In my study I chose to investigate partially how the environment influences cognitive judgment bias in 87 laying hen chicks and partially how personality influences interpretation of ambiguous stimuli in 49 Red Junglefowl chicks. Here I will explain how the experiment where I investigated environmental influences was performed.

All organisms can be subjected to a wide variety of environmental influences in their lifetime which can influence their judgment of ambiguous stimuli. I therefore chose to focus on two factors, stress and environmental enrichment which are common factors in the lives of animals living in captive environments. 

To investigate influences of environmental enrichment the chicks were divided into eight pens where four of these pens were barren and four of the pens were enriched. In the barren pens the chicks only had wood shavings on the floor and a water and a food bell. In the enriched pens the chicks had, in addition to food, water and wood shavings, access to perches, a house which curtains in the opening to hide in and wooden blocks on the floor which create a more complex environment (figure 1). 

Stress was investigated as both initial stress at two days of age and more immediate effects of stress at 22-27 days of age. At two days of age all chicks were put into transport boxes in groups of two to three chicks per box. For half the chicks the temperature was then lowered to 20°C for six hours while the other half of the chicks had a sstandardtemperature of 33°C. Half of the stressed and half of the non-stressed chicks were then housed in enriched pens and half in non-enriched as described above. This creates four treatments, non-enriched non-stressed, non-enriched stressed, enriched non-stressed and enriched stressed, consisting of two pens each. 

In this experiment chicks were put through two tests in order to investigate effects of the environment. One test was performed when the chicks were 14-16 days of age, before the large, unpredictable stressor was introduced. The other test was performed then the chicks were 35-36 days of age. As such effects of initial and later stress as well as environmental enrichment could be investigated.