The chickens were put through a series of five behavioural test, assessed to measure either feafulness or social behaviours (sociality and aggression). 

• Tonic immobility test. in this test a predator attack is stimulated by an experimenter, to which the chicken elicit a predator responce, "death feigning". Tonic immobility is an unlearned response to physical restraint, and is characterized by motor inhibition, reduced resonsiveness to external stimulation and temporary suppression to the righting response. Animals with longer tonic immobility duration and fewer induction attempts are normally considered to be the most fearful ones. 
• Fear of humans. The animals response to a human was tested using the arena in fig 1. The variables measured was latency to leave tha start box, latency to approach the human, latency to start eating from the hand, and number of pecks in the hand. 

• Aggression test (mirror test). The birds aggression towards an unfamiliar bird was tested in an arena in which one side were covered of a mirror. Chickens do not recognize themselves in a mirror, which means that they were faced with a total stranger in the arena; birds with an aggressive approach to the stranger, met a likewise aggressive bird, whereas birds with a submissive approach were faced with a submissive stranger. Alla aggressive behaviours were counted (attack, ruffling feathers and waltzing) as well as how close to the mirror the birds were. 
• Open field test. In this tests the birds reaction to a novel, open space is measured. Birds that are inactive in the open field are usually considered more fearful. 
• Sociality test. This test measured the birds social vs explorative tendencies, through a set up with companion birds and a novel arena. The companion birds had no visual contact with each other, but full visual contact with the test bird, see fig 2. The social test was measured by how much time the test bird spent in each of the zones (social, middle and asocial zone), as well as how much the bird moved in the arena.