INFANT BEHAVIOR AND DEVELOPMENT
INFANT BEHAVIOR AND DEVELOPMENT 9, 1X3-150 (1986)
Prenatal Maternal Speech Influences Newborns’ Perception of Speech Sounds*.
ANTHONY J. DECASPER AND MELANIE J. SPENCE University of North Carolina at Greensboro
Pregnant women recited a particular speech passage aloud each day during their last 6 weeks of pregnancy. Their newborns were tested with an operant-choice procedure to determine whether the sounds of the recited passage were more reinforcing than the sounds of a novel passage. The previously recited passage was more reinforcing. The reinforcing value of the two passages did not differ for a matched group of control subjects. Thus, third-trimester fetuses experience their mothers’ speech sounds and that prenatal auditory experience can in- fluence postnatal auditory preferences.
prenatal sensory experience auditory perception newborn perception fetal experience prenatal learning speech perception moternol voice
Human newborns do not act like passive and neutral listeners. They prefer their own mothers’ voices to those of other females, female voices to male voices, and intrauterine heartbeat sounds to male voices, but they do not prefer their fathers’ voices to those of other males (Brazelton, 1978; DeCasper & Fifer, 1980; DeCasper & Prescott, 1984; Fifer, 1980; Panneton & DeCasper, 1984; Wolff, 1963). Why should newborns prefer some sounds over others? One hypothesis is that their auditory preferences are influenced by prenatal ex- perience with their mothers’ speech and heartbeats (DeCasper & Prescott, 1984). Several considerations suggest this hypothesis is plausible.
Third-trimester fetuses hear, or are behaviorally responsive to, sound (e.g., Bernard & Sontag, 1947; Birnholz & Benacerraf, 1983; Grimwade, Walker, Bartlett, Gordon, & Wood, 1971; Johansson, Wedenberg, & Westin, 1964; Sontag & Wallace, 1935). Intrauterine recordings taken near term indi- cate that maternal speech and heartbeats are audible in utero (Querleu & Renard, 1981; Querleu, Renard, & Crepin, 1981; Walker, Grimwade, &Wood, 1971). Nonmaternal speech, for example male speech, is less audible because of attenuation by maternal tissue and/or masking by intrauterine sounds (Querleu & Renard, 1981; Querleu et al., 1981).
* This research was supported by a Research Council Grant from the University of North Carolina at Greensboro and a generous equipment loan by Professor Michael D. Zeiler. We wish to thank the medical and administrative staff of Moses H. Cone Hospital, Greensboro, NC and, especially, the mothers and their infants for making this research possible. Thanks also to G. Gottlieb, R. Harter. R. Hunt, R. Panneton. K. Smith, and, especially, W. Salinger for their helpful comments on drafts of the manuscript. Portions of this paper were presented at the Third Biennial Interna- tional Conference on Infant Studies, March 1982. Austin, TX.
Correspondence and requests for reprints should be addressed to Anthony J. DeCasper, Department of Psychology, University of North Carolina at Greensboro, Greensboro, NC 27412.
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The newborns’ preference for their own mothers’ voices requires that they had some prior experience with her voice, but there is no evidence that the necessary experience occurred after birth. Fifer (1980) failed to find any relation between maternal-voice preference and postnatal age, whether the newborns roomed with their mother or in a nursery, or whether they were breast fed or bottle fed. Since the maternal voice is audible in utero, and since third-trimester fetuses can hear, perhaps the necessary experience occurred before birth. In contrast, newborns show no preference for their own fathers’ voices, even if they had explicit postnatal experience with his voice. Since male voices are not very audible in utero, perhaps the absence of a paternal-voice preference indi- cates the absence of prenatal experience with his voice (DeCasper & Prescott, 1984). The correlations between the presence or absence of specific-voice sounds before birth, and the presence or absence of specific-voice preferences after birth suggest that prenatal auditory experiences influence the earliest voice preferences.
Consider that complex auditory stimuli can function as positive rein- forcers, neutral stimuli, or negative reinforcers of newborn behavior. Known reinforcers include vocal-group singing, solo female singing, prose spoken by a female, synthetic speech sounds, and intrauterine heartbeat sounds (Butter- field & Cairns, 1974; Butterfield & Siperstein, 1972; DeCasper, Butterfield, & Cairns, 1976; DeCasper & Carstens, 1981; DeCasper & Sigafoos, 1983). On the other hand, male speech and instrumental music lack reinforcing value, while white noise and faster-than-normal heartbeat sounds are aversive (Butter- field & Siperstein, 1972; DeCasper & Prescott, 1984; Salk, 1962). The differen- tial reinforcing effectiveness of these sounds seems to covary more with their similarity to sounds that were present in utero than with any general acoustic characteristic(s), which further suggests that prenatal auditory experience in- fluences postnatal auditory perception.
Finally, prenatal auditory experience has been shown to cause postnatal auditory preferences in a variety of infrahuman species (e.g., Gottlieb, 1981; Vince, 1979; Vince, Armitage, Walser, & Reader, 1982).
The hypothesis implies that prenatal experience with maternal speech sounds causes some property of the sounds to be differentially reinforcing after birth. Speech sounds enable at least two kinds of discriminations; some speech cues allow discrimination of language-relevant sounds, per se, or what is said, and some allow discrimination of the speaker or source of the speech sounds (Bricker & Pruzansky, 1976; Studdert-Kennedy, 1982). Thus, the pre- natal experience hypothesis implies that newborns prefer their own mothers’ voices, regardless of what she says, because of prenatal experience with her voice-specific cues. This implication, however, cannot be directly tested for obvious ethical and practical reasons. The hypothesis also implies that new- borns will prefer the acoustic properties of a particular speech passage if their mothers repeatedly recite that passage while they are pregnant.
We directly tested the latter implication in the following way. First, preg- nant women tape-recorded three separate prose passages. Then, they recited
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one of the passages, their target passage, aloud each day during the last 6 weeks of pregnancy. After birth their infants were observed in an operant learning task where recordings of the target passage and a novel passage, one their mothers had recorded but had not recited, were both available as reinforcers. Then their relative reinforcing effectiveness was evaluated. If the prenatal ex- perience with the target passage increases its reinforcing value then: (a) the acoustic properties of the target passage will be more reinforcing than those of a novel passage; (b) the differential reinforcing value of the target passage should be carried by its language-relevant cues and, thus, should not require the presence of the infant’s own mother’s voice cues; and (c) the reinforcing values of the target and novel passages should not differ for control newborns who had never been exposed to either passage.
METHOD
Prenatal Phase
Pregnant Subjects. Thirty-three healthy women approximately 7 Yz months pregnant were recruited from childbirth preparation classes after being informed about the project. All were experiencing uncomplicated pregnancies.
Prenatal Procedures. After becoming familiar with three short children’s stories they tape-recorded all three. Recordings were made in a quiet room on an Akai 4000 stereophonic tape recorder. The tapes would be used as reinforcers in a postnatal learning task. Each woman was then assigned one of the stories as her target story. Assignment was made after all three had been recorded to prevent them from biasing the recording of their target, for example, by ex- aggerated intonation.
The women were instructed to read their target story aloud “two times through each day when you feel that your baby (fetus) is awake” and to “read the story in a quiet place so that your voice is the only sound that your baby can hear.” They maintained a log of their daily recitations and were occasion- ally checked by the researchers.
Story Materials. The stories were The King, the Mice, and the Cheese (Gurney & Gurney, 1965), the first 28 paragraphs of The Cat in the Hat (Seuss, 1957), and a story we called The Dog in the Fog, which was the last 28 para- graphs of The Cut in rhe Hut with salient nouns changed. The three stories were about equally long, they contained 579, 611, and 642 words, respectively. Each could be comfortably recited in about 3 min. Each was also composed from equal size vocabularies of 152, 142, and 154 words, respectively. Salient, high-frequency nouns common to at least two stories were changed. For exam- ple, cat and hat in The Cut became dog and fog in The Dog, and cat and dog from those stories became turtle and zebra in The King. The Cat contained 46 unique words (i.e., words that appeared only in The Cat), which accounted for 22% of the total word count; The Dog contained 57 unique words, which ac- counted for 22% of the total word count; and The King contained 85 unique
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words, which accounted for 44% of the total word count. All three stories con- tained common high-frequency words. For example, a, all, and, did, do, he, I, in, like, not, now, of, said, that, the, to, with, and you occurred at least three times in each. The common high-frequency words accounted for 43% of The Cat, 38% of the The Dog, and 36% of the The King. The remaining words oc- curred at least once in at least two of the stories. The stories also differed in prosodic qualities, such as patterns of syllabic beats. Thus, they differed in the acoustic properties of individual words as well as in…
