Pain-Induced Pessimism and Anhedonia: Evidence From a Novel Probability-Based Judgment Bias Test

Judgment bias tests use responses to ambiguous stimuli to infer emotional states in animals. However, with repeated testing, animals can learn to recognize the previously ambiguous stimuli rendering the test less effective. We describe a novel approach to this problem. Calves (n=9) were trained in a spatial discrimination task to associate 5 locations with a specific probability of reward/punishment (Positive: 100%/0%; Near-Positive: 75%/25%;...