FRANCK RAMUS
• No suffering at birth (APGAR score = 10 at 5 min);
Normal medical assessments at birth and at two days;
No seroconversion to rubella or toxoplasmosis;
Mother not affected by viruses, and not addicted to any
drug including alcohol or tobacco;
No family history of deafness or neurological problems;
No Dutch or Japanese spoken at home.
Babies were tested three hours after feeding on average,
when they could be easily woken and kept in a quiet alert
state, and when their sucking reflex was maximal.
In the present experiment, 32 babies were successfully
tested, 18 males and 14 females, with a mean age of 67 22
hours, a mean gestational age of 40 1; 1 weeks and a mean
birth weight of 3530 402 g. Twenty-nine came from mono-
lingual French families, 2 from families where one or several
other languages than French are spoken and 1 from a family
where no French is spoken. The results of 42 additional ba-
bies were rejected for the following reasons: rejection of the
pacifier (1), sleeping or insufficient sucking before the shift
(12), crying or agitation (9), failure to meet the habituation
criterion (9), sleeping or insufficient sucking after the shift
(6), loss of the pacifier after the shift (4) and computer failure
(1).
Results
Figure 1 shows the number of HA sucks per minute for the
2 groups of subjects. To ensure that babies were in compara-
ble conditions during the habituation phase, an ANOVA was
performed on average number of HA sucks over the 5 min-
utes preceding the shift, and showed no significant effect of
group (control or experimental) [F(1,31) = 2.6, p = 0-12],
although there is a trend for babies in the control group to
suck more, and no significant effect of the language heard
in habituation (Dutch or Japanese) [F(1,31) < 1]. In or-
der to assess whether the experimental group reacted more
to the change than the control group, we conducted an anal-
ysis of covariance (ANCOVA), with the average number of
HA sucks during the 2 post-shift minutes as dependent vari-
able, the average number of HA sucks during the 2 pre-shift
minutes as covariate, and the group as independent variable 7.
Here, there is no significant group effect [F(1,29) < 1],
showing that the babies in the experimental group have not
reacted to the language change.
Discussion
This experiment shows that newborns fail to discriminate
between Dutch and Japanese when the stimuli are not de-
graded at all, consisting just of natural sentences. This may
seem inconsistent with Nazzi et al.’s (1998) finding that sim-
ilar French newborns can discriminate between English and
Japanese. Among the few differences between our experi-
ment and that of Nazzi et al., is the fact that their sentences
were low-pass filtered, whereas ours aren’t. While it may
seem that the more information, the easier the discrimina-
tion, previous experiments on adults suggest that it is not
always the case: Irrelevant information may actually impair
Minutes
Control Group —⅛—Experimental group
Figure 1. Exp. 1: Dutch-Japanese discrimination - Natural
speech. Minutes are numbered from the shift, indicated by the
vertical line. Error bars represent ±1 standard error of the mean.
Adapted with permission from Ramus et al. (2000). Copyright 2000
American Association for the Advancement of Science.
the discrimination (Ramus & Mehler, 1999; Ramus, Dupoux,
Zangl, & Mehler, submitted).
Here, the fact that each newborn hears 4 speakers during
the experiment may constitute such irrelevant information.
Indeed, it has been suggested that the adaptation to speaker
variability is a costly process in younger infants, that may
interfere with other speech categorization abilities (Jusczyk,
Pisoni, & Mullenix, 1992). It is actually remarkable that
all language discrimination experiments performed on new-
borns to this day have used stimuli where speaker variabil-
ity was completely absent, through the use of a single bilin-
gual speaker (Mehler et al., 1988; Moon et al., 1993), or at
least strongly attenuated through the use of low-pass filter-
ing (Mehler et al., 1988; Nazzi et al., 1998). Experiment 1 is
thus the first language discrimination experiment to expose
newborns to 4 different voices.
Speech resynthesis is a convenient technique to test
whether newborns were disturbed by speaker variability:
whatever the original number of speakers, all sentences are
synthesized using only one voice, that of the synthesizer. If
our hypothesis is correct, we should then predict that new-
borns will be able to discriminate the two languages once the
sentences are resynthesized.
7 This is the standard analysis of sucking rates since Christophe,
Dupoux, Bertoncini, and Mehler (1994) showed that it is more ap-
propriate than doing a simple ANOVA on a dishabituation index
(e.g., the difference in sucking rates between the 2 minutes after
and the 2 minutes before the shift). Here, we also ran the ANOVAs
and found that they always led to the same conclusions as the AN-
COVAs. We thus only report the results of the latter.