Resumo

This is a priming study of two groups of Brazilian Portuguese words, carefully matched for frequency and size, assessed by reaction times (RTs) and event-related brain potentials (ERPs) from 36 college students. The test comprised 360 prime-target pairs, 120 of which were the experimental: a phonological group (PG) of sixty pairs with similar onsets (tarântula-tartaruga ‘tarantula-‘turtle’) and a morphological group (MG) with 60 pairs holding a morphological relationship (globo-globalizar ‘globe’-‘globalize’). In PG, the end of the targets coincides with the Saussurean Arbitrariness Point (SAP), where form is mapped to meaning. Contrastingly, in MG targets, SAP is internal. For instance, in globalize SAP is at globe, but globalize contains more layers beyond globe  (glob_al, glob_al_ize) that are not interpreted arbitrarily. They are computed compositionally. In PG, a target as tartaruga  ‘turtle is similar in linear size to globalize, but different internally. The hypothesis was that if the N400 is an index of  SAP, then   tartaruga  would yield a longer-latency N400 than globalize because SAP is at the end of PG words but in the middle of MG words.The EEG signal was recorded continuously and N400s were calculated for all subjects at each derivation. Targets in the PG group were indeed related to longer latency N400s. But different lengths in MG did not yield different N400 latencies. Nevertheless the behavioral findings of the MG; were very similar to those of PG. Results point to the significant conclusion that while RTs relate to the whole word, N400s ERPs specifically detect SAP. These findings pose an interesting question to the assessmet of the neurophysiology of the morphological computations in the brain that wil be the theme of further studies.