Speech sounds elicited electric brain responses in healthy premature i
nfants born 30-35 weeks after conception, demonstrating that the human
brain is able to discriminate speech sounds even at this early age, w
ell before term, and supporting previous results suggesting that the h
uman fetus may learn to discriminate sounds while still in the womb. W
e presented preterm infants with stimulus sequences consisting of a re
petitive vowel that was occasionally replaced by a different vowel. Th
is infrequent vowel elicited a response resembling the adult mismatch
negativity, which is known to reflect the brain's automatic detection
of stimulus change. The present results constitute the ontogenetically
earliest discriminative response of the human brain ever recorded.