In speech processing, in the first year of life, prosody and phoneme‐relevant aspects
serve different functions. Recent studies have assumed that the two aspects become
integrated at around 9 months of age. The present study investigates the effect of
lexical status on stress processing in a fixed stress language. We hypothesize that
lexicality modulates stress processing, and where the stress cue is in conflict with
the lexical status (legal deviant condition), we will observe differences in age indicating
the stage of integration. We tested 69 6 and 10 month‐old infants in an acoustic oddball
event‐related potential paradigm. A frequent word stimulus (baba) and a pseudoword
(bebe) were used with legal versus illegal stress. We systematically swapped the standard
and deviant roles of the different stress variants in two conditions. In the illegal
deviant condition in the case of the word stimulus, the response pattern typical for
the pseudoword (an MMR to the absence of the stress cue) was missing. This implies
the suppression effect of lexicality. In the legal deviant condition, negative MMR
(N‐MMR) in the second time window indicated a facilitation effect of lexicality in
both age groups. As only the 6‐month‐olds produced an N‐MMR in the first time window,
we concluded that in a fixed stress language, integration starts at 6 months but is
only completed by the age of 10 months. Our results show that lexical status modulates
stress processing at word level in a highly regularly stressed language in which stable,
long‐term language‐specific stress representation exists from early infancy.
