purposes… • and stimuli in • other categories • are treated • differently.

  41. Perceptual Categorization Categorization occurs when: CP: perception not independent of categorization. • discriminably • different stimuli Exp 1: Lexical variants not treated equivalently (gradiency) • 2) are treated • equivalently for • some purposes… WHY? • and stimuli in • other categories • are treated • differently.

  42. Progressive Expectation Formation Any action reflects future actions as it unfolds. • Can within-category detail be used to predict future acoustic/phonetic events? • Yes: Phonological regularities create systematic within-category variation. • Predicts future events.

  43. Input: m… a… r… oo… ng… g… oo… s… time maroon goose goat duck Experiment 3: Anticipation Word-final coronal consonants (n, t, d) assimilate the place of the following segment. Maroong Goose Maroon Duck Place assimilation -> ambiguous segments —anticipate upcoming material.

  44. We should see faster eye-movements to “goose” after assimilated consonants. Subject hears “select the maroonduck” “select the maroon goose” “select the maroong goose” “select the maroong duck” *

  45. Onset of “goose” + oculomotor delay 0.9 0.8 0.7 0.6 Fixation Proportion 0.5 0.4 Assimilated 0.3 Non Assimilated 0.2 0.1 0 0 200 400 600 Time (ms) Looks to “goose“ as a function of time Results Anticipatory effect on looks to non-coronal.

  46. Onset of “goose” + oculomotor delay 0.3 Assimilated 0.25 Non Assimilated Fixation Proportion 0.2 0.15 0.1 0.05 0 0 200 400 600 Time (ms) Looks to “duck” as a function of time Inhibitory effect on looks to coronal(duck, p=.024)

  47. Experiment 3: Extensions Possible lexical locus Green/m Boat Eight/Ape Babies Assimilation creates competition

  48. Sensitivity to subphonemic detail: • Increase priors on likely upcoming events. • Decrease priors on unlikely upcoming events. • Active Temporal Integration Process. • Possible lexical mechanism… NOT treating stimuli equivalently allows within-category detail to be used for temporal integration.

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