Associated Valence Impacts Early Visual Processing of Letter Strings: Evidence from ERPs in a Cross-modal Learning Paradigm

Emotion effects in event-related potentials (ERPs) during reading have been observed at very short latencies of around 100 to 200 ms after word onset. The nature of these effects remains a matter of debate: First, it is possible that they reflect semantic access, which might thus occur much faster than proposed by most reading models. Second, it is possible that associative learning of a word's shape might contribute to the emergence of emotion effects during visual processing. The present study addressed this question by employing an associative learning paradigm on pronounceable letter strings (pseudowords). In a learning session, letter strings were associated with positive, neutral, or negative valence by means of monetary gain, loss, or zero outcome. Crucially, half of the stimuli were learned in the visual modality, while the other half was presented acoustically, allowing for experimental separation of associated valence and physical percept. In a test session one or two days later, acquired letter strings were presented in an old/new decision task while we recorded ERPs. Behavioural data showed an advantage for gain-associated stimuli both during learning and in the delayed old/new task. Early emotion effects in ERPs were limited to visually acquired letter strings, but absent for acoustically acquired letter strings. These results imply that associative learning of a word's visual features might play an important role in the emergence of emotion effects at the stage of perceptual processing.