Cognitive bias and anticipatory behaviour of laying hens housed in basic and enriched pens

The performances of adult laying hens, housed in either a basic or an enriched pen, were investigated in a cognitive bias and an anticipation test. Both tests were designed to measure the assumed emotional state of the birds. The behaviour of birds in each test was compared to see whether both tests provided similar evidence of changed emotional state. In addition, measures of fear and negative social interactions within the home pen were taken, and their association with the measures of emotional state were examined. No significant differences between treatments were found, which suggests that the basic and enriched pens did not induce large enough differences in the birds' emotional state to have a significant impact on their behaviour in the tests. On the other hand, the number of social interactions exhibited in the home pen correlated with some aspects of behaviour in the anticipation tests and the amount of training needed to reach testing criteria in the cognitive bias tests correlated with latencies to approach the near rewarded probe in the same test. This suggests that when animals are not put under more severe treatment differences, other individual differences have a greater impact on how they perform in the tests. (C) 2012 Elsevier B.V. All rights reserved.