Assessment of Mouse Judgment Bias through an Olfactory Digging Task

Abstract

Judgment biases (JB) are differences in the way that individuals in positiveand negative affective/emotional states interpret ambiguous information. Thisphenomenon has long been observed in humans, with individuals in positive statesresponding to ambiguity ´optimistically´ and those in negative states instead showing´pessimism´. Researchers aiming to assess animal affect have taken advantage ofthese differential responses, developing tasks to assess judgment bias as an indicatorof affective state. These tasks are becoming increasingly popular across diversespecies and fields of research. However, for laboratory mice, the most widely usedvertebrates in research and a species heavily relied upon to model affective disorders,only one JB task has been successfully validated as sensitive to changes in affectivestate. Here, we provide a detailed description of this novel murine JB task, andevidence of its sensitivity to mouse affect. Though refinements are still necessary,assessment of mouse JB opens the door for answering both practical questionsregarding mouse welfare, and fundamental questions about the impact of affectivestate in translational research.