INFANT
BEHAVIOR AND DEVELOPMENT
17, 159-l 64 (1994)
Fetal Reactions to Recurrent Maternal
Speech
ANTHONY J. DECASPER
University oj’Nor_th Carolina at Greensboro
JEAN-PIERRE LECANUET
EPHE, CNRS U.R.A. 315
MARIE-CLAIRE BUSNEL
Unil,ersite Paris V
CAROLYN GRANIER-DEFERRE
EPHE, CNRS U.R.A. 315
ROSELYNE MAUGEAIS
Universitc~ Paris V
Pregnant women recited a short child’s rhyme, “the target,” aloud each day between the thirty
third and thirty seventh weeks of their fetuses’ gestation. Then their fetuses were stimulated with
tape recordings of the target and a control rhyme. The target elicited a decrease in fetal heartrate
whereas the control did not. Thus, fetuses’ exposure to specific speech sounds can affect their
subsequent reactions to those sounds. More generally, the result suggests that third trimester
fetuses become familiar with recurrent, maternal speech sounds.
fetal experience
fetal speech perception
fetal memory
fetal-auditory perception
maternal speech
prenatal sensory experience
The hypothesis that normal prenatal exposure
to maternal speech influences the early development of speech perception is consistent with
research
showing
that pregnant
women’s
speech sounds are present in utero, that lateterm fetuses possess relevant perceptual abilities, and that postnatal perception of speech
sounds can be influenced by prenatal experience. One implication of the hypothesis is that
exposure to maternal speech alters fetal perception of speech sounds. A test of this implication
is reported here.
Recordings from within a pregnant human
uterus have revealed the presence of the woman’s speech sounds (Abrams, Gerhardt, &
Peters, 1992; Benzaquen, Gagnon, Hunse, &
supported
by
grant
CIES
This
work
was
34410.360.80604
from the French Ministry of Exterior
Relations to A.J.D.. who was sponsored by P. Roubertoux,
Universite
Paris V, URA 1294 CNRS, Genetique,
Neurogenetique et Comportement. There was also support
from the Fulhright Program and the Research Council of
the University of North Carolina at Greensboro to AJD and
from grant 3006 I, 1300.5 INSERM and 63X CNAMTS to
M.C.B.
and C. Sureau. The authors wish to thank
C. Sureau (Baudelocquc
Maternity CHU Cochin. Paris,
France) and his staff for their valuable help. We are especially grateful to the mothers and their infants for making
this research possible.
Correspondence
to Anthony J. DeCasper, Department
of Psychology. UNC-Greensboro,
Greensboro. NC 27412.
Foreman,
1990; Querleu,
Renard, Versyp,
Paris-Delrue,
& Crepin,
1988; Richards,
Frentzen, Gerhardt, McCann, & Abrams, 1992;
Versyp, 1985). The intensity of her speech in
utero is near its intensity ex utero; some studies
report intrauterine
intensity is slightly augmented and some report it is slightly attenuated. All reports indicate that higher speech frequencies are attenuated more (augmented less)
than lower ones. Otherwise, the spectral properties of maternal speech are similar in and ex
utero. It follows that some acoustical properties
important for speech perception are preserved
in utero. Indeed, adults can readily perceive
suprasegmental features of a pregnant woman’s
speech that had been recorded in utero, for
example, intonation contours or meter, and can
identify about 30% of its individual phonemes
(Querleu et al., 1988; F. Versyp, personal com-
munication, May 5, 1985).
That late-term fetuses respond to sound has
been known for some time (e.g., Busnel &
Granier-Deferre,
1983). Now, studies of stimulus-elicited heartrate change are being used to
assess the character of fetal auditory perception. For example, when fetuses are in a behaviorally active state and are stimulated with
octave-band stimuli centered on 500, 1000, and
2000 Hz at intensities of 10.5, 110, and 120 dB
SPL, ex utero, the stimuli elicit heartrate accel159
160
DeCasper et al.
erations with a probability and magnitude that
increase along with intensity and frequency.
However, if the fetus is in a behaviorally quiescent state, cardiac accelerations are dampened
and the 500 Hz stimulus elicits many more cardiac decelerations at 105 dB and only decelerdtions at 100 dB (M = -10 bpm; Lecanuet,
Granier-Deferre,
& Busnel, 1988). If a quiescent fetus is repeatedly stimulated with the
bisyllable
/hi/w/ which is then changed to
/hahi/, both presented at 95 dB ex utero, cardiac decelerations occur to the initial stimulation and then again at the stimulus change (M =
-2.6
bpm;
Lecanuet,
Granier-Deferre,
&
Busnel, 1989). Quiescent fetuses’ heartrate also
slows with the onset of brief sentences presented at 87 to 90 dB ex utero (M = -3.4 bpm), but
reactions to less intense stimuli have not been
discerned (Lecanuet, Granier-Deferre.
Jacquet,
& Busnel. 1992). Practically speaking. demonstrations of speech discrimination
require that
the fetus be in a behaviorally
quiet state
because that is when heartrate variability
is
low: Detecting the small decelerations elicited
by moderate to low intensity acoustically-complex speech sounds is easier to do when variability is low.
Research with newborns indicates that prenatal experience
with maternal speech can
influence
their perception
of speech cues
important for discriminating
among speakers
(e.g., DeCasper & Fifer, 1980) as well as their
perception
of linguistically-important
speech
sounds (DeCasper & Spence. 1986). In the
DeCasper and Spence (1986) study, pregnant
women
recited
a specific
prose passage
throughout their last 6 weeks of pregnancy.
After birth. their newborns were tested in an
operant choice task where one pattern of sucking was rewarded with a recording of the recited passage and a second pattern was rewarded
with a recording
of a control
passage.
Importantly,
some infants’ test passages had
been recorded by their own mothers whereas
others’ had been recorded by another woman.
The recited passage was the more potent reinforcer. independent of who spoke it during the
test, presumably because of the infants’ prenatal exposure to its acoustic properties.
The data and the hypothesis imply that fetal
perception, too, not just that of young infants,
should be affected by exposure to maternal
speech. This implication was evaluated by hav-
ing pregnant women recite a specific child’s
rhyme, “the target,” each day for a month and
then testing fetal reactions to recordings of the
target rhyme and a control rhyme.
METHOD
Recitation Phase
P~~,~~~nt Suhjrcts. Twenty-eight
healthy
women
in
their thirty fifth week of pregnancy awe recruited Itom the
birth
training
program
at the Cllniquc
Universitaire
Baudelocque.
Paris, France. They volunteered
to participate atier being mformed about the study.
t’roced~wes
und
hfatc~kdr.
Hall’ the women
were
taught to recite a rhyme cntitlcd Ltr Poulerrr and hall’ here
taught a rhyme entitled 1,~ l’clir C‘/u/xrrrt/.’ They wrrc told
to recite their rhyme, the target, aloud three time\ in uccession each day I’M 4 weeks. They recorded the date and
time of each recitation m a log as proof that they followed
instructions.
After 4 week\, their letuses were stimulated
with the recordings of both rhyme\-one
the tarset and the
other the control.
Testing Phase
The mtrautcrine Intenalty of the te\t stimuli was c&ulated to be 5X to 60 dB uhtch approximate\
the level of it
pregnant woman’\ qxech. Although exi\tinp data suggest
that the control stmIuIu\ dclwered at X0 dB would bc too
weak to elicit drtcctahlc cartllac dcccleratwn~ (I.cc;rnuct et
al., IYXY). a large hod!< 01 rewarch indicates that cardiac
reacttonk to the target fiould hc enhanced by prior cxpw
5urc to it (e.g.. Cooptxmith
Xr Leon. IYX4: Demher, IYhO:
Jacohy K: Dallas. lOXI: Jacohy & Wlther?poon.
IYX?_:
Solomon
HL Po~tm;rn, I Y52: Warm-en. IYX3-). Rcwnrch
show\. l’or cxamplc. that Inmiliar stimuli can he detected at
lower inten\itwa
or 5hortcr p~wwntation durations than
unfamiliar
stimuli.
Enhanced perceptual
procc\ring
01
familiar stimuli also wem\ to occur ,ju\t after hirth (e.g..
DeC’a\per Kr Pifcr. 19x1: DeCn\pcr
NC Spcnce. IYXh).
Therefore. the hpecific expectation u:l\ that target \timuli
would elicit a decrcow in letal heartratt‘, hut control \timull
would have no dtxrrnahlr
cflect.
The women uorc earphones (Ku\\ Pro4/AAAI
and II\tcned to continuous melodic guitar music w,how tntcnsity
wa\ gradually incrawl
until It ma\kcd their perccptltrn 01
the speech stimuli hut was not uncomfortable. The masking
music prevented the women 1‘rom influencing MaI reaction\
through their dll’l’ercntlnl wxtion% to the two poa\apr\.
161
Fetal Speech Perception
Beat-to-beat intervals of the fetal heart were recorded,
in ms. with a doppler cardiotocograph
(Hewlett-Packard,
Model 8030) and stored in an Apple Be computer. Cardiac
activity was monitored via the real-time audio and video
displays and a hardcopy tracing (in bpm).
Procedures. The women sat in a comfortable semireclined position and were made to feel at ease while the
transducer was positioned to record fetal heartbeats. The
two or three researchers who were present monitored cardiac activity for indications that the fetus had entered a
quiet state. Behavioral states of 37.week-old fetuses can be
defined by the same systematic covariations among eye
movements, body movements, respiration movements, and
cardiac activity that are used to define behavioral states in
neonates (e.g., Nijhuis, Prechtl, Martin, & Bots, 1982;
Prechtl & O’Brien, 1982). During periods of behavioral
activity, fetal state 2F according to Nijhuis et al. (1982)
there is high variability (HV) in ongoing heartrate (range >
f4 bpm) and there are occasional abrupt movement-induced
accelerations. During quiescent periods, fetal state IF, vatiability in ongoing heartrate is low (range < k3 bpm) and
there are no abrupt movement-induced
accelerations.
Stimuli were presented only when the researchers decided
that fetal heartrate was in a low variability (LV) period.
A maximum of six stimulations were planned. Half the
fetuses were assigned to one stimulus order (TCTCCT) and
half to the reverse order (CTCTTC). Half the fetuses within
each order had been exposed to one of the rhymes and half
to the other. Each stimulation began at the beginning of a
rhyme and lasted 30 s. Successive stimulations were delivered when at least 30 s had elapsed since the end of the last
stimulation, and the fetus was judged to be in a LV period.
Datu Screening. After all fetuses
were tested, three
observers (A.J.D., J.P.L., and R.M.) independently inspected each hardcopy record in its entirety. They partitioned
the entire record into LV periods, HV periods. or neither
(e.g., the hardcopy tracing was unreadable) without regard
to stimulus presentation and without knowledge of the subject’s target or order of stimulation. Heartrate data were
accepted
for analysis
only if all three independent
observers had judged that the fetus was in a LV period during the 15-s prestimulus period and subsequent 30-s stimulus period. If a target (or control) period was eliminated for
any reason, then the paired control (or target) period was
also eliminated. For example, if the record corresponding
to the second control stimulation was rejected, then the
portion corresponding to the second target stimulation was
automatically rejected. These screening procedures maximized the likelihood of analyzing data only from LV periods, minimized the likelihood of biasing the selection of
data, and maintained within-subject equality in the number
and ordinal posttion of target and control stimulations for
statistical purposes. These procedures are similar to those
used in other fetal studies (e.g., Lecanuet, Granier-Deferre,
Cohen, Le HoueTec, & Busnel, 1986; Lecanuet et al., 1987,
1988. 1992).
accepted for analysis. According to the logs, the
17 mothers had recited their targets an average
of 78 times over the preceding 26 days.
The number
of acceptable
stimulations
obtained from each of the 17 fetuses varied. Six
fetuses provided data from all three pairs of target/control stimulations, 2 fetuses provided data
from two pairs of stimulation, and 9 fe-tuses
provided data from one pair of stimulations.
Ten of the 17 had encountered the TCTCCT
order, and 6 of them had La Poulette as the target. Seven
fetuses
had encountered
the
CTCTTC order, and 4 of them had La Poulette
as the target. Successive stimulations were separated, on average, by 7.5 s (range = 30-150 s).
The interbeat intervals were passed through
an algorithm which filtered out artifacts and
converted the interbeat intervals within successive l-s periods to bpm. Thus, the data consisted of artifact-free heartrate in bpm for each
second of the 15-s prestimulus period and 30-s
stimulus period.
Prestimulus
Conditions
We first examined the initial prestimulus periods. The mean pre-target heartrates of the 17
fetuses ranged from 124 to 155 bpm (M =
136.5 bpm, SD = 7.75), and the standard deviations ranged from 0.93 to 3.77 bpm (M = 2.20
bpm, SD = 0.79). The mean pre-control
heartrates ranged from 125 to 153 bpm (M =
135.9 bpm, SD = 7.67), and the standard deviations ranged from 0.90 to 3.77 bpm (M = 2.30
bpm, SD = 0.78). The pre-target and pre-control heartrate levels did not differ, t( 16) = 0.9 1,
nor did the standard deviations, t(16) = -0.28.
Pre-target and pre-control heartrate levels were
correlated, r(16) = .94, p < .005, but the standard deviations were not, r( 16) = .34, p > .05.
Importantly, heartrate levels and standard deviations were not correlated during the pre-target
period, r( 16) = .23, p > .05, nor during the precontrol period, r.( 16) = .17, p > .05. Thus, any
systematic difference in reactions to targets and
controls cannot be attributed to differences in
heartrate that existed during baseline.
RESULTS
Stimulus Effects
Data
For each subject, the mean heartrate of the 15-s
prestimulus
period was subtracted from the
mean heartrate of successive 5-s intervals of
the stimulus period. These difference scores
were analyzed with a mixed analysis of variance (ANOVA) program (BMDP2V, version
Eleven fetuses were eliminated from consideration. Two fetuses could not be recorded, 1
mother failed to return her log, and 8 fetuses
were judged to have been in HV periods during
all stimulations.
Data from 17 fetuses were
162
DeCasper
pc90) which provides conventional and adjusted probability
estimates of F statistics for
repeated measures (Hertzog & Rovine, 1985;
Kisilevsky & Muir, 1991). The first betweensubjects factor, acceptable stimulations (2 vs.
4/6), assessed whether fetuses who had the
minimum number of acceptable stimulations
reacted differently from fetuses who had more.
The second, acoustic structure of the target (La
Paulette
vs. Le Petit
Ctupaud),
assessed
whether reactions differed as a function of the
acoustic properties of the targets. The first
within-subjects
factor, seconds of stimulation
(l-5
vs. 6-10 vs. I I-IS
vs. 26-30),
assessed whether difference
scores changed
across the 30-s stimulus period. The second,
prior exposure (target vs. control), assessed
whether reactivity was influenced by maternal
recitation of a rhyme.
Acceptable stimulations had no effect, I;( I,
13) = 0.18, nor did it interact with any other
factor, 17 values of all interaction terms > IS.
Acoustical structure of the target had no effect.
F( I, 13) = 0.43, nor did it interact with any
other factor, 11values of all interaction terms >
.lS. Seconds of stimulation had no effect, F(S,
65) = 1.30, p > .2S. nor did it interact with any
other factor, all interaction /> values > 38. Only
the main effect of prior exposure was statistically reliable: The average difference score
elicited by the targets (M = -1.25 bpm, S1> =
I .70) differed from the average elicited by the
controls (M = 0.54 bpm. SD = I .92), F( I, 13) =
7.20, /I < .02. Prior exposure did not interact
with any other Factor, all interaction /I values >
.lS (see Figure I).? In addition. the target-clicited decrease was reliably below its baseline,
t( 16) = -3.03, p < .()I; Wilcoxon’s T = 23, p <
.OIS, whereas heartrate during control stimulation did not differ from its baseline, t( 16) =
l.s7,/~>.os;T=ss./~>.os.
Some Post-Hoc Considerations
A. Evidence
for some effect of repeated stimulation was sought by analyzing
difference
scores of the 6 fetuses who yielded data from
et al.
-13
-e
--3
3
TIME E’ROM STIMULUS
8
13
ONSET
18
(5
23
SEC
28
INTERVALS)
Figure 1. Average difference scores (5-s M - 15-s
prestimulus M) at consecutive 5-s intervals b innin
15 s before stimulus onset and ending at stimu
7 us o P
set for targets (filled) and controls (open). The vertical
lines represent f one standard error.
all three pairs of target/control
stimulations.
Factors of the repeated measures ANOVA
were stimulation number (1st vs. 2nd vs. 3rd).
prior exposure. and seconds of stimulation.
Here, too, the only statistically reliable effect
was that of prior exposure, F‘( I. 5) = 5.44, 1~<
.07. Other attempts to find some effect of‘ stimulus repetition also failed to do so.
H. Data from IO fetuses who were judged to
have been in a HV period during testing with a
target and its paired control were analyzed.
First, we detcrmincd that pre-target and precontrol heartrates were equivalent, and then we
conducted a repeated measures ANOVA of
their difference scores. There was no effect of
prior exposure. E‘(I, 9) = 1.33, 17 > .OS: The
average difference score occurring with the tarb<yet (M = 0.44 bpm. .SII = I .2X) did not difl’ci
from that occurring with the control (M = -0. I9
bpm. Sl> = 1.36). There was no effect 01‘ seconds of stimulation. F(S. 35) = 2.04. 17 > IS.
Thus, no familiarity effects were observed during HV periods.
C. Reactions during HV and LV periods were
compared after determining that the prestimulus heartratc means did not differ. t(X) = <I .O.
but that the standard deviations did, t(X) =
4.50, 1~ < .0002. Indeed, the prestimulation
variance of HV periods wa\ almost thrco times
that of LV periods which corroborates
the
obcrservers’ judgments of whether a fetus WBS
in a LV or HV period. The mixed ANOVA had
hcartrate
variability
(LV vs. HV) as the
163
Fetal Speech Perception
between-subjects
factor. Only the heartrate
variability x prior exposure interaction was statistically reliable, F( 1, 26) = 5.51, p < .03.
Target-elicited reactions during LV were more
negative than during HV, and control reactions
during LV and HV did not differ.
DISCUSSION
An important implication of the prenatal experience hypothesis was confirmed: Fetal heartrates
decreased in response to stimulation with target
rhymes their mothers had recited during the previous 4 weeks but did not change in response to
stimulation by control rhymes their mothers had
never recited. The different reactions occurred
with important variables held constant or counterbalanced, and the direction and magnitude of
the target-elicited change were consistent with
existing research. Therefore, we conclude that
fetal reactions to the target were influenced by
previous exposure to the target.
replicates
This
result
systematically
DeCasper and Spence’s (1986) finding with
newborns that target stimuli were more potent
reinforcers than control stimuli. In that study,
mothers had recited the target throughout the
last 6 weeks of pregnancy.
Here, mothers
began reciting about 6 weeks before term but
stopped after 4 weeks. Thus, this study extends
our knowledge of the amount and timing of
prenatal speech experience that is sufficient to
influence the fetus’s/infant’s
subsequent perception of speech sounds.
Although neither this study nor that of
DeCasper and Spence (1986) allows determining which acoustic characteristic(s) of the targets were relevant for the familiarity effects,
they do permit deciding which characteristics
were not necessary.
First, familiarity
with
maternal voice cues cannot have been necessary for the target effects because test stimuli
were recorded
by other women.
Second,
because two French targets and three English
targets have been used, any acoustic characteristics specific to either French or English cannot have been necessary for the familiarity
effects. Third, because the five passages serving as targets also served as controls, the
unique acoustic characteristics of any one passage cannot have been necessary for the familiarity effects. Rather, it seems likely that some
set(s) of characteristics
that can acoustically
define any well-spoken passage from any lan-
guage is capable of supporting prenatal familiarity effects like those observed to date. Such
characteristics
might include intonation contours and/or patterns of syllabic beats and/or
patterns of syllables (e.g., Cooper & Aslin,
1990; Femald & Kuhl, 1987; Lecanuet et al.,
1987; Mehler, Bertoncini, Barriere, & JassikGershenfeld,
1978; R.K. Panneton, personal
communication,
November 15, 1985; Querleu
et al., 1988).
Differential reactivity to the target and control was seen during LV periods but not during
HV periods. This interaction between state and
prior experience is reminiscent of the interactive effects of state and stimulus characteristics
(Lecanuet et al., 1988). Here, too, the interaction may indicate that the small heartrate
decrease elicited by a low-intensity
familiar
stimulus was easier to detect during LV periods
than during HV periods.
This study shows that prenatal exposure to
the “mother’s tongue” can enhance fetal reactions to linguistically
important speech sounds
and, thus, could promote language-relevant
perceptual tuning before birth. More analytical
studies of how prenatal exposure to speech and
nonspeech sounds affects subsequent perception will substantially influence our conception
of perceptual development, language development, and language.
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Warren. R.M. ( I YX2). Autlitot:v pw~~q~fion. A mw s!mlusis. NW York: Pergamon.
2 October
1992;
Revised 3 February 1993
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