Judgement bias in pigs is independent of performance in a spatial holeboard task and conditional discrimination learning

Abstract

Biases in judgement of ambiguous stimuli, as measured in a judgement bias task, have been proposed as a measure of the valence of affective states in animals. We recently suggested a list of criteria for behavioural tests of emotion, one of them stating that responses on the task used to assess emotionality should not be confounded by, among others, differences in learning capacity, i.e. must not simply reflect the cognitive capacity of an animal. We performed three independent studies in which pigs acquired a spatial holeboard task, a free choice maze which simultaneously assesses working memory and reference memory. Next, pigs learned a conditional discrimination between auditory stimuli predicting a large or small reward, a prerequisite for assessment of judgement bias. Once pigs had acquired the conditional discrimination task, optimistic responses to previously unheard ambiguous stimuli were measured in the judgement bias task as choices indicating expectation of the large reward. We found that optimism in the judgement bias task was independent of all three measures of learning and memory indicating that the performance is not dependent on the pig’s cognitive abilities. These results support the use of biases in judgement as proxy indicators of emotional valence in animals.

Heritabilities and co-variation among cognitive traits in red junglefowl

“…Why individual optimism may correlate with one facet of associative learning but not another is an unanswered question. To date, only a few studies have examined covariation between performance in discriminative learning and judgement biases [61,84] and have mostly reported no association between these two cognitive traits, similar to our results. However, to the best of our knowledge, links between judgement biases and reversal learning have not previously been empirically investigated.…”

Low Birth Weight Impairs Acquisition of Spatial Memory Task in Pigs

“…Cognitive development of LBW pigs has been assessed using measures of spatial learning ( 17 – 19 , 22 ) and associative learning ( 20 , 21 ). Spatial learning in a holeboard task and associative learning in a conditional discrimination task have previously been found to be independent measures of cognition in pigs ( 53 ). Perhaps no effects of LBW were found in associative learning studies with pigs because they assessed a cognitive domain that is less vulnerable to impairment as a result of LBW.…”

Pair housing makes calves more optimistic

“…Go and No-go responses were defined as during discrimination learning. Go responses in positive trials were rewarded, Go responses in negative trials were not rewarded and Go responses in ambiguous trials were rewarded to reduce potential effects of surprising non-reward [40][41][42] . According to the principles of the judgement bias task 29 , Go responses in ambiguous trials were interpreted as ꞌoptimisticꞌ responses, whereas No-go responses were interpreted as 'pessimisticꞌ responses.…”