DeCaspar, A.J. & Fifer, W.P. Of human bonding: newborns prefer their mothers' voice. Science 208, 1174-1176

Abstract

By sucking on a nonnutritive nipple in different ways, a newborn human could produce either its mother's voice or the voice of another female. Infants learned how to produce the mother's voice and produced it more often than the other voice. The neonate's preference for the maternal voice suggests that the period shortly after birth may be important for initiating infant bonding to the mother.

Full text

Of Human Bonding: Newborns Prefer their Mothers' Voices
Author(s): Anthony J. DeCasper and William P. Fifer
Source:
Science,
New Series, Vol. 208, No. 4448 (Jun. 6, 1980), pp. 1174-1176
Published by: American Association for the Advancement of Science
Stable URL: http://www.jstor.org/stable/1683733
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50-
20 100 1000 20 100 1000
Frequency
(Hz)
Fig. 2. Root mean
square
values at peaks
from spectrum
analyses
for different
types of internal
sound:
0, gurgle;
*, swallow;
A, blowing;
A, chewing
cud; l, rushing
noise; *, quiet
ewe; x,
intestinal
noise; +, eating hay; 0, drinking;
*, eating
nuts.
50-
20 100 1000 20 100 1000
Frequency
(Hz)
Fig. 2. Root mean
square
values at peaks
from spectrum
analyses
for different
types of internal
sound:
0, gurgle;
*, swallow;
A, blowing;
A, chewing
cud; l, rushing
noise; *, quiet
ewe; x,
intestinal
noise; +, eating hay; 0, drinking;
*, eating
nuts.
it was reduced below and above this fre-
quency and at higher frequencies re-
mained at about 20 dB up to the highest
recorded, 5 kHz. The amount of attenua-
tion fluctuated, however: conversation
at normal levels outside the animal could
often, but not always, be understood
when transmitted from inside. Raised
voices were almost always distinct.
Sounds generated within the ewe her-
self were picked up by the implanted hy-
drophone, amplified, and recorded by a
tape recorder or fed directly to the spec-
trum analyzer (as the amplifier had two
outputs we were able to listen while ana-
lyzing the sounds). In the main, sounds
heard were characteristic and identi-
fiable: drinking, eating, swallowing, ru-
mination, and sometimes heavy breath-
ing could be heard. Rumination, unex-
pectedly, was rather quiet. A rushing
sound sometimes accompanied move-
ment by the ewe and irregular gurgles,
probably of digestive origin, occurred
frequently. Periods of quiet were not un-
usual. Figure 2 shows root mean square
values at peaks taken from spectrum
analyses, for different types of internal
sound. These were of low frequency,
tailing off above 500 Hz.
Although we found attenuation of ex-
ternal sounds to be less than in other spe-
cies (2, 3, 6), the loudness peaks and fre-
quency of internal sounds were similar to
those recorded by others (3, 6). How-
ever, average sound levels were lower
than those previously reported (2, 3, 6,
7), especially as we often observed peri-
ods of quiet. In one particular our results
were at variance with those of other
workers: we were not able to hear
sounds from the maternal cardiovascular
system. By holding a hydrophone firmly
against the ewe's skin in the brachial
area we were able to pick up heart
it was reduced below and above this fre-
quency and at higher frequencies re-
mained at about 20 dB up to the highest
recorded, 5 kHz. The amount of attenua-
tion fluctuated, however: conversation
at normal levels outside the animal could
often, but not always, be understood
when transmitted from inside. Raised
voices were almost always distinct.
Sounds generated within the ewe her-
self were picked up by the implanted hy-
drophone, amplified, and recorded by a
tape recorder or fed directly to the spec-
trum analyzer (as the amplifier had two
outputs we were able to listen while ana-
lyzing the sounds). In the main, sounds
heard were characteristic and identi-
fiable: drinking, eating, swallowing, ru-
mination, and sometimes heavy breath-
ing could be heard. Rumination, unex-
pectedly, was rather quiet. A rushing
sound sometimes accompanied move-
ment by the ewe and irregular gurgles,
probably of digestive origin, occurred
frequently. Periods of quiet were not un-
usual. Figure 2 shows root mean square
values at peaks taken from spectrum
analyses, for different types of internal
sound. These were of low frequency,
tailing off above 500 Hz.
Although we found attenuation of ex-
ternal sounds to be less than in other spe-
cies (2, 3, 6), the loudness peaks and fre-
quency of internal sounds were similar to
those recorded by others (3, 6). How-
ever, average sound levels were lower
than those previously reported (2, 3, 6,
7), especially as we often observed peri-
ods of quiet. In one particular our results
were at variance with those of other
workers: we were not able to hear
sounds from the maternal cardiovascular
system. By holding a hydrophone firmly
against the ewe's skin in the brachial
area we were able to pick up heart
sounds from outside the animal without
being able to hear the reported pulsa-
tions from inside. It is possible, and con-
sistent with spectrum analyses, that
these sounds occur at very low frequen-
cies and, when attenuated, are below the
human threshold for sound.
Our results suggest that sounds avail-
able to the sheep fetus, within its normal
fluid environment, are varied and of
rather low frequency when they are gen-
erated by, or within, the mother. Ex-
ternal sounds are attenuated by about 16
to 37 dB, most attenuation occurring at
frequencies around 1 kHz. In the sheep,
external sounds of above 65 dB at the
body wall should often penetrate to the
uterus.
The extent to which sound signals in-
side the amniotic sac are heard by the fe-
tus is another question currently being
explored; in precocial mammals, the
auditory system is believed to become
functional well before birth, and there is
sounds from outside the animal without
being able to hear the reported pulsa-
tions from inside. It is possible, and con-
sistent with spectrum analyses, that
these sounds occur at very low frequen-
cies and, when attenuated, are below the
human threshold for sound.
Our results suggest that sounds avail-
able to the sheep fetus, within its normal
fluid environment, are varied and of
rather low frequency when they are gen-
erated by, or within, the mother. Ex-
ternal sounds are attenuated by about 16
to 37 dB, most attenuation occurring at
frequencies around 1 kHz. In the sheep,
external sounds of above 65 dB at the
body wall should often penetrate to the
uterus.
The extent to which sound signals in-
side the amniotic sac are heard by the fe-
tus is another question currently being
explored; in precocial mammals, the
auditory system is believed to become
functional well before birth, and there is
evidence for this in the sheep after day
100 of gestation (8, 9). A further question
concerns the efficiency of the hearing
mechanism within a totally fluid environ-
ment; the mammalian fetus is known to
move in response to sound from outside
the mother (10), and in the guinea pig,
prenatal exposure to a specific sound
changes the neonate's response to the
sound (11).
Implications for the human fetus are
not clear because of postural, placental,
and other anatomical differences. The
main difference between results of re-
search with the goat (7) and ours can be
attributed to our use of a method of
greater physiological validity, namely,
recording from inside the intact amnion
in the fetus's normal fluid environment.
We suggest that the auditory experience
of the fetal mammal may be considerably
more extensive, more varied, and, as in
birds, possibly of greater postnatal sig-
nificance than has been believed.
SALLY
E. ARMITAGE
B. A. BALDWIN
MARGARET A. VINCE
Institute of Animal Physiology,
Cambridge CB2 4AT, England
References
1. B. Tschanz, Z. Tierpsychol. 4, 1 (1968).
2. J. Bench, J. Gen. Psychol. 113, 85 (1968).
3. J. C. Grimwade, D. W. Walker, C. Wood, Aust.
J. Ment. Retard. 2, 63 (1970).
4. H. Murooka, Y. Koie, N. Suda, J. Gynecol. Ob-
stet. Biol. Reprod. 5, 367 (1976).
5. L. Salk, Trans. N. Y. Acad. Sci. 24, 753 (1962).
6. D. Walker, J. Grimwade, C. Wood, Am. J. Ob-
stet. Gynecol. 109, 91 (1971).
7. R. J. Bench, J. H. Anderson, M. Hoare, J.
Acoust. Soc. Am. 47, 1602 (1970).
8. C. G. Bernhard, I. H. Kaiser, G. M. Kolmodin,
Acta Physiol. Scand. 47, 333 (1959).
9. G. Gottlieb., in The Biopsychology of Develop-
ment, E. Tobach, L. R. Aronson, E. Shaw, Eds.
(Academic Press, New York, 1971), pp. 67-128.
10. E. W. Rubel, in Handbook of Sensory Physiolo-
gy, M. Jacobson, Ed. (Springer, Berlin, 1978),
vol. 9, pp. 133-237.
11. M. A. Vince, Anim. Behav. 27, 908 (1979).
13 November 1979; revised 11 March 1980
evidence for this in the sheep after day
100 of gestation (8, 9). A further question
concerns the efficiency of the hearing
mechanism within a totally fluid environ-
ment; the mammalian fetus is known to
move in response to sound from outside
the mother (10), and in the guinea pig,
prenatal exposure to a specific sound
changes the neonate's response to the
sound (11).
Implications for the human fetus are
not clear because of postural, placental,
and other anatomical differences. The
main difference between results of re-
search with the goat (7) and ours can be
attributed to our use of a method of
greater physiological validity, namely,
recording from inside the intact amnion
in the fetus's normal fluid environment.
We suggest that the auditory experience
of the fetal mammal may be considerably
more extensive, more varied, and, as in
birds, possibly of greater postnatal sig-
nificance than has been believed.
SALLY
E. ARMITAGE
B. A. BALDWIN
MARGARET A. VINCE
Institute of Animal Physiology,
Cambridge CB2 4AT, England
References
1. B. Tschanz, Z. Tierpsychol. 4, 1 (1968).
2. J. Bench, J. Gen. Psychol. 113, 85 (1968).
3. J. C. Grimwade, D. W. Walker, C. Wood, Aust.
J. Ment. Retard. 2, 63 (1970).
4. H. Murooka, Y. Koie, N. Suda, J. Gynecol. Ob-
stet. Biol. Reprod. 5, 367 (1976).
5. L. Salk, Trans. N. Y. Acad. Sci. 24, 753 (1962).
6. D. Walker, J. Grimwade, C. Wood, Am. J. Ob-
stet. Gynecol. 109, 91 (1971).
7. R. J. Bench, J. H. Anderson, M. Hoare, J.
Acoust. Soc. Am. 47, 1602 (1970).
8. C. G. Bernhard, I. H. Kaiser, G. M. Kolmodin,
Acta Physiol. Scand. 47, 333 (1959).
9. G. Gottlieb., in The Biopsychology of Develop-
ment, E. Tobach, L. R. Aronson, E. Shaw, Eds.
(Academic Press, New York, 1971), pp. 67-128.
10. E. W. Rubel, in Handbook of Sensory Physiolo-
gy, M. Jacobson, Ed. (Springer, Berlin, 1978),
vol. 9, pp. 133-237.
11. M. A. Vince, Anim. Behav. 27, 908 (1979).
13 November 1979; revised 11 March 1980
Of Human Bonding: Newborns Prefer Their Mothers' Voices
Abstract. By sucking on a nonnutritive nipple in different ways, a newborn human
could produce either its mother's voice or the voice of anotherfemale. Infants learned
how to produce the mother's voice and produced it more often than the other voice.
The neonate's preference for the maternal voice suggests that the period shortly after
birth may be important for initiating infant bonding to the mother.
Of Human Bonding: Newborns Prefer Their Mothers' Voices
Abstract. By sucking on a nonnutritive nipple in different ways, a newborn human
could produce either its mother's voice or the voice of anotherfemale. Infants learned
how to produce the mother's voice and produced it more often than the other voice.
The neonate's preference for the maternal voice suggests that the period shortly after
birth may be important for initiating infant bonding to the mother.
Human responsiveness to sound be-
gins in the third trimester of life and by
birth reaches sophisticated levels (1), es-
pecially with respect to speech (2). Ear-
ly auditory competency probably sub-
serves a variety of developmental func-
tions such as language acquisition (1, 3)
and mother-infant bonding (4, 5).
Mother-infant bonding would best be
served by (and may even require) the
Human responsiveness to sound be-
gins in the third trimester of life and by
birth reaches sophisticated levels (1), es-
pecially with respect to speech (2). Ear-
ly auditory competency probably sub-
serves a variety of developmental func-
tions such as language acquisition (1, 3)
and mother-infant bonding (4, 5).
Mother-infant bonding would best be
served by (and may even require) the
0036-8075/80/0606-1174$00.50/0 Copyright ? 1980 AAAS
0036-8075/80/0606-1174$00.50/0 Copyright ? 1980 AAAS
ability of a newborn to discriminate its
mother's voice from that of other fe-
males. However, evidence for differ-
ential sensitivity to or discrimination
of the maternal voice is available only for
older infants for whom the bonding pro-
cess is well advanced (6). Therefore, the
role of maternal voice discrimination in
formation of the mother-infant bond is
unclear. If the newborn's sensitivities to
SCIENCE, VOL. 208, 6 JUNE 1980
ability of a newborn to discriminate its
mother's voice from that of other fe-
males. However, evidence for differ-
ential sensitivity to or discrimination
of the maternal voice is available only for
older infants for whom the bonding pro-
cess is well advanced (6). Therefore, the
role of maternal voice discrimination in
formation of the mother-infant bond is
unclear. If the newborn's sensitivities to
SCIENCE, VOL. 208, 6 JUNE 1980
1174 1174

-2 -1
I I 5.8
4.4
4.3
4.5
3.7
3.4
1.0
3.8
3.3
C:
0 +1 +2
I I I
1-U
4.5
Other Mother
Fig. 1. For each subject, signed difference
scores between the median
IBI's without
vo-
cal feedback (baseline) and with differential
vocal feedback
(session 1). Differences of the
four reversal
sessions (*) are based on medi-
ans with differential
feedback in sessions 1
and 2. Positive values indicate a preference
for the maternal voice and negative values a
preference
for the nonmaternal voice. Filled
bars
indicate
that
the mother's
voice followed
IBI's of less than the baseline median;
open
bars
indicate
that her voice followed
intervals
equal to or greater
than the median. Median
IBI's of the baseline (in seconds) are shown
opposite
the bars.
speech subserves bonding, discrimina-
tion of and preference for the maternal
voice should be evident near birth. We
now report that a newborn infant young-
er than 3 days of age can not only dis-
criminate its mother's voice but also will
work to produce her voice in preference
to the voice of another female.
The subjects were ten Caucasian neo-
nates (five male and five female) (7).
Shortly after delivery we tape-recorded
the voices of mothers of infants selected
for testing as they read Dr. Seuss's To
Think That I Saw It On Mulberry Street.
Recordings were edited to provide 25
minutes of uninterrupted prose, and test-
ing of whether infants would differ-
entially produce their mothers' voices
began within 24 hours of recording. Ses-
sions began by coaxing the infant to a
state of quiet alertness (8). The infant
was then placed supine in its basinette,
earphones were secured over its ears,
and a nonnutritive nipple was placed in
its mouth. An assistant held the nipple
loosely in place; she was unaware of the
experimental condition of the individual
infant and could neither hear the tapes
nor be seen by the infant. The nipple was
connected, by way of a pressure trans-
ducer, to the solid-state programming
and recording equipment. The infants
were then allowed 2 minutes to adjust to
the situation. Sucking activity was re-
6 JUNE 1980
+3 +4 corded during the next 5 minutes, but
I..
I=.. voices were never presented. This base-
line period was used to determine the
median interburst
interval (IBI) or time
elapsing
between the end of one burst of
sucking
and the beginning
of the next (9).
A burst was defined as a series of indi-
vidual sucks separated
from one another
by less than 2 seconds. Testing with the
voices began after the baseline had been
established.
For five randomly selected infants,
sucking
burst terminating
IBI's equal to
or greater than the baseline median (t)
produced
only his or her mother's
voice
(IBI r
t), and bursts terminating
inter-
vals less man nce meuian prouuceu onmy
the voice of another
infant's
mother
(10).
Thus, only one of the voices was pre-
sented, stereophonically, with the first
suck of a burst
and remained
on until
the
burst ended, that is, until 2 seconds
elapsed without a suck. For the other
five infants, the conditions were re-
versed. Testing lasted 20 minutes.
A preference for the maternal voice
was indicated if the infant produced it
more often than the nonmaternal
voice.
However, unequal frequencies not in-
dicative of preference for the maternal
voice per se could result either because
short (or long) IBI's were easier to pro-
duce or because the acoustic qualities
of
a particular
voice, such as pitch or in-
tensity, rendered it a more
effective
form
of feedback. The effects of response re-
quirements and voice characteristics
were controlled (i) by requiring
half the
infants to respond after short IBI's to
produce the mother's voice and half to
respond
after
long ones and (ii)
by having
each maternal voice also serve as the
nonmaternal
voice for another
infant.
Preference
for the mother's
voice was
shown by the increase in the proportion
of IBI's capable of producing
her voice;
the median
IBI's shifted from their base-
line values in a direction that produced
the maternal
voice more than half the
time. Eight of the ten medians were
shifted in a direction of the maternal
voice (mean = 1.90 seconds, a 34 per-
cent increase) (sign test, P = .02), one
shifted
in the direction that produced
the
nonmaternal
voice more often, and one
median did not change from its baseline
value (Fig. 1).
If these infants were working
to gain
access to their mother's voice, reversing
the response requirements
should result
in a reversal
of their IBI's. Four infants,
two from each condition, who produced
their mother's voice more often in ses-
sion 1 were able to complete a second
session 24 hours later, in which the re-
sponse requirements
were reversed
(11).
0.
0
4)
0
A" I
0. 0
I I I I I I I I I I
.2t t 2t
Interburst intervals
Fig. 2. Interburst interval per opportunity
when the maternal
voice followed intervals
less than the baseline median
(solid line) and
intervals
equal to or greater
than the median
(dashed line). The IBI's are represented
on
the abscissa by the lower bound of interval
classes equal to one-fifth
the baseline median
(t).
Differential feedback in session 2 began
immediately after the 2-minute adjust-
ment period. The criterion time re-
mained equal to the baseline median of
the first session. For all four infants, the
median IBI's shifted toward the new cri-
terion
values and away from those which
previously
produced
the nmaternal
voice.
The average magnitude of the difference
between the medians of the first and re-
versal sessions was 1.95 seconds.
Apparently
the infant learned to gain
access to the mother's voice. Since spe-
cific temporal
properties
of sucking
were
required to produce the maternal voice,
we sought evidence for the acquisition
of temporally differentiated responding.
Temporal discrimination within each
condition was ascertained
by construct-
ing the function for IBI per opportunity:
IBI's were collected into classes equal
to
one-fifth the baseline median, and the
frequency of each class was divided by
the total frequency of classes having
equal and larger values (12). When IBI's
less than the baseline median were re-
quired, the likelihood of terminating
in-
terburst intervals
was highest
for classes
less than the median (Fig. 2), whereas
when longer intervals were required, the
probability of terminating an IBI was
maximal for intervals
slightly
longer
than
the median. Feedback from the maternal
voice effectively differentiated
the tem-
poral character
of responding
that pro-
duced it: the probability of terminating
IBI's was highest when termination re-
sulted in the maternal voice.
Repeating the experiment with 16 fe-
male neonates and a different discrimina-
tion procedure confirmed their prefer-
ence for the maternal voice (13). The dis-
criminative
stimuli
were a 400-Hz
tone of
4 seconds duration
(tone) and a 4-second
1175

period of silence (no tone). Each IBI
contained an alternating sequence of
tone-no-tone periods, and each stimulus
was equally likely to begin a sequence.
For eight infants, a sucking burst initi-
ated during a tone period turned off the
tone and produced the Dr. Seuss story
read by the infant's mother, whereas
sucking bursts during a no-tone period
produced the nonmaternal voice. The
elicited voice remained until the sucking
burst ended, at which time the tone-no-
tone alternation began anew. The dis-
criminative stimuli were reversed for the
other eight neonates. Testing with the
voices began immediately after the 2-
minute adjustment period and lasted 20
minutes. Each maternal voice also
served as a nonmaternal voice.
During the first third of the testing ses-
sion, the infants were as likely to suck
during a stimulus period correlated with
the maternal voice as during one corre-
lated with the nonmaternal voice (Table
1). However, in the last third of the ses-
sion the infants sucked during stimulus
periods associated with their mother's
voice approximately 24 percent more of-
ten than during those associated with the
nonmaternal voice, a significant increase
[F(l, 14) = 8.97, P < .01]. Thus, at the
beginning of testing there was no in-
dication of stimulus discrimination or
voice preference. By the end of the 20-
minute session, feedback from the ma-
ternal voice produced clear evidence of
an auditory discrimination; the probabili-
ty of sucking during tone and no-tone pe-
riods was greater when sucking pro-
duced the maternal voice.
The infants in these studies lived in a
group nursery; their general care and
night feedings were handled by a number
of female nursery personnel. They were
fed in their mothers' rooms by their
mothers at 9:30 a.m. and at 1:30, 5:00,
and 8:30 p.m. At most, they had 12 hours
of postnatal contact with their mothers
before testing. Similarly reared infants
prefer the human voice to other acousti-
cally complex stimuli (14). But, as our
data show, newborns reared in group
nurseries that allow minimal maternal
contact can also discriminate between
their mothers and other speakers and,
moreover, will work to produce their
mothers' voices in preference to those of
other females. Thus, within the first 3
days of postnatal development, new-
borns prefer the human voice, discrimi-
nate between speakers, and demonstrate
a preference for their mothers' voices
with only limited maternal exposure.
The neonate's capacity to rapidly ac-
quire a stimulus discrimination that con-
1176
Table 1. Mean (X) and standard
deviation
(S.D.) of the relative frequency of sucking
during
a stimulus associated with
the maternal
voice divided by the relative frequency of
sucking during
a stimulus associated
with the
nonmaternal voice. A ratio
of 1.0 indicates no
preference.
Stimulus
associated First third Last third
with
maternal
voice * S.D.
Tone 0.97 .33 1.26 .33
No tone 1.04 .31 1.22 .19
Combined 1.00 .32 1.24 .27
trols behavior (15) could provide the
means by which limited postnatal experi-
ence with the mother results in prefer-
ence for her voice. The early preference
demonstrated here is possible because
newborns have auditory competencies
adequate for discriminating individual
speakers: they are sensitive to rhythmic-
ity (16), intonation (17), frequency varia-
tion (1, 13), and phonetic components of
speech (18). Their general sensory com-
petency may enable other maternal cues,
such as her odor (19) and the manner in
which she handles her infant (20), to
serve as supporting bases for discrimina-
tion and vocal preference. Prenatal (in-
trauterine) auditory experience may also
be a factor. Although the significance
and nature of intrauterine auditory expe-
rience in humans is not known, per-
ceptual preferences and proximity-seek-
ing responses of some infrahuman in-
fants are profoundly affected by auditory
experience before birth (21).
ANTHONY J. DECASPER
WILLIAM P. FIFER
Department of Psychology,
University of North Carolina at
Greensboro, Greensboro 27412
References and Notes
1. R. B. Eisenberg, Auditory Competence in Early
Life: The Roots of Communicative Behavior
(University
Park
Press, Baltimore,
1976.)
2. P. D. Eimas, in Infant Perception: From Sensa-
tion to Cognition, L. B. Cohen and P. Sala-
patek,
Eds. (Academic
Press, New York, 1975),
vol. 2., p. 193.
3. B. Friedlander,
Merrill-Palmer
Q. 16, 7 (1970).
4. R. Bell, in The Effect of the Infant on Its Care-
giver, M. Lewis and L. A. Rosenblum,
Eds.
(Wiley,
New York, 1974),_p.
1;
T. B. Brazelton,
E. Tronick,
L. Abramson,
H. Als, S. Wise,
Ciba
Found. Symp. 33, 137 (1975).
5. M. H. Klaus
and
J. H. Kennel,
Maternal
Infant
Bonding (Mosby, St. Louis, 1976); P. De-
Chateau, Birth Family J. 41, 10 (1977).
6. M. Miles and E. Melvish,
Nature
(London)
252,
123 (1974);' J. Mehler, J. Bertoncini, M.
Bauri6re,
D. Jassik-Gershenfeld,
Perception
7,
491 (1978).
7. The infants were randomly
selected from
those
meeting
the following
criteria:
(i) gestation,
full
term; (ii) delivery, uncomplicated;
(iii) birth
weight, between 2500 and 3850
grams;
and (iv)
APGAR
score, at
'least
eight at I and 5 minutes
after birth. If circumsized,
males were not ob-
served until at least 12 hours afterward.
In-
formed
written consent was obtained
from the
mother,
and
she was invited
to observe
the test-
ing procedure.
Testing sessions began
between
2.5 and 3.5 hours after the 6 a.m. or 12 p.m.
feeding.
All infants
were bottle-fed.
8. P. H. Wolff,
Psychol.
Issues 5, 1 (1966).
The in-
fants were held in front of the experimenter's
face, spoken to, and then presented
with the
nonnutritive
nipple.
Infants
failing
to fixate
visu-
ally on the experimenter's
face or to suck on the
nipple
were returned
to the nursery.
Once be-
gun, a session was terminated
only if the infant
cried or stopped sucking for two consecutive
minutes. The intitial sessions of two infants
were terminated
because they cried for 2 min-
utes. Their data are not reported. Thus,
the results are based on 10 of 12 infants
meeting
the behavioral
criteria for entering
and
remaining
in the study.
9. With quiet and alert newborns, nonnutritive
sucking
typically
occurs as bursts of individual
sucks, each separated by a second or so, while
the bursts
themselves
are separated
by several
seconds or more. Interburst
intervals
tend
to be
unimodally
distributed with modal values dif-
fering
among
infants. [ K. Kaye, in Studies in
Mother-Infant Interaction, H. R. Schaffer, Ed.
(Academic
Press, New York, 1977)].
A suck
was said to occur when the negative
pressure
exerted on the nipple reached 20 mm-Hg.
This
value is almost always exceeded during
non-
nutritive
sucking
by healthy infants,
but
is virtu-
ally never produced by nonsucking mouth
movement.
10. The tape reels revolved continuously,
and one
or the other of the voices was electronically
switched to the earphones
when the response
threshold
was met. Because
the thresholds
were
detected
electronically,
voice onset occurred
at
the moment
the negative pressure reached
20
mm-Hg.
11. Two infants were not tested a second time, be-
cause we could not gain access to the testing
room, which
served
as an auxillary
nursery
and
as an isolation
room.
The sessions
of two infants
who cried were terminated.
Two other infants
were tested a second time, but in their first ses-
sion one had shown
no preference
and
the other
had shown
only a slight preference
for the non-
maternal voice. Their performance
may have
been
affected
by inconsistent
feedback. Because
their peak sucking pressures were near the
threshold of the apparatus,
very similar sucks
would sometimes
produce
feedback
and some-
times not, and sometimes feedback would be
terminated in the midst of a sucking
burst. Con-
sequently, second session performances of
these two infants, which were much like their
initial
performances,
were uninterpretable.
12. D. Anger, J. Exp. Psychol. 52, 145 (1956).
13. Three other infants began testing with the
voices, but their sessions were terminated
be-
cause they cried. Their data are not included.
This study
is part
of a doctoral
thesis submitted
by W.P.F.
14. E. Butterfield
and G. Siperstein,
in Oral
Sensa-
tion and Perception: The Mouth of the Infant, J.
Bosma, Ed. (Thomas,
Springfield,
Ill., 1972).
15. E. R. Siqueland
and L. P Lipsitt,
J. Exp. Child.
Psychol. 3, 356 (1966);
R. E. Kron, in Recent
Advances in Biological Psychiatry, J. Wortis,
Ed. (Plenum,
New York, 1967),
p. 295.
16. W. S. Condon
and L. W. Sander,
Science 183,
99 (1974).
17. R. B. Eisenberg,
D. B. Cousins, N. Rupp,
J.
Aud. Res. 7, 245 (1966); P. A. Morse, J. Exp.
Child. Psychol. 14, 477 (1972).
18. E. C. Butterfield
and G. F. Cairns,
in
Language
Perspectives: Acquisition, Retardation and In-
tervention, R. L. Schiefelbusch and L. L.
Lloyd, Eds. (University
Park
Press, Baltimore,
1974),
p. 75; A. J. DeCasper,
E. C. Butterfield,
G. F. Cairns,
paper presented
at the fourth
bien-
nial
conference on Human
Development,
Nash-
ville, April 1976.
19. A. MacFarlane, Ciba Found. Symp. 33, 103
(1975).
20. P. Burns,
L. W. Sander,
G. Stechler,
H. Julia,
J.
Am. Acad. Child Psychiatry 11, 427 (1972); E.
B. Thoman,
A. F. Korner,
L. Bearon-Williams,
Child Dev. 48, 563 (1977).
21. G. Gottlieb, Development of Species Identifica-
tion in Birds: An Inquiry into the Prenatal De-
terminants of Perception (Univ. of Chicago
Press, Chicago, 1971);
E. H. Hess. Imprinting
(Van Nostrand-Reinhold,
New York, 1973).
22. Supported
by Research Council
grant
920. We
thank the infants,
their mothers,
and the staff
of
Moses Cane
Hospital,
where
this work was per-
formed,
and A. Carstens
for helping
conduct
the
research.
26 February
1980
SCIENCE, VOL. 208