Abstract
BackgroundReliable measurement of affective state in animals is a significant goal of animal welfare. Such measurements would also improve the validity of pre-clinical mental health research which relies on animal models. However, at present, affective states in animals are inaccessible to direct measurement. In humans, changes in cognitive processing can give reliable indications of emotional state. Therefore, similar techniques are increasingly being used to gain proxy measures of affective states in animals. In particular, the ‘cognitive bias’ assay has gained popularity in recent years. Major disadvantages of this technique include length of time taken for animals to acquire the task (typically several weeks), negative experiences associated with task training, and issues of motivation. New methodHere we present a shortened cognitive bias protocol using only positive reinforcers which must actively be responded to. ResultsThe protocol took an average of 4days to complete, and produced similar results to previous, longer methods (minimum 30days). Specifically, rats housed in standard laboratory conditions demonstrated negative cognitive biases when presented with ambiguous stimuli, and took longer to make a decision when faced with an ambiguous stimulus. Comparison with existing methodsCompared to previous methods, this protocol is significantly shorter (average 4days vs. minimum 30days), utilises only positive reinforcers to avoid inducing negative affective states, and requires active responses to all cues, avoiding potential confounds of motivational state. ConclusionsWe have successfully developed a shortened cognitive bias protocol, suitable for use with laboratory rats.
Highlights
Understanding the affective experiences of animals is fundamental for safeguarding animal welfare and enhancing the reliability and reproducibility of scientific studies (Balcombe, 2006)
The current protocol overcomes three main issues identified with animal tests of cognitive bias
Animals are exposed to positive rewards of different sizes rather than positive and negative events; this avoids exposure to negative events during training, which may induce negative affective states and cognitive biases
Summary
Understanding the affective experiences of animals is fundamental for safeguarding animal welfare and enhancing the reliability and reproducibility of scientific studies (Balcombe, 2006). It has been suggested that determining an individual’s interpretation of ambiguous stimuli can give information on their affective state (Mendl et al, 2009) Using this principle, several studies have employed cognitive bias assays to investigate animal responses to ambiguous stimuli in an effort to gain insight into their affective state, commonly before and after an intervention designed to alter affective state. The ‘cognitive bias’ assay has gained popularity in recent years Major disadvantages of this technique include length of time taken for animals to acquire the task (typically several weeks), negative experiences associated with task training, and issues of motivation. Conclusions: We have successfully developed a shortened cognitive bias protocol, suitable for use with laboratory rats
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