Nasality of Infant Vocalizations Determines Gender Bias in Adult Favorability Ratings

Adults rate vocalizing 3-month-old boys as more socially favorable (pleasant, friendly, fun, likeable, cuddly, cute) than girls when they are producing syllabic sounds. Is the preference due to gender bias or to actual sex differences in the acoustical quality of early vocalizations? In Experiment 1, 59 adults rated videotaped segments of 4 vocalizing boys and 4 vocalizing girls who were dressed identically in white gowns, and labelled with a name representing their sex or a name of the opposite sex. Two infants of each sex produced syllabic sounds, and 2 produced vocalic sounds. Adults rated boys producing syllabic sounds more favorably even when the boys were labelled with the names of girls. Therefore, the preference was not due to gender bias. In Experiment 2, 3 groups of adults (N = 50, 49, and 50, respectively) each viewed and rated 1 of 3 different sets of videotaped infants. The videotapes contained segments of 8 infants (4 boys, 4 girls, 2 of each producing syllabic sounds, and 2 producing vocalic sounds); infants appeared dressed in identical white gowns and were identified only by number, not by name or sex. In addition to the social favorability ratings, adults guessed the sex of the infant. Adults rated syllabic boys more favorably even though gender was disguised, and even though their guesses of gender were no better than chance. In Experiment 3, the vocalizations of the infants who were heard in the 3 videotapes were subjected to spectrographic acoustic analysis. The acoustic quality of boys' syllabic sounds differed from that of girls' only on the feature of nasality. As expected, syllabic, as compared with vocalic, sounds of both boys and girls were similarly longer in duration and differed in frequency characteristics, but these differences were related only to sound category and not to sex. The variance in adult social favorability ratings due to sex of infant was explained by the less nasal acoustic quality of the boys' voices. These results have implications for early socialization, because we know that mothers respond more to less nasal vocalizations. These results parallel the less nasal quality of men's voices as compared with women's voices, and suggest continuities from early vocalizations to speech.