PROBABILITY AND STRATEGY - AN ERP STUDY O N THE PROCESSING OF SYNTACTIC ANOMALIES

Syntactic ambiguities requiring additional processing usually elicit p ositive going waveforms with onset latencies between 300 and 600 ms in the event-related potential (ERP). It is still unclear to what extent these components can be viewed either (a) as language specific in nat ure or (b) as members of the domain-unspecific P300 family of componen ts. The present study investigates this question by means of probabili ty manipulations applied to German sentences with subject-object ambig uities. Nonpreferred object-subject (OS) word order requires structura l revisions whereas the initially preferred subject-object (SO) word o rder does not. In the present experiment, the proportions of OS and SO structures were varied across experimental blocks (i.e., .25/.75 vs. .75/.25). The data of 20 participants reveal that ERP components were predominantly influenced when the subjects were explicitly informed ab out the actual proportions before each single block. In this case an e arly frontal positive component at about 400 ms and a subsequent poste rior positivity were elicited by rare sentence structures irrespective of word order, suggesting that sentence processing was under strategi c control. Conversely, participants that were not informed about sente nce proportions showed larger positivities to the unpreferred OS sente nces. Probability manipulations did not affect this pattern significan tly. The data suggest that positivities evoked by syntactic ambiguitie s respond differently to probability manipulations than the P300 compo nent.