The relation of maternal language to variation in rate and style of language acquisition.

The main thrust of this paper is to question whether in earlier studies the 'motherese hypothesis' has been adequately tested. The present study first explores concurrent relations between maternal and child language at an early age, using the Snyder, Bates & Bretherton (1981) questionnaire to assess vocabulary at 1;1. With a large sample of 45 subjects, videotaped at 1;1 and 1;8, it was possible to analyse earlier talkers separately from later talkers. The results indicate pre-existing differences between the mothers of earlier and later talkers as early as 1;1--some 5 months before other studies have examined the possible facilitative effects of 'motherese'. Secondly, and perhaps more importantly, when the sample was divided according to stylistic preference at 1;8, several associations between maternal language at 1;1 and MLU at 1;8 emerged for the non-expressive group which were non-existent for the expressive group. These results imply that earlier studies may have been looking for the effectiveness of maternal input too late. Moreover, it may continue to be difficult to demonstrate consistent effects of child-directed speech as long as researchers continue to ignore individual differences in style of language acquisition.