Universals in infant directed speech Recognizing intentions in infant directed speech Evidence for universals Gregory A Bryant University of California Los Angeles H Clark Barrett University of California Los Angeles 11 2006 in press Psychological Science Acknowledgements This project was made possible by research grants from the UCLA FPR Center for Culture Brain and Development to G A Bryant and H C Barrett Many thanks to the mothers who provided vocal samples Denae Doyle Leah Dunsmoore Rebecca Huth Holly Mackay Sarah Samppala Jessie Sanford Bonnie Traynor and Sandra Wolfanger Thanks also to the UCLA Experimental Biological Anthropology Lab for methodological suggestions and Michael Mitchell for help with the statistical analyses We especially thank the Shuar community of Chinimpi for their participation and continued cooperation with our research Address for correspondence Gregory A Bryant Ph D Center for Culture Brain and Development Department of Psychology University of California Los Angeles 1285 Franz Hall Los Angeles CA 90095 1563 310 825 5326 gabryant ucla edu 1 Universals in infant directed speech 2 Abstract In all languages studied to date distinct prosodic contours characterize different intention categories of infant directed ID speech This vocal behavior likely exists universally as a species typical trait but little research has examined whether listeners can accurately recognize intentions in ID speech using only vocal cues without access to semantic information We recorded native English speaking mothers producing four intention categories of utterances prohibitive approval comfort and attention as both ID and adult directed AD speech and we then presented the utterances to Shuar adults South American hunter horticulturalists Shuar participants were able to reliably distinguish ID from AD speech and were able to reliably recognize the intention categories in both types although performance was significantly better with ID speech This is the first demonstration that adult listeners in an indigenous non industrialized and non literate culture can accurately infer intentions from both ID speech and AD speech in a language they do not speak Universals in infant directed speech 3 Recognizing intentions in infant directed speech Evidence for universals A major function of speech is the communication of intentions When we speak we form our utterances so that others will grasp our meaning In everyday conversation between adult native language users intentions can be conveyed through multiple channels including the syntax and semantics of their language but also through other means such as prosody Accurately communicating intentions to infants however presents a particular challenge Because infants are not yet linguistically competent speakers cannot make use of the full range of language systems normally available between adult language speakers when communicating intentions including using grammar and even the meaning of words themselves Consistent with this view adults often speak differently to infants than they do to adults In particular prosodic cues normally used for conveying intentions in adult directed speech are frequently exaggerated This pattern of exaggerated prosody is called infantdirected ID speech A variety of reasons why adults use ID speech have been proposed Likely functions include eliciting infants attention Fernald Simon 1984 Werker McLeod 1989 and communicating affective intentions Fernald 1989 Fernald 1992 More controversial proposals include that ID speech helps children learn aspects of language such as vowel categories Kuhl et al 1997 Trainor Desjardins 2002 and grammar Morgan Demuth 1996 Fernald 1992 suggested that the function of ID speech changes over developmental time Initially the speech signal might serve to direct infants attention and modulate arousal and affect but by the second year ID speech can fulfill more specific linguistic purposes Universals in infant directed speech 4 Distinctive ID speech has been found in all languages studied to date and it manifests similarly with only subtle variation Falk 2004 Fernald 1992 For instance relative to adult directed AD speech ID speech often has overall higher mean F0 wider F0 range more exaggerated F0 and intensity contours and more musical rhythmic properties than AD speech Fernald 1989 Fernald 1992 described how pitch contours i e F0 values represented over time pattern similarly in relation to communicative intentions across several languages For example prohibitive utterances are often characterized by low F0 narrow F0 range and staccato like bursts In contrast approval vocalizations generally have high average F0 wide F0 range and a prominent F0 rise fall contour These acoustic configurations modulate infants attention and subsequent behavior in expected ways without relying on verbal commands that are not readily understood Along with these apparent production universals there is strong evidence that infants everywhere have a complementary response bias Infants generally prefer to listen to ID speech over AD speech regardless of the gender of the voice e g Werker McLeod 1989 and even prefer ID speech in a foreign language to AD speech in the language they are accustomed to hearing Fernald Morikawa 1993 There is limited evidence that infants respond differentially to distinct types of ID speech Fernald 1993 found that observers coded infants faces as exhibiting more negative affect while listening to ID prohibitives and more positive affect when listening to ID approvals even when the ID speech was in an unfamiliar language Papousek Bornstein Nuzzo Papousek and Symmes 1990 found that infants looked longer at a face while hearing approvals rather than disapprovals These findings suggest that the differential acoustic structure in these ID Universals in infant directed speech 5 speech types modulate infant affect and arousal in predictable ways Some research has examined adults ability to infer intentions of ID and AD speakers Fernald 1989 found that adults were able to correctly identify the communicative intent in content filtered ID speech and AD speech and moreover they were better at this task in the ID speech condition These results support the hypothesis that there is a form function relationship in ID speech that is well suited to facilitate the communication of intentions between ID speakers and preverbal infants Cross cultural work done thus far has only examined ID speech