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 mergence 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 string were presented in an old/new decision task while we recorded event-related potentials. 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.