Animal welfare has long been a subject under debate. Since animals are unable to voice concerns about their living standards it is of interest to find other ways to secure their wellbeing. A new measurement has been introduced where animals’ own judgement can act as an indicator for their emotional state and welfare. This study summarizes key elements from previous literature and research in order to explain the connection between welfare and judgement bias. Emotions have been defined as either an observable reaction to a stimulus or a subjective conscious experience of the stimulus. The second has been difficult to assess in animals since they cannot vocalise their own interpretations, hence emotions in animals are assessed based on the first definition. The study of animal welfare is in short the study of animal’s judgement of the world, which in turn indicate how animals feel. Cognitive judgement bias has been defined as whether an animal assess an ambiguous stimulus as negative or positive, a common method used to demonstrate this concept is the go no-go method. Animals learn to discriminate between two stimuli and is then presented with an ambiguous stimulus. The response to the ambiguous stimulus is recorded and determine if the animal is optimistic or pessimistic in its judgement. Research has been rather successful in determining factors which can affect animal welfare, opening up for deeper discussions concerning animal cognition, awareness and their effect on welfare, but further refinements are required to assess the influence of judgement bias.

Cognitive processes include biases, such as cognitive judgment bias. Cognitive judgment bias influences how the surrounding is interpreted, and this can differ between individuals. However, thus far no formal framework exists to understand how cognitive judgment bias works. Here I investigated how environmental factors and personality influence cognitive judgment bias in Gallus gallus chicks. First I investigated how two environmental factors affected the cognitive judgment bias of laying hen chicks. Chicks were exposed to stress and/or environmental enrichment, and tested in a cognitive judgment bias test before and after collective unpredictable stressors were presented. The results showed that chicks living in enriched environments were faster to reach all cues after the collective stressors than chicks living in non-enriched environments. Individual differences are often observed in animals, even when raised under identical conditions; therefore I also investigated if variation in personality influence cognitive judgment bias. Red junglefowl chicks were thereby raised in equal environments and exposed to personality assays in addition to a cognitive judgment bias test. I demonstrated that less nervous chicks were more optimistic towards ambiguous and negative cues than more nervous chicks. Also previous studies have found indications of connections between cognitive bias and environment or personality. I conclude that environmental enrichment can buffer the influence of stress on cognitive judgment bias and that personality has a small influence on interpretations of stimuli. In the future, experiments in this field should focus on exploring more aspects on how cognitive biases occurs to improve our understanding of cognitive processes.