The role of the mother's voice in developing mother's ... - FIU Infant Lab

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F. Z. Sai
voice with positive reinforcers such as the sight of the mother. Conversely,
preference for the mother’s face is likely to be rooted in foetal exposure to the
mother’s speech (Decasper and Spence, 1991; Turkewitz, 1988; Richards et al.,
1992). A growing body of evidence has demonstrated the functioning of foetal
sensory systems during gestation, as well the sequential functional development
of sensory systems (for review, see Lecanuet and Schaal, 1996). The auditory
system develops much earlier than the visual system (Gottlieb, 1971), and healthy
full-term human foetuses respond to a wide variety of sounds and vibrations
originating from outside the womb (Birnholz and Benaceraf, 1983; Kisilevsky and
Muir, 1991; Lecanuet et al., 1986; Serafini and Lindsay, 1984). As well, FHR and
movements to vibroacoustic stimulation were reported in foetuses as early as 26
weeks gestation (Kisilevsky et al., 1992). Data from studies on uterus speech
transmission performed with a hydrophone near the foetal head during delivery,
have revealed a significant better transmission of the maternal voice than of the
external voice (Querleu et al., 1988). We also know that the mother’s voice is the
only auditory stimulus that is transmitted internally via body tissues and bones
(Petitjean, 1989); it also involves diaphragmatic movements generating pressure
changes in the fluid medium of the uterus. Also, prenates of mothers who
listened to ‘soap opera’ theme music during pregnancy showed a preference for
the same music during the postnatal period (Hepper, 1988). The longer the
prenatal exposure of human neonates, living in the Osaka airport neighbourhood,
to airplane noises, the better they slept compared to babies whose mothers
had lived in the area of the airport for shorter times during pregnancy (Ando and
Hattori, 1977). The work of DeCasper and Fifer (1980), DeCasper and Spence
(1986), DeCasper and Prescott (1984) reveals a complexity of bonding and
language processing during the prenatal period. Given that the presence of
potential sensory stimulation in the foetal milieu as well the presence of foetal
sensory sensitivity to acoustic (e.g. Lecanuet et al., 1995) and vibroacoustic (e.g.
Kisilevsky, 1995) stimuli, and the continuity of foetal and newborn response to
sound and vibration, it is, therefore, possible that neonates are born with a longterm
memory for the mother’s voice.
However, the question whether the neonates rapidly associate the mother’s
voice–face at birth, or demonstrate a long-term memory effect for the mother’s
voice learned while the foetus was still in the mother’s womb remains
unanswered. Nevertheless, data from one of our studies in which newborn
infants were exposed to both the mother’s voice and face, among others, show
that mother preference was stronger with shorter delays than with longer delays
between last exposure to the mother and preference testing (Sai, 1990), indicating
that learning the mother’s face is very stable and established as a long-term
memory. The mother’s voice–face association seems, therefore, to take place at
least shortly after the infant’s birth.
These findings replicate and extend our previous research suggesting a rapid
learning of the mother’s face at birth. Such learning, however, vanished when a
previous exposure to the mother’s voice–face combinations (Exps 2 and 4) was
made unavailable to neonates from birth through testing. A prior exposure to the
mother’s voice–face combination remains, therefore, a significant predictor of the
mother’s face recognition at least within the first days of birth. We still do not
know precisely what visual features, the newborns associated to the mother’s
voice in order to make their preferential choices. Nevertheless, the results
strongly suggest an intermodal learning at birth, probably facilitated by a longterm
memory for the mother’s voice learned in the confines of the womb. One
interesting direction for future research concerns the amount of exposure to the
Copyright # 2004 John Wiley & Sons, Ltd. Inf. Child Dev. 14: 29–50 (2005)