Positive mood enhances accessibility of unrelated concepts in the first language but not in the foreign language.

Prior research has shown that, compared to a negative mood, a positive mood facilitates spreading activation within semantic memory in the first language. Yet, little is still known about neurocognitive mechanisms underlying mood effects on semantic processes in the foreign language. Here, we show that a positive mood enhances accessibility of unrelated concepts within semantic memory in the first but not the foreign language. Highly proficient Polish-English bilingual women were induced into positive and negative mood states with animated films and made semantic relatedness judgements about closely related, weakly related, and unrelated prime-target pairs in their first and foreign languages. Mean N400 responses were analysed as neural markers of spreading activation within semantic memory. Our results revealed reduced N400 responses to unrelated word pairs under a positive compared to a negative mood only in the first language. Critically, no mood-driven effects emerged for the foreign language. These findings provide novel evidence that a positive mood broadens spreading activation within semantic memory only in the first language context, making distant concepts more accessible. Critically, they also highlight mood-independent responding when bilinguals operate in their foreign language.