Infants’ recognition of fully specified and partially masked words An ecological view on general mechanisms of early lan

1. Infants’ recognition of fully specified and partially masked wordsAn ecological view on general mechanisms of early language acquisition Lacerda, F.,* Klintfors, E.,* Marklund, E.,* Ekman-Brandt, S †., Eklund, M., † Molde, C., † Sjöberg, M., † Sundberg, U.* * Department of Linguistics, Stockholm University, Stockholm, Sweden †Department of Clinical Science, Logopedics and Phoniatrics at Karolinska University Hospital, Huddinge, Sweden ISCA Workshop on Plasticity in Speech Perception, June 15-17, London, UK 2005,

2. Abstract Fifteen Swedish infants (mean age= 13.7 m; range 11 to 16 m) were tested in their ability to recognize whole versus truncated (by brown noise masking) target words referring to toys displayed on a video screen. The target words occurred in final position in short natural utterances. The infants’ responses were measured by the looking time towards the target object relative to the looking time towards the competing non-target objects.The results show that whole target words elicited quick and long gazes towards the target pictures while for the truncated words there was only a weak response, about 1 sec after the truncated word presentation, suggesting that infants may not be able to derive lexical information from partial words in multiple choices tasks until after 1½ years of age. ISCA Workshop on Plasticity in Speech Perception, June 15-17, London, UK 2005,

3. Background Infants may encode words in phonetic detail already at the age of 19 months (Swingley 2003) and even process words incremently in the speech stream at 24 months of age (Swingley, Pinto, Fernald 1999). The present study investigated whether the ability to recognize whole words and partially masked words could be observed in 11 to 16 month-old infants. ISCA Workshop on Plasticity in Speech Perception, June 15-17, London, UK 2005,

4. Method • Subjects Fifteen Swedish infants between 11 and 16 mo. of age (mean age 13.7 mo, sd=1.4) • Visual stimuli (baseline and test) Four pictures (see fig. 1) – the car /bi:len/, the watch /klɔk:an/, the teddy-bear /nal:en/, and the ball /bɔl:en/ – displaying common toys named by highly frequent disyllabic Swedish words (SECDI, Swedish CDI) • Auditory stimuli (test) “Var är ____?” (Where is ____?) Two utterances with whole target words in final position:(the watch and the teddy-bear)Two utterances with target words masked by brown noise either after the first or the second phoneme:bi(len) bo(len) and b(ilen) and b(ollen). ISCA Workshop on Plasticity in Speech Perception, June 15-17, London, UK 2005,

5. Bilen Klockan Bollen Nallen Pictures from Peabody Picture Vocabulary Test and picture booksColor enhancement by the authors ISCA Workshop on Plasticity in Speech Perception, June 15-17, London, UK 2005,

6. Procedure The infants were exposed to pictures showing objects along with auditory stimuli: • All four toys were shown while a lullaby was played (baseline) • Each of the objects was displayed on a full screen while a recorded female speaker presented the target words (exposure):’Here’s the ____’, ’Look at ____’ • All four toys reappeared on the screen while the speaker asked for the target word in questions like:’Where’s the ____?’ The total length of the film was 1 min. 42 sec. The size of the screen was 17”. ISCA Workshop on Plasticity in Speech Perception, June 15-17, London, UK 2005,

7. Analysis The infants’ eye movements were automatically registered by the non-invasive Tobii eye-tracking system and Clear View analysing program (www.tobii.se) that uses low intensity infra-red light emitted by a frame mounted on the screen to derive the subject’s gaze vector. The system provides data with a maximal spatial resolution of 0.5 degrees and 20 ms time resolution. The data is automatically registered as a time sequence of screen gaze coordinates and was subsequently analysed using Mathematica and SPSS. ISCA Workshop on Plasticity in Speech Perception, June 15-17, London, UK 2005,

8. Analysis (cont.) The screen was divided i four quadrants with the object in the center. Gazes within a radius of 10 cm from the center of the quadrant were considered to refer to the object displayed on that quadrant. Eye-movements within a 2000 ms time window, starting 350 ms after the onset of the target word were considered. The total fixation-time for each of the objects during the baseline was used as measure of visual bias. Gains from the baseline to the test-phase were computed for the different target words. ISCA Workshop on Plasticity in Speech Perception, June 15-17, London, UK 2005,

9. Results • Results of t-test analysis showed Object t-value df Sign. (two-tailed) Teddy-bear 2.05 14 5.9% Watch 2.48 13 2.7% Bo+NOISE -0.01 13 99.1% B+NOISE 1.81 13 9.3% ISCA Workshop on Plasticity in Speech Perception, June 15-17, London, UK 2005,

10. Looking time at the objects during baseline (17 sec) The watch The car The teddy-bear The ball Figur 2.The figure shows the confidence intervals for the fixation times for each of the four objects at baseline. The Y-axis – time in milliseconds. ISCA Workshop on Plasticity in Speech Perception, June 15-17, London, UK 2005,

11. Gains for target word ’The watch’ The watch The car The teddy-bear The ball Figure 3. Confidence infervals for gains in fixation times.Target word – ’The watch’. Y-axis – time in milliseconds. ISCA Workshop on Plasticity in Speech Perception, June 15-17, London, UK 2005,

12. Gains for the truncated and masked version of ’bollen’, ’the ball’ The watch The car The teddy-bear The ball Figur 4. Confidence intervals for gain values of the fixation times.Target word ’bollen’ (The ball) with brown noise masking the word after its the second phoneme bo+NOISE. Y-axis – time in milliseconds. ISCA Workshop on Plasticity in Speech Perception, June 15-17, London, UK 2005,

13. Results cont. • Baseline looking times were not significantly different for any of the objects. The teddy-bear had the longest looking time, the ball the shortest while the car and the watch had intermediate looking times. • For the truncated target word ’bilen’, the car, in the version of b+NOISE there was a slight tendency for gazes towards the target object (p<0.093). • None of the infants looked at the ball when the word was produced, but 40% of the infants fixated the object after about 1 sec. This could be interpreted as a positive response, but a late one. ISCA Workshop on Plasticity in Speech Perception, June 15-17, London, UK 2005,

14. Results cont. • A significant response was noted for the non-truncated target word ’The watch’, ’klockan’. • Most of the infants were looking at the car when the target word was produced, but changed 350 ms after initial production of the target word. ISCA Workshop on Plasticity in Speech Perception, June 15-17, London, UK 2005,

15. Discussion • The infants, between 11 and 16 months seemed able to identify the target words when presented intact, with full phonetic information. • However, the infants did not seem to be able to identify the truncated words – except for ”the car”, that they looked at for any initial b-presentation. ISCA Workshop on Plasticity in Speech Perception, June 15-17, London, UK 2005,

16. Bibliography Acknowledgement Work supported by grants from The Swedish Research Council and The Bank of Sweden Tercentenary Foundation. Fernald A., Pinto J. P., Swingley, D., Wineberg, A., McRoberts, G. W. “Rapid games in speed of verbal processing by infants in second year.” Psychological Science 9 228-231, 1998. Fernald A., Swingley D., and Pinto J. P. “When half a word is enough: infants can recognize spoken words using partial phonetic information.” Child Dev. 72 1003-1015, 2001. Lacerda, F. and Sundberg, U. (2004). "An ecological theory of language learning," J Acoust Soc Am. 116, 2523. Lacerda, F., Klintfors, E., Gustavsson, L., Lagerkvist, L., Marklund, E., & Sundberg, U. (2004). Ecological Theory of Language Acquisition. In Genova: Epirob 2004. Swedish Early Communicative Development Inventories (SECDI), Owner and manager: Ph. D. Eva Berglund, Stockholm University. Swingley, D. (2003). Phonetic detail in the developing lexicon. Lang Speech, 46, 265-294. Swingley, D., Pinto, J. P., & Fernald, A. (1999). Continuous processing in word recognition at 24 months. Cognition, 71, 73-108.  ISCA Workshop on Plasticity in Speech Perception, June 15-17, London, UK 2005,