Language discrimination by human newborns and by cotton-top tamarin monkeys

Science

Volumn 288, Issue 5464, 2000, Pages 349-351

  Ramus, Franck ^a,c   Hauser, Marc D ^b   Miller, Cory ^b   Morris, Dylan ^b   Mehler, Jacques ^a  

^a CNRS   (France)

^b HARVARD UNIVERSITY   (United States)

^c UNIVERSITY COLLEGE LONDON   (United Kingdom)

Author keywords

[No Author keywords available]

Indexed keywords

ANIMAL EXPERIMENT; ARTICLE; AUDITORY SYSTEM; CONTROLLED STUDY; HABITUATION; HUMAN; HUMAN EXPERIMENT; LANGUAGE; MONKEY; NEUROBIOLOGY; NEWBORN; NONHUMAN; NORMAL HUMAN; PRIORITY JOURNAL; SPEECH DISCRIMINATION; SPEECH PERCEPTION;

ANIMALS; CUES; HABITUATION, PSYCHOPHYSIOLOGIC; HUMANS; INFANT, NEWBORN; LANGUAGE DEVELOPMENT; SAGUINUS; SPEECH PERCEPTION;

ANIMALIA; GOSSYPIUM HIRSUTUM; PRIMATES; SAGUINUS IMPERATOR; SAGUINUS OEDIPUS;

EID: 0034646734     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.288.5464.349     Document Type: Article

References (34)

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20. Production of this kind of stimuli is described in detail in [F. Ramus and J. Mehler, J. Acoust. Soc. Am. 105, 512 (1999)]. Supplementary material is available at www.sciencemag.org/feature/data/1047866.shl.
21. The experiment takes place in a sound-attenuated booth with only the baby and the experimenter inside. The experimenter is blind to the experimental condition and listens to masking noise during the test. Newborns are randomly assigned to the control or experimental group. Order of presentation of languages is counterbalanced across subjects. During a given phase, sentences corresponding to the condition are played in random order. The habituation phase lasts at least 5 min. The habituation criterion is a 25% decrease in sucking during two consecutive minutes compared with the maximum number of sucks previously produced in 1 min. Because increases in sucking rate can occur in the absence of stimulation (C. Floccia, thesis, l'Ecole des Hautes Etudes en Sciences Sociales, Paris, 1996), we compared sucking rate increase of the experimental and the control groups. This is done with a covariance analysis, comparing the average number of sucks during the 2 min after the switch (dependent variable) between the two groups and taking account of the average number of sucks during the 2 min before the switch (covariate). This analysis is detailed in [A. Christophe, E. Dupoux, J. Bertoncini, J. Mehler, J. Acoust. Soc. Am. 95, 1570 (1994)] and has been used since.
22. The experiment takes place in a sound-attenuated booth with only the baby and the experimenter inside. The experimenter is blind to the experimental condition and listens to masking noise during the test. Newborns are randomly assigned to the control or experimental group. Order of presentation of languages is counterbalanced across subjects. During a given phase, sentences corresponding to the condition are played in random order. The habituation phase lasts at least 5 min. The habituation criterion is a 25% decrease in sucking during two consecutive minutes compared with the maximum number of sucks previously produced in 1 min. Because increases in sucking rate can occur in the absence of stimulation (C. Floccia, thesis, l'Ecole des Hautes Etudes en Sciences Sociales, Paris, 1996), we compared sucking rate increase of the experimental and the control groups. This is done with a covariance analysis, comparing the average number of sucks during the 2 min after the switch (dependent variable) between the two groups and taking account of the average number of sucks during the 2 min before the switch (covariate). This analysis is detailed in [A. Christophe, E. Dupoux, J. Bertoncini, J. Mehler, J. Acoust. Soc. Am. 95, 1570 (1994)] and has been used since.
23. Subjects are full-term healthy newborns, between 2 and 5 days old, recruited at the Port-Royal maternity hospital in Paris. Forty-two additional babies were tested, and their results were discarded for the following reasons: rejection of the pacifier (1), sleeping or insufficient sucking before the switch (12), crying or agitation (9), failure to meet the habituation criterion (9), sleeping or insufficient sucking after the switch (6), loss of the pacifier after the switch (4), and computer failure (1).
24. (1.31) = 2.6, P = 0.12).
25. In the English-Japanese discrimination experiments by Nazzi et al. (11), the variability due to the four voices was much reduced by low-pass filtering the stimuli. In other experiments (10), a single bilingual speaker was used.
26. P. W. Jusczyk, D. B. Pisoni, J. Mullenix, Cognition 43, 253 (1992).
27. Although the resynthesis process reduces all voices to one, other (prosodic) characteristics of the different speakers are preserved. We did not test discrimination of the natural sentences played backward because of failure of the newborns to discriminate these sentences even when played forward.
28. Twenty additional babies were tested, and their results were discarded for the following reasons: sleeping or insufficient sucking before the switch (6), crying or agitation (4), failure to meet the habituation criterion (1), sleeping or insufficient sucking after the switch (3), and loss of the pacifier after the switch (6).
29. Seven additional babies were tested, and their results were discarded for the following reasons: crying or agitation (1), sleeping or insufficient sucking after the switch (4), and loss of the pacifier after the switch (2).
30. (1.31) = 2.7, P = 0.11).
31. Before these experiments were run, all tamarins had participated in a habituation-dishabituation experiment involving their own species-typical vocalizations. Thus, all subjects were familiar with the general test set-up. Subjects sit in the test cage within the acoustic chamber and do so without stress. They also sit or hang on the front panel during testing, thereby allowing relatively unambiguous observations of head-turning behavior. Experiments were run by transporting a tamarin from the home room to a test room, which was acoustically and visually isolated from all other tamarins. Two observers watched the session from a monitor outside the test room. Stimuli were played back from a concealed speaker only when the subject's head and body were oriented about 180° away from the speaker. A positive response was scored if the subject turned and oriented toward the speaker within the playback period. If the response was ambiguous, we ran the trial again but with a different exemplar from the habituation series. A subject was considered habituated if he or she failed to respond on two consecutive trials. After habituation, the test stimulus was played. The final trial of the session was a post-test playback, presenting the long call of a tamarin. Given the salience of the long call, we expected the tamarins to respond. If they failed to do so, we excluded the entire session, under the assumption that failure to respond to all stimuli represents general habituation to the test setup. The intertrial interval within a session was set at a minimum of 15 and a maximum of 60 s. All trials were videotaped. After a session was run, trials were digitized onto a computer and then scored blind with respect to test condition by stepping through the experiment frame-by-frame. Two observers scored each test trial; interobserver reliability was 0.92.
32. 2 test.
33. The fact that newborns fail under this very condition in experiment 1A is likely due to their immature auditory system, because susceptibility to speaker variability appears to resolve a few months after birth (25).
34. Supported by the Délégation Générale pour l'Armement and a NSF Young Investigator Award to M.D.H. We thank the Port-Royal maternity hospital for providing access to the newborns and we thank the parents for their participation. All parents gave informed consent. We thank the New England Regional Primate Research Center (P51RR00168-37) for providing the tamarins; the research was approved by the Animal Care and Use Committee at Harvard University (92-16) and the CCPPRB Paris-Cochin.