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One year -old infants follow others' voice direction

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Yi-Cheng Tsai
Yi-Cheng Tsai

1) One-year-old infants can follow the direction of an unseen adult's voice to locate an object, demonstrating their ability to discern voice directionality without visual cues. 2) In a follow-up study, 16-month-olds continued to successfully locate objects based on voice direction even when the speaker was positioned opposite to the target, indicating they were following voice direction rather than just approaching the sound source. 3) While 12-month-olds also performed above chance overall, their ability was less robust, showing emerging but not fully developed skills in following voice direction. In contrast, chimpanzees did not demonstrate an ability to use voice direction to locate objects.

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One- Year- Old infants Follow Others¡¯ Voice Direction Rossano, F., Carpenter, M., & Tomsaello, M. (2012). Journal of Psychological Science, 23(11), 1298-1302. 1
? Joint attention: ¨C the shared focus of two individuals on an object 2
¨C foundational for children¡¯s earliest intersubjective social interactions ? intentional communication ? linguistic communication 3
? Follow the direction of others¡¯ gaze to external targets: ¨C human infants ¨C many nonhuman primates. 4
? No research investigating infants¡¯ (or adults¡¯) ability to follow the direction of someone¡¯s voice to an external entity. 5
? This study investigating: ¨C ability of 1-year-old infants to follow the direction of an adult¡¯s voice to an external target ¨C when they could not see the adult 6
Study 1 ? Investigated whether infants could determine where an unseen adult was looking just by hearing her voice. 7
Method ? Participants: Age N Mean Range 16 months 32 16:0 months 15:15 ~ 16:15 ¨C 12 excluded ? fussy ( n= 7) ? distracted by parents ( n= 1) ? did not move (n= 4) 8
Materials and design ? Materials: ¨C a large wooden barrier (160 cm ¡Á 0.9 cm ¡Á 122 cm) ¨C four pairs of matching cardboard boxes (each 34 cm ¡Á 24 cm ¡Á 17 cm) 9
Materials and design ? Design: ¨C 2 right, 2 left 10
Procedure an experimenter positioned herself behind a tall barrier opened two boxes on the floor at either side of it(one of the boxes contained a toy) behind the barrier verbally expressed excitement while looking (with her head turned) toward one of the two boxes whether infants subsequently went to that box to get the toy 11
Results and discussion ? 1st trial: ¨C 81%, above chance (sign test, p < .001, g = .32) ? Four trial: ¨C still significantly better than chance ¨C mean number of correct trials = 2.56, SD = 0.62; Wilcoxon signed-rank exact test: T+ = 136, N = 161, p < .001; r = .68 12
Results and discussion ? 16-month-olds: ¨C follow another person¡¯s voice direction ¨C can use it to infer what that person is attending to (even if he or she cannot be seen) ? Another explanation: ¨C mouth was not at the center of the barrier ¨C ¡°come here¡± 13
Study 2 ? Study 2 pitted the source-of-sound explanation against the voice-direction explanation. 14
Method ? Participants: Age N Mean Range 12 months 32 12:6 months 12:0 ~ 12:29 16 months 32 16:0 months 15:15 ~ 16:15 ¨C excluded ? fussy (12-month-olds: n = 3, 16-month-olds: n = 2) ? distracted by their parent during the test (12-month-olds: n = 1; 16- month-olds: n = 2) ? did not move (12-month-olds: n = 4; 16-month-olds: n = 7) 15
Procedure ? Same as study 1 except: ¨C the experimenter positioned herself on the side opposite the correct box 16
Results and discussion ? 16 m: ¨C 1st trial: ? 78%, above chance, (sign test, p < .01, g = .28) ¨C Four trial: ? better than chance ? mean number of correct trials = 2.53, SD = 0.70; Wilcoxon signed-rank exact test: T + = 120, N = 15, p < .001; r = .60 17
Results and discussion ? 12 m: ¨C 1st trial: ? 61%, at chance, (sign test, p = .24, g = .11) ¨C Four trial: ? better than chance ? mean number of correct trials = 2.44, SD = 0.77; Wilcoxon signed-rank exact test: T + = 123, N = 16, p < .01; r = .50 18
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Study 3 ? Primate: chimpanzees ? Subjects : 16 chimpanzees(7 m, 9 f) 20
Results ? 1st trial: ¨C 7/16 at chance, (sign test, p = .80) ? 12 trials: ¨C at chance ¨C mean number of correct trials = 6.19, SD = 1.64; Wilcoxon signed-rank exact test: T+ = 38, N = 11, p = .65; r = .11 21
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General discussion ? When the experimenter was out of sight behind the barrier and talked excitedly about the toy. 23
General discussion ? They were able to determine which box the toy was in, even on their very first trial. 24
General discussion ? Study 2 : ¨C not just approaching the source of the sound and chancing upon the toy ¨C rather, they were following the experimenter¡¯s voice direction to the toy ? 12-month-olds: ¨C less robust but it too was above chance level overall 25
General discussion ? 1-year-old infants: ¨C can discern the directionality of a voice without seeing the speaker ¨C appear to be able to use voice direction to infer the speaker¡¯s focus of (visual) attention 26
Joint Attention 27
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One year -old infants follow others' voice direction

  • 1. One- Year- Old infants Follow Others¡¯ Voice Direction Rossano, F., Carpenter, M., & Tomsaello, M. (2012). Journal of Psychological Science, 23(11), 1298-1302. 1
  • 2. ? Joint attention: ¨C the shared focus of two individuals on an object 2
  • 3. ¨C foundational for children¡¯s earliest intersubjective social interactions ? intentional communication ? linguistic communication 3
  • 4. ? Follow the direction of others¡¯ gaze to external targets: ¨C human infants ¨C many nonhuman primates. 4
  • 5. ? No research investigating infants¡¯ (or adults¡¯) ability to follow the direction of someone¡¯s voice to an external entity. 5
  • 6. ? This study investigating: ¨C ability of 1-year-old infants to follow the direction of an adult¡¯s voice to an external target ¨C when they could not see the adult 6
  • 7. Study 1 ? Investigated whether infants could determine where an unseen adult was looking just by hearing her voice. 7
  • 8. Method ? Participants: Age N Mean Range 16 months 32 16:0 months 15:15 ~ 16:15 ¨C 12 excluded ? fussy ( n= 7) ? distracted by parents ( n= 1) ? did not move (n= 4) 8
  • 9. Materials and design ? Materials: ¨C a large wooden barrier (160 cm ¡Á 0.9 cm ¡Á 122 cm) ¨C four pairs of matching cardboard boxes (each 34 cm ¡Á 24 cm ¡Á 17 cm) 9
  • 10. Materials and design ? Design: ¨C 2 right, 2 left 10
  • 11. Procedure an experimenter positioned herself behind a tall barrier opened two boxes on the floor at either side of it(one of the boxes contained a toy) behind the barrier verbally expressed excitement while looking (with her head turned) toward one of the two boxes whether infants subsequently went to that box to get the toy 11
  • 12. Results and discussion ? 1st trial: ¨C 81%, above chance (sign test, p < .001, g = .32) ? Four trial: ¨C still significantly better than chance ¨C mean number of correct trials = 2.56, SD = 0.62; Wilcoxon signed-rank exact test: T+ = 136, N = 161, p < .001; r = .68 12
  • 13. Results and discussion ? 16-month-olds: ¨C follow another person¡¯s voice direction ¨C can use it to infer what that person is attending to (even if he or she cannot be seen) ? Another explanation: ¨C mouth was not at the center of the barrier ¨C ¡°come here¡± 13
  • 14. Study 2 ? Study 2 pitted the source-of-sound explanation against the voice-direction explanation. 14
  • 15. Method ? Participants: Age N Mean Range 12 months 32 12:6 months 12:0 ~ 12:29 16 months 32 16:0 months 15:15 ~ 16:15 ¨C excluded ? fussy (12-month-olds: n = 3, 16-month-olds: n = 2) ? distracted by their parent during the test (12-month-olds: n = 1; 16- month-olds: n = 2) ? did not move (12-month-olds: n = 4; 16-month-olds: n = 7) 15
  • 16. Procedure ? Same as study 1 except: ¨C the experimenter positioned herself on the side opposite the correct box 16
  • 17. Results and discussion ? 16 m: ¨C 1st trial: ? 78%, above chance, (sign test, p < .01, g = .28) ¨C Four trial: ? better than chance ? mean number of correct trials = 2.53, SD = 0.70; Wilcoxon signed-rank exact test: T + = 120, N = 15, p < .001; r = .60 17
  • 18. Results and discussion ? 12 m: ¨C 1st trial: ? 61%, at chance, (sign test, p = .24, g = .11) ¨C Four trial: ? better than chance ? mean number of correct trials = 2.44, SD = 0.77; Wilcoxon signed-rank exact test: T + = 123, N = 16, p < .01; r = .50 18
  • 19. 19
  • 20. Study 3 ? Primate: chimpanzees ? Subjects : 16 chimpanzees(7 m, 9 f) 20
  • 21. Results ? 1st trial: ¨C 7/16 at chance, (sign test, p = .80) ? 12 trials: ¨C at chance ¨C mean number of correct trials = 6.19, SD = 1.64; Wilcoxon signed-rank exact test: T+ = 38, N = 11, p = .65; r = .11 21
  • 22. 22
  • 23. General discussion ? When the experimenter was out of sight behind the barrier and talked excitedly about the toy. 23
  • 24. General discussion ? They were able to determine which box the toy was in, even on their very first trial. 24
  • 25. General discussion ? Study 2 : ¨C not just approaching the source of the sound and chancing upon the toy ¨C rather, they were following the experimenter¡¯s voice direction to the toy ? 12-month-olds: ¨C less robust but it too was above chance level overall 25
  • 26. General discussion ? 1-year-old infants: ¨C can discern the directionality of a voice without seeing the speaker ¨C appear to be able to use voice direction to infer the speaker¡¯s focus of (visual) attention 26
  • 28. 28