Electrophysiological indices of lexical processing: the effects of verb complexity and age.

To further investigate the effects that argument structure can have on language processing, reaction-time (RT) and event-related potential (ERP) data were collected for 14 younger subjects (M = 23 years) and 13 older subjects (M = 66 years). A cross-modal lexical decision (CMLD) task, involving online processing of high- and low-complexity verbs embedded in sentences, was used. Results of a baseline nonlinguistic visual ERP task indicated that the older group of subjects demonstrated significantly longer P300 latencies and significantly lower P300 amplitudes than the younger subjects. In the sentence task, younger subjects exhibited significantly higher P300 amplitudes when processing high- versus low-complexity verbs, with a similar pattern noted for the older subjects. P300 latencies were significantly shorter for the older group than the younger group. Neither P300 latencies nor RTs were significantly related to verb complexity, although medium to large effect sizes were present. Overall, these findings support earlier notions of argument structure effects.