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Research Training Scholarships

Emma Harding

“Novel methods for assessing mental states and animal welfare”

In 1998 UFAW awarded Emma Harding the first Animal Welfare Research Training Scholarship. Emma’s aim was to investigate novel methods for assessing the mental states of animals which centred around cognitive bias theory. Cognitive bias is a term originally developed by psychologists to describe the influence of emotional state on perception, memory, judgement and decision making. When feeling anxious or depressed people are more likely to interpret ambiguous information negatively (i.e. the glass is half empty). Cognitive bias had the potential to offer another means of understanding an animal’s emotional state.

Under the supervision of Mike Mendl, Elizabeth Paul, and Christine Nicol, at the University of Bristol, a new method of using cognitive bias to assess the affective state of rats was pioneered. Rats were trained to press a lever when they heard a tone associated with a positive event (delivery of a 45mg food pellet) and to not press the lever when they heard another tone indicative of a negative event (30 seconds of loud white noise). Once trained, rats were then allocated to either ‘unpredictable’ or ‘predictable’ housing. Unpredictable housing involved between 0 and 2 negative events happening at random times of day such as tilting the cage, introducing a stranger, reversal of the light/dark cycle and damp bedding. ‘Unpredictable’ housing has been found to induce symptoms of a mild depression-like state.

Rats were then exposed to tones with frequencies intermediate between those of the food delivery and noise-avoidance tones. Emma measured the proportion of tones responded to by lever pressing, and the time take to respond to the tones. Overall, rats in unpredictable housing were slower to respond and showed fewer responses to ambiguous tones and to the positive food tone indicating a reduced expectancy of a positive event. This compares with findings for depressed or anxious humans who also have reduced expectations of positive events and interpret ambiguous stimuli negatively.



Mean (±1 s.e.) responses to tones during 10 daily 30-min test sessions for male Lister hooded rats housed under 'predictable' (open circles, n = 4) and 'unpredictable' (filled circles, n = 5) conditions.


a, Proportion of tones to which the animals responded to by pressing a lever.


b, Latent time between sounding of the tone and pressing of the lever. 



Emma published the findings from her work in Nature (along with co-authors Mike Mendl and Elizabeth Paul) and since this time a great many cognitive bias research projects have been carried out to investigate the emotional state of other animal species (including: dogs, starlings, mice, rhesus monkeys, pigs, chickens). By gaining a greater understanding of the positive and negative emotions of animals it is hoped that humans may be better able to meet their needs, and thus improve their welfare.

Published papers arising from Emma’s project supported by UFAW:

Paul, E.S., Harding, E.J., and Mendl, M. 2005. Measuring emotional processes in animals: the utility of a cognitive approach. Neuroscience and biobehavioural reviews. V29(3) pp 469-491. DOI: 10.1016/j.neubiorev.2005.01.002.

Harding, E.J., Paul, E.S., and Mendl, M. 2004. Animal behaviour: Cognitive bias and affective state. Nature 427, 312 (22 January 2004). DOI: 10.1038/427312a.