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In total, each hen had four test sessions each containing ten trials. Hens that received the stress treatment immediatly prior to their first test session chose the large quantity reward less frequently than hens that did not have stress treatment at their first test session.

In other words, hens stressed at their first test session showed less preference for the large reward. 

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Heart rate was measured throughout the entire test procedure. In every test, a hens heart rate was at its lowest during the ten seconds where the hen was presented with both options before allowed entry to the tunnel (decision phase). Correspondingly, the heart rate was at its highest when the hen had reached her reward. In other words, heart rate droped while the hen was in the start box to then increase when she reached her chosen option.

Heart rate during the decision phase decreased more rapidly when hens chose between balanced options (difficult decisions) than unbalanced options (easy decisions).