PERCEPTION OF LINGUISTIC RHYTHM BY NEWBORN INFANTS
Figure 6. Exp. 3: Dutch-Japanese discrimination-Sasasa speech
with artificial intonation. Minutes are numbered from the shift, in-
dicated by the vertical line. Error bars represent ±1 standard error
of the mean.
intonation are inseparable: babies may be sensitive to speech
rhythm, but intonation is necessary to fully process it. Yet an-
other interpretation would be that babies can process speech
rhythm, but the stimuli used were inadequate for them to ex-
hibit this ability.
For instance, Ramus et al. (2000) showed that newborns
don’t discriminate Dutch from Japanese anymore when the
same sentences are played backwards. This suggests that
stimuli that are not enough speech-like are not correctly pro-
cessed by babies, even though they contain enough basic
acoustic information for the discrimination to be feasible in
principle. In this respect, sasasa might not be speech-like
enough: there is indeed no natural language with so little
phonetic diversity. It could also be that these stimuli are too
boring or distressing for the babies, as we had hypothesized
regarding a flat intonation. Whatever the appropriate expla-
nation, we will now try to increase the chances that the babies
correctly process the stimuli.
Experiment 4: saltanaj with
artificial intonation
Materials and Method
Stimuli
There are two differences between the stimuli used in Ex-
periment 2 and those of Experiment 3: one is the reduction
of the phonetic inventory (from saltanaj to sasasa), and the
other is the use of artificial intonation contours instead of the
original ones. At least one of them has caused babies to fail
in the discrimination task. It is therefore natural to undo one
of those changes in order to know which was critical. We
thus reverted to the saltanaj stimuli of Exp. 2, but this time
we applied them the artificial intonation contours of Exp. 3.
Participants
Forty babies were successfully tested, 21 males and 19 fe-
males, with a mean age of 68 21 hours, a mean gestational
age of 40; 1 1 weeks and a mean birth weight of 3512 341
g. Twenty-seven came from monolingual French families,
12 from families where one or several other languages than
French are spoken and one from a family where no French is
spoken. The results of 44 additional babies were rejected for
the following reasons: rejection of the pacifier (5), sleeping
or insufficient sucking before the shift (22), crying or agita-
tion (8), failure to meet the habituation criterion (2), sleeping
or insufficient sucking after the shift (4), loss of the pacifier
after the shift (3).
Results
Figure 7 shows the number of HA sucks per minute for
the two groups of babies. There was no significant group
effect on babies’ sucking during the 5 pre-shift minutes
[F(1,39) < 1], neither was there an effect of the habitua-
tion language [F( 1,39) = 2.1, p = 0.16]. An ANCOVA
on the 2 post-shift minutes, controlling for the 2 pre-shift
minutes, shows no significant group effect [F(1,37) = 1.46,
p = 0.24]. However, examination of Figure 7 suggests that
there is an effect, which is confined to the first minute after
the shift. A new ANCOVA, taking as dependent variable the
number of sucks during the first post-shift minute, and con-
trolling for the 2 pre-shift minutes, yields a significant group
effect indeed [F(1,37) = 4.48, p = 0.04]. This suggests that
the newborns have again discriminated between Dutch and
Japanese. However, the effect is weaker than in Experiment
2, being evident during only one minute following the lan-
guage change.
Minutes
Control group —⅛— ExperimentaJ group
Figure 7. Exp. 4: Dutch-Japanese discrimination - Saltanaj
speech with artificial intonation. Minutes are numbered from the
shift, indicated by the vertical line. Error bars represent ±1 standard
error of the mean.
Discussion
We can now come back to the three different interpreta-
tions of Experiment 3 we have proposed. Since no intona-