Physiological reactions at encoding selectively predict recognition of emotional images.

The study aimed to investigate the link between physiological responses at encoding and subsequent memory of emotional stimuli, differing in two dimensions: valence and arousal. The participants (all male) freely viewed emotional images, while their pupil size and heart rate were recorded. Then, they were presented with a recognition task. Both pupil constriction and heart rate deceleration evoked by an image onset at the encoding predicted its later correct recognition. However, these effects interacted with valence and arousal. Increased pupillary constriction predicted correct recognition particularly well for low-arousing and negatively valenced images. Deeper heart rate deceleration was related to higher rate of correct recognition mainly in the case of negative images. The results show also an interaction between valence and arousal in their effect on memory. Higher arousal was linked to better recognition, but only when images were of neutral or positive valence. In contrast, negative images were remembered accurately, regardless of the level of arousal. This pattern of results supports the primacy of negative information in early memory consolidation. Overall, we demonstrate that physiological reactions at encoding - which can be linked to the depth of stimulus processing during memory formation - predict recognition accuracy. The emotional load of stimuli further modulates the prediction strength.