In his book, The Expression of the Emotions in Man and Animals, Charles Darwin noted that “Even insects express anger, terror, jealousy, and love by their stridulation.” Almost 150 years later, spurred by an interest in the evolutionary roots of emotional (affective) processes and their underlying mechanisms, there has been a sudden upsurge of research into the question of whether insects and other invertebrates may indeed have emotion-like states (1–4). Recent work has focused on negative affect, but on page 1529 of this issue, Perry et al. (5) broaden the scope to consider positive emotions. The authors report decision-making behavior in bumblebees that is analogous to optimism in humans and may reflect positive affect in both humans and other species (6–8). Moreover, the behavior appears to depend on the activity of dopamine, a neurotransmitter involved in the processing of reward in humans.