“Mood can influence our impression of ambiguous stimuli. Perry et al. show that such emotional-state biases are present in bumblebees, a finding that greatly increases the breadth of taxa in which such emotional influences are found.
Specifically, bees that were given a reward of sugar water before a choice between two neutral cues responded as though the cues were positive stimuli. Further, bees given sugar water were more resilient in the face of a simulated predator attack. The application of a dopamine antagonist eliminated these positive predispositions, suggesting that the mechanism is similar to that found in vertebrates.”
“…decision-making behavior in bumblebees that is analogous to optimism in humans and may reflect positive affect in both humans and other species. Moreover, the behavior appears to depend on the activity of dopamine, a neurotransmitter involved in the processing of reward in humans.”