Behaviour 2019
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Unpacking cognitive bias in bumblebees  
Caroline Strang, Felicity Muth. University of Texas at Austin, Austin, Texas, United States

Cognitive bias is frequently used to assess emotion-like states. In these tasks, individuals are trained on an S+/S- discrimination, given a positive or negative experience, and then presented with ambiguous stimuli perceptually between the trained stimuli. A diminished or enhanced response to ambiguous stimuli is described as ‘pessimistic’ or ‘optimistic’, with those terms serving as operationalized definitions of emotion-like states. This paradigm has been used across a broad variety of taxa, including invertebrates, but the mechanism for this type of cognitive bias has not been addressed. Animals have generalization curves around a peak response to a rewarding stimulus. We might expect information from a positive or negative experience to change the shape of the generalization curve and result in changes in responses to ambiguous stimuli. We tested this hypothesis using bumblebees trained to artificial flowers. We found that our experimental manipulation of a positive experience diminished peak shift. These results offer the first mechanistic explanation for cognitive bias by showing that changes to stimulus response curves can underlie ‘optimistic’ and ‘pessimistic’ behaviors.