Larger, enriched cages are associated with ‘optimistic’ response biases in captive European starlings (Sturnus vulgaris)

Anxious and depressed humans typically view circumstances more pessimistically than non-depressed individuals. Here, we explore the proposal that such cognitive biases also exist in non-human animals, and could be used as novel measures of animal welfare. Specifically, we test the hypothesis that wild-caught captiveEuropeanstarlings (Sturnus vulgaris) are more optimistic in their interpretation of ambiguous stimuli […]