N400-effects to task-irrelevant environmental sounds: further evidence for obligatory conceptual processing.

We assessed conceptual priming for environmental sounds in two tasks using pairs of a visually presented word (prime) and an environmental sound (probe). In the physical task, participants indicated to which ear the sound was presented. In the semantic task, participants judged whether a word labeled a sound correctly. The physical always preceded the semantic task to exclude semantic carry-over effects. In both tasks prime word color indicated whether a response was required (Go/NoGo-trials). An N400-effect for unrelated vs. related sounds was observed in all four conditions resulting from the combination of both tasks with response requirement. However, the N400-effect was reduced in the physical task and in NoGo-trials. Hence, meaning of environmental sounds may be processed obligatorily. Both automatic and controlled processes mediate the analysis of sound meaning.