Shared attention experiments examine the potential differences in function or behavior when stimuli are experienced alone or in the presence of others, and when simultaneous attention of the participants to the same stimulus or set is involved. Previous work has found enhanced reactions to emotional stimuli in social situations, yet these changes might represent enhanced communicative or motivational purposes. This study examines whether viewing emotional stimuli in the presence of another person influences attention to or memory for the stimulus. Participants passively viewed emotionally-valenced stimuli while completing another task (counting flowers). Each participant performed this task both alone and in a shared attention condition (simultaneously with another person in the same room) while EEG signals were measured. Recognition of the emotional pictures was later measured. A significant shared attention behavioral effect was found in the attention task but not in the recognition task. Compared to event-related potential responses for neutral pictures, we found higher P3b response for task relevant stimuli (flowers), and higher Late Positive Potential (LPP) responses for emotional stimuli. However, no main effect was found for shared attention between presence conditions. To conclude, shared attention may therefore have a more limited effect on cognitive processes than previously suggested. Humans are social animals that often prefer acting together, rather than alone 1,2. Potential differences in function or behavior when experienced alone or in the presence of others are referred to as co-presence effects that can be either generated from the mere presence of another or from a shared experience that occurs in the physical or psychological presence of another person 3-5. When simultaneous attention of the participants to the same stimulus or set is involved, shared experience overlaps with the term shared attention 4,6. Indeed, both shared experience and shared attention have been found to affect cognitive function and behavior, such as attention to a target stimuli 3,7 , social learning 8 , memory 9,10 , motivation 11 , judgment 12 and inhibitory control 13. Specifically, shared attention has been found to amplify these processes (etc. memories, emotions, and behavioral learning) 4,6. For example, higher manifestation of social learning was found in the shared attention condition compared to an unshared condition 8. Several 5,14,15 studies have examined the effect of shared attention in emotional contexts, but yielded mixed results. For example, Shteynberg and colleagues examined online shared attention effects on reactions to emotional stimuli. In a series of studies, they presented either short clips or pictures to participants and found enhancement of the subjective feelings (self-reported) for emotional stimuli in the online presence of another person. Specifically, scary advertisements led to higher "scariness" scores in the shared attention condition compared to the same stimuli viewed alone. Similar...