Automatic semantic activation is no myth: N400 semantic priming effects in the letter search task in the absence of RT effects.

The claim that semantic activation is an au- tomatic process was recently called a myth, on the basis of the finding that if letter search is performed on a prime word, semantic priming effects on response time are eliminated, whereas repetition effects are preserved. The absence of semantic activation, however, cannot be validly inferred from the lack of response time effects, and con- verging evidence is needed. To this end, we examined the event-related potential correlate of priming, the N400 ampli- tude modulation, in a letter-search priming paradigm. Our experiment replicated the response time effects and demonstrated that the N400 amplitude successfully dif- ferentiates cross-case repetition priming, semantic prim- ing, and neutral conditions. The results clearly indicate that the meaning of the prime word was processed and that semantic activation indeed was present in the letter- search task. The notion that semantic activation is an automatic process should not be abandoned prematurely.