1 / 27

Speech Perception in Infants Peter D. Eimas et al. 1974

kovit
Download Presentation

Speech Perception in Infants Peter D. Eimas et al. 1974

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

    1. Speech Perception in Infants Peter D. Eimas et al. (1974) Ricardo Tabone LIN7901

    2. Not exactly like this….

    3. Purpose Test speech signal discrimination in infants Age groups: 1 month old and 4 months old Compare infant perception to adult perception Type of stimulus selected: VOT continuum

    4. Why VOT? Universal continuum Boundaries are not arbitrary There are three universal categorical boundaries along VOT Intuitively: Negative VOT: Pre-voicing (e.g., Thai) Short lag VOT (all languages) More Positive VOT (most languages) English uses only the last two categories (p)/(b)

    5. Figure 1: /ba/ vs. /pa/

    6. How do we know what the baby knows? Babies have a sucking reflex. Babies react to a new stimulus by accelerating the sucking reflex They attached a pressure sensor to a blind nipple to measure sucking responses However, after a few minutes, habituation sets in and sucking rate decreases Important: calculate the baseline sucking rate such that it’s possible to notice an acceleration

    7. How is it related to ERPs? In a nutshell: Sucking rate increase mimics MMN Finding a baseline sucking rate mimics averaging out the random brainwaves in EEG recording

    8. Experiment The babies were placed on their backs A speaker behind the baby’s head delivered sounds at variable amplitudes Amplitudes was controlled by sucking rate: slower sucking rate? louder stimulus Need to counteract natural habituation The first stimulus in a pair was repeated for about 5 minutes. Then the second one for 4 minutes.

    9. Stimuli: /ba/ to /pa/ VOTS: -20, 0, +20, +40, +60, and +80ms Perceived as /b/ in English: -20, 0, +20 Perceived as /p/ in English: +40, +60, +80 Eimas had already discovered that babies could distinguish differences of 20ms in VOT So, these differences were adequate for phonemic discrimination

    10. Stimuli conditions: 20D: Pair of stimuli with VOT 20ms apart. +20ms (/ba/) and +40ms (/pa/) Different phonemic categories 20S: Pair of stimuli with VOT 20ms apart. -20ms (/ba/) and 0ms (/ba/) +60ms (/pa/) and 80ms (/pa) Same phonemic category 0: Pair of identical stimuli (Control condition) Selected randomly for all subjects

    11. Subjects: 20D: 8 subjects of each age group 20S: 8 subjects of each age group 0: 10 subjects of each age group Total: 52 poor little babies!

    12. Results 20D: Significant increase of sucking rate after stimulus shift = Discrimination of phonemic category 20S: No discrimination Non significant decrease of sucking rate after stimulus shift (4-month olds) Non significant increment of sucking rate after stimulus shift (1-month olds) 0: Natural habituation progress.

    13. Figure 2: Sucking Responses

    14. Figure 3: Changes in Response Rate

    15. Conclusion: Infants as young as 1 month have: Categorical discrimination: Even with no linguistic experience! This ability must be biologically encoded However, not capable of discriminating within categories.

    16. The End

    17. The Discrimination of Foreign Speech Contrasts by Infants and Adults Sandra Trehub et al. (1976)

    18. Experiments: Infants 5-17 weeks old: Contrasts: [pa] x [pă] (French/Polish) (Experiment I) [za] x [ra] (Czech) (Experiment II) Adults (Experiment III) Contrasts: [ri] x [li] (English) [za] x [ra] (Czech)

    19. Experiments: Experiments I and II: 20 subjects for each experiment: No babies from French/Polish homes (Experiment I) No babies from Czech/Slavic homes (Experiment II) Stimuli: 4 different recordings of each sound on a tape Stimulus length = ~500ms ISI: ~500ms (1s – stimulus length) [pa] x [pă] recorded by French speaker (Experiment I) [za] x [ra] recorded by Czech speaker (Experiment II)

    20. Experiments: Experiments I and II: Design: Control Subjects: no sound change Experimental subjects: sound change after x minutes x = time at which sucking rate drops by 1/3 for 2 mins Sounds were played on a continuous loop: (1 _ 2 _ 3 _ 4 _ 1 _ etc) Until the moment of sound change

    21. Experiment I and II Results: Results: Infants can discriminate foreign language contrasts Figure 1: Percentage of maximum sucking rate (y-axis) Time, aligned by sound change (x-axis) Significant different between control and experimental subjects

    22. Figure 1: Categorical Discrimination

    23. Experiment III: Subjects: 10 university psychology students (U of T): Native speakers of English Some exposure to a foreign language (not Czech) Stimuli: 16 trial series Each trial: 10 sounds randomly separated by 1,2,3,4 or 5 seconds. [li] x [ri] recorded by English speaker [za] x [ra] recorded by Czech speaker (same as Exp. II)

    24. Experiment III: Stimuli: Sound change at random position (>= 3rd position) E.g.: AAAAAAAAAA (no change) AAABBBBBBB (change at 3) BBBBAAAAAA (change at 4) BBBBBBBBBB (no change) Inter-Trial Interval: 10 seconds

    25. Experiment III: Procedure: Indicate whether there was a sound change Indicate confidence level (1 to 4) 1 = guessing; 4 = very sure Results: d’ = .83 for Czech; Confidence = 2.58 (change); 2.50 (no-change) d’ = ? for English Confidence = 4.00 (change); 3.92 (co-change)

    26. Results: English and Czech

    27. Conclusion: Infants 5-17 weeks old have: Categorical discrimination of foreign contrasts. Adults: Confused by foreign contrast. Above chance discrimination, but babies are better. Infants must be using “low level auditory perception” Perception and production develop differently

    28. The End

More Related