In the aerial predator test and the emergence tests where the effect of stress on the behaviour was assessed, the RJF genotype birds behaved significantly different from the WL genotype birds. α2C-ARs control adrenaline release from the adrenal glands (Brede, 2003). Adrenaline is the major hormone released during the classic stress response (also called the fight-or-flight response). α2-ARs are extensively present in the bed nucleus of the stria terminalis (BSt) in chickens’ brain (Díez-alarcia, 2009). BSt is associated with reactions to both acute and chronic stress in mammals (Fendt, 2005).
 

Male RJF genotype birds solved the learning test with significantly lower number of mistakes. α2C-ARs expression can lead to change in brain dopamine level (Sallinen, 2007). Dopamine plays a major role in the brain system that is responsible for reward-driven learning. α2C-ARs are the dominant α2-ARs in the striatum (Holmberg, 2003). Current evidence suggest that the striatum contributes directly to decision-making (Aoki, 2006).

To reach fixation, the newly arising beneficial alleles should have substantial adaptive advantages. We did not find important adoptive advantages for neither of the studied genotypes. More research is needed to find out “if” and how the variation on the ADRA2C gene has played a role in domestication of layer chicken.