Authors’ reprint
More at http://www.ehess.fr/centres/lscp/persons/ramus/science.html
This paper was originally published in Science 288, 349-351
Copyright c 2000 by the American Association for the Advancement of Science
Language discrimination by human newborns
and by cotton-top tamarin monkeys
Franck Ramus
Laboratoire de Sciences Cognitives et Psycholinguistique (EHESS/CNRS),
54 Boulevard Raspail, 75006 Paris, France.
Marc D. Hauser, Cory Miller and Dylan Morris Jacques Mehler
Department of Psychology, Harvard University, Cambridge, Laboratoire de Sciences Cognitives et Psycholinguistique
MA, 02138, USA. (EHESS/CNRS), 54 Boulevard Raspail, 75006 Paris,
France.
Humans, but no other animal, make meaningful use of spoken language. What is unclear,
however, is whether this capacity depends on a unique constellation of perceptual and neu-
robiological mechanisms, or whether a subset of such mechanisms are shared with other or-
ganisms. To explore this problem, we conducted parallel experiments on human newborns
and cotton-top tamarin monkeys to assess their ability to discriminate unfamiliar languages.
Using a habituation-dishabituation procedure, we show that human newborns and tamarins can
discriminate sentences from Dutch and Japanese, but not if the sentences are played backwards.
Moreover, the cues for discrimination are not present in backward speech. This suggests that
the human newborns’ tuning to certain properties of speech relies on general processes of the
primate auditory system.
A fundamental question in the study of language evolution
and acquisition is the extent to which humans are innately
endowed with specialized capacities to comprehend and pro-
duce speech. Theoretical arguments have been used to argue
that language acquisition must be based on an innately spec-
ified language faculty (1, 2), but the precise nature and ex-
tent of this "language organ" is mainly an empirical matter,
which notably requires studies of human newborns as well
as non-human animals (3-5). With respect to studies of hu-
mans, we already know that newborns as young as four days
old have the capacity to discriminate phonemes categorically
(6) and perceive well-formed syllables as units (7-9); they
are sensitive to the rhythm of speech, as shown in experi-
ments where newborns distinguish sentences from languages
that have different rhythmic properties, but not from lan-
guages that share the same rhythmic structure (10, 11); how-
ever newborns don’t discriminate languages when speech is
played backwards (10), and neurophysiological studies sug-
gest that both infants and adults process natural speech dif-
ferently from backwards speech (12, 13). All of these stud-
ies indicate that humans are born with capacities that facili-
tate language acquisition, and that seem well attuned to the
properties of speech. Studies of non-human animals, how-
ever, show that some of these capacities may predate our
hominid origins. For example, insects, birds, non-primate
mammals, and primates process their own, species-typical
Correspondence should be addressed to Franck Ramus. E-mail:
[email protected]. Present address: Institute of Cognitive Neuro-
science, 17 Queen Square, London WC1N 3AR, GB.
sounds in a categorical manner, and some of these species
perceive speech categorically (14-18).
Our aim in this paper is to extend the comparative study
of speech perception in three directions. First, we have con-
ducted joint experiments on human newborns and on mon-
keys using the same design and the same material. Second,
whereas most studies of non-human animal speech percep-
tion involve extensive training prior to testing on a gener-
alization task, our experimental approach - the habituation-
dishabituation paradigm - involves no training, and parallels
the method used in studies of infant speech perception. Thus,
conditions are met to appropriately compare the two popula-
tions. Third, most studies of speech processing in animals
involve tests of phonemic perception. Here, we extend the
analysis to sentence perception, thereby setting up a much
broader range of perceptual problems.
Our experiments were run on human newborns and
cotton-top tamarin monkeys (Saguinus oedipus oedipus).
The stimuli consisted of 20 Japanese and 20 Dutch sentences,
uttered by 4 female native speakers of each language. Condi-
tions where the two languages are pitted against one another
were compared with conditions where speakers of the same
language are contrasted. As an additional factor, sentences
within a session were either played forward or backwards.
To more readily control for prosodic features of the signal,
all conditions were rerun using synthesized exemplars of the
original sentences. Synthesized sentences were created with
the MBROLA diphone synthesizer (19) . Phoneme dura-
tion and fundamental frequency were preserved, whereas the
phonetic inventory was narrowed to only one phoneme per
manner of articulation: all fricatives were synthesized as /s/,