Published online by Cambridge University Press: 17 February 2009
The purpose of this study was to determine (1) whether mothers simplify their speech during the second half of the first year of development when infants begin to comprehend words and use gestures to communicate intentionally, and (2) whether individual differences in mothers' speech adjustments influence their infants' later language acquisition. The subjects for the study were 14 mother-infant pairs from a medically low risk sample who were followed longitudinally. Mothers' mean length of utterance (MLU) was calculated from transcripts of face-to-face interaction when the infants were 0;3, 0;6, and 0;9 in age. Mothers who provided responsive and stimulating environments, as indicated by HOME scores, also reduced their MLU over the age range studied. Moreover, mothers' MLU adjustments during the first year were more predictive than the HOME scale in forecasting receptive language development at 1; 6. In contrast, expressive language abilities at 1; 6 were unrelated to the environmental variables measured but were predicted by child characteristics such as the infant's sex. These results suggest that a mother's ability to ‘fine-tune’ her early linguistic input may be predictive of her child's later receptive language functioning. Precursors of fine-tuning, such as maternal beliefs in reciprocity and infant object orientation, are discussed.
Data collection for this research was supported in part by a March of Dimes Social and Behavioral Sciences Research Grant awarded to Ann Murray while she was at the Boys Town National Institute for Communication Disorders in Children (BTNI) in Omaha, Nebraska. Additional support was provided by a Program Project Grant, and a Biomedicai Research Support Grant, both awarded to BTNI by NINCDS. Data analyses were completed while the first and second authors were postdoctoral fellows (NICHHD # 07255 and DE # 6008300899 respectively) at the Child Language Program of the University of Kansas. Special thanks go to Diane Leader and Peggy Rowley for data collection on the home visits.