Phonological effects on the auditory N400 event-related brain potential.

We report 3 experiments exploring the responsiveness of the auditory N400 event-related potential to the phonological relations between word or non-word targets and preceding prime words. When subjects had to decide whether primes and targets rhymed, non-rhyming words produced greater negativity in the N400 time range than rhyming words. The same effect was obtained when these targets were spoken by another voice than the prime words, suggesting that the effect is determined by phonological factors, and not merely by a physical-acoustic mismatch (Experiment 1). In the rhyming task, the differential N400 for non-rhyming vs. rhyming words was equally pronounced for non-rhyming vs. rhyming non-words (Experiment 2). In a lexical decision task on the same stimuli, a difference between non-rhyming and rhyming targets was obtained for words, but not for non-words (Experiment 3). The results show that the auditory N400 is sensitive to phonological variables. It is further proposed that phonological effects on the auditory N400 are not manifestations unique to phonological processes that demand conscious attention, but may also reflect operations that are performed automatically during auditory word recognition.