The effect of induced mood on language processing has been examined in behavioral and event-related potential (ERP) studies. A previous study examined the effects of induced mood on word imagery processing by the N400 and N700 components of the ERP and behavioral performance in an imageability judgment task in which participants decided whether a word easily evoked visual imagery or not (Ogawa and Nittono, 2019). The N400 amplitude was larger (more negative-going) under positive mood than under negative mood, while reaction time and the N700 amplitude were not affected by induced moods. These results were interpreted as evidence that, compared to negative mood, positive mood facilitates semantic memory activation during word imagery processing. However, it remains unclear whether positive mood facilitates the phenomenological experience of imagery. To replicate and extend the previous findings, this study examined the effects of mood on subjective ratings of word imageability and ERP components. Single words with moderate imageability were used to avoid floor or ceiling effects. If a positive mood facilitates word imageability processing, subjective imageability ratings would be higher under positive mood than under negative mood. The N400 amplitude, but not the N700 amplitude, would be larger under positive mood than under negative mood. Contrary to predictions, an experiment with a sufficient sample size (N = 41) did not replicate the previous findings regarding N400 amplitude. Induced moods also did not affect the subjective imageability ratings and the N700 amplitude. These results suggest that the effects of induced mood on language processing may not occur at the level of single-word processing. Rather, moods may change the strength of association between word concepts in semantic memory.
Keywords: Event-related potential; Imageability; Mood; N400; N700; Semantic memory.
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