In all fairness to Dr. Mehler I have not read the study, and am merely responding to the article in Health Day.
Nonetheless, to quote Dr. Mehler: "Our study shows that prior to any contact with language, the brain of the neonate responds specifically to utterances of language, compared to very similar stimuli [backward speech],"
It is Dr. Mehler whom emphasized the assetion that the neonate had not had any previous contact with language. The significance of this assertion in the conclusions drawn I will leave to Dr. Mehler to explain. If the left-hemisphere typically processes language, then what is the significance between 6 minutes or 6 months of exposure? I do not assert that the bulk of the literature proves the lack of an innate "language endowment". On the other hand I do not think that Dr. Mehler's study is any greater proof that it exists than has been gained by older baby studies.
The assertion that babies are NOT exposed to mother's speach (and others in close proximity) is contrary to decades of study and clinical evidence. There is very substantial peer-reviewed literature on the subject. I would suggest that the assertion contrary to such volume of evidence is more conjectural. See:
Barbara Kisilevsky, Queen's University Anthony DeCasper, University of North Carolina William Fifer, Columbia University DeCasper, A J and Fifer, W P (1980). Of human bonding: newborns prefer their mothers'voices. Science 208, 1174?76 DeCasper A J. and Spence, M J (1986). Prenatal maternal speech influence on newborns'perception of sounds. Infant behaviour and development. 9, 133?150 Moon, C, Cooper, R P and Fifer, W P (1993). Two?day olds prefer their native language.Infant behaviour and development. 16, 495?500 Susan Gregory, University of Birmingham
Lastly, regarding other stimulus in the womb, it is likewise documented. Such as the "shush-shush"ing mentioned previously. The above literature also refers to studies in which the babies responded to recordings of their mother's heartbeats. The rocking response is also widely believed to be effective due to similarity to inner-ear experience of mother's walking. I must say that I have never encountered literature addressing infant response to bowel noises, although it would be logical to assume that exposure to such stimulus also was experienced.