Positive affective contagion in bumble bees.

Affective contagion, a core component of empathy, has been widely characterized in social vertebrates but its existence in any invertebrate is unknown. Using a cognitive bias paradigm we demonstrate positive affective contagion in bumble bees. After being trained on colored flowers with different reinforcements, bees that interacted with a conspecific in a positive affective state were quicker and more likely than controls to land on ambiguous colored flowers, indicating the transfer of a positive judgment bias between bees. Additional observations and experiments showed that affect could be transmitted between bees without physical contact, i.e., through visual modality alone. Our findings suggest that affective contagion may be an evolutionarily widespread mechanism present in both social vertebrates and social insects. Editor's summary: Being able to adopt a knowledgeable conspecific's perspective is highly adaptive. Likely for this reason, emotional contagion, or the spread of emotion from one individual to another, is widely distributed among vertebrates. Such an ability, however, would also be adaptive in nonvertebrates, especially those that are social. Whether insect brains are capable of such coordination has been unknown. Romero-González et al. looked at this behavior in bumble bees, whose tiny, but seemingly mighty, brains have already been shown capable of many unexpected cognitive feats. They found that a demonstrator's positive attitude toward the potential for a reward was readily picked up by an observer. —Sacha Vignieri [ABSTRACT FROM AUTHOR]