The avian class is characterized by particularly strong variability in their domesticated species. With more than 250 breeds and highly efficient commercial lines, domestic chickens represent the outcome of a really long period of artificial selection. One characteristic of domestication is the alterations in brain size and brain composition. The influence of domestication on brain morphology has been reviewed in the past, but mostly with a focus on mammals. Studies on avian species have seldom been taken into account. In this review, we would like to give an overview about the changes and variations in (brain) morphology and behavior in the domestic chicken, taking into consideration the constraints of evolutionary theory and the sense or nonsense of excessive artificial selection.