Chicks form memories when still within their eggs. When they hatch into the world, their sensory systems are already so well developed they are able to recognize and learn from the mother hen within hours. As they grow, chickens realize the importance of the flock as a protective and stable social group; they learn where they fit in among flock members, and they come to memorize and recognize the faces of over one hundred other chickens… They grasp abstract concepts: young chicks recognize objects which have been partially obscured, a feat beyond the ability of small children. Chickens also anticipate the future, and thereby have the capacity to experience anxiety and frustration.
— Annie Potts (The Joy of Chickens)