WORD, PSEUDOWORD, AND NONWORD PROCESSING - A MULTITASK COMPARISON USING EVENT-RELATED BRAIN POTENTIALS

Event-related brain potentials (ERPs) to words, pseudowords, and nonwo rds were recorded in three different tasks. A letter search task was u sed in Experiment 1. Performance was affected by whether the target le tter occurred in a word, a pseudoword, or a random nonword. ERP result s corroborated the behavioral results, showing small hut reliable ERP differences between the three stimulus types. Words and pseudowords di ffered from nonwords at posterior sites, whereas words differed from p seudowords and nonwords at anterior sites. Since deciding whether the target letter was present or absent co-occurred with stimulus processi ng in Experiment 1, a delayed letter search task was used in Experimen t 2. ERPs to words and pseudowords were similar and differed from ERPs to nonwords, suggesting a primary role of orthographic and phonologic al processing in the delayed letter search task. To increase semantic processing, a categorization task was used in Experiment 3. Early diff erences between ERPs to words and pseudowords at left posterior and an terior locations suggested a rapid activation of lexico-semantic infor mation. These findings suggest that the use of ERPs in a multiple task design makes it possible to track the time course and the activation of multiple sources of linguistic information when processing words, p seudowords, and nonwords. The task-dependent nature of the effects sug gests that the language system can use multiple sources of linguistic information in flexible and adaptive ways.