This time, the tamarins' reactions were measured not in terms of sucking, but according to whether they turned their heads toward the loud speaker. The tamarins who hear a change of language are more likely to turn towards the speaker than if they hear only a change in voice. In general terms, these findings reveal striking similarities between the two species, as well as substantial differences. In particular, it has not been established that the two species use the same linguistic cues for language discrimination. Newborn humans are more sensitive to the rhythmical properties of speech.
Tamarins seem to be more sensitive to the phonetic characteristics.
In conclusion, the differences between monkeys and newborn humans is probably not connected to their ability to process acoustic signals, but to more abstract processing. Language Discrimination by Human Newborns and by Cotton-Top Tamarin Monkeys , Franck Ramus, Marc D.Hauser, Cory Miller, Dylan Morris, Jacques Mehler, Science , April 14, 2000.