The distractor frequency effect: An overt naming ERP study

In the context of a color naming task, the Distractor Frequency effect refers to the phenomenon of longer latencies for low-frequency than for high-frequency distractor words (Burt, 2002). It remains unclear whether this effect has its locus at lexical or post-lexical stages. This would have important implications for models of spoken word production (Miozzo & Caramazza, 2003). Using the ERPs technique we explored the time-course of the Distractor Frequency effect in comparison to the Frequency effect in word reading and the Stroop effect. We monitored two time windows corresponding to two processing stages: 180-250 ms (lexical access), 300-500 ms (phonological encoding). In the reading task, occipito-parietal ERPs at 180-250 ms were modulated as a function of frequency with low-frequency words producing a negative shift relative to high-frequency words (replicating Cuetos et al., 2009). In the color naming task, fronto-central ERPs at 300-500 ms were characterized by a negative shift for low-frequency distractors relative to high-frequency distractors. Replicating previous findings (Liotti et al., 2000), during this same later interval incongruent trials produced a negative shift relative to congruent trials. These results are discussed in relation to lexical and post-lexical accounts of the Distractor Frequency effect.