How come parrots pupils get small when they talk?
— Brat11@sev.org IN MOST ANIMALS, the pupil, the black opening in the middle of the iris, changes size for a number of reasons. For one, pupil size controls the amount of light that can enter the eye. Changes in pupil size can also signal a change in blood pressure or an emotion such as fear, aggression, or excitement. Changes in pupil size even have been recorded during the processing of new information. In mammals such as humans, these changes are involuntary. A signal comes from a nerve in the brain and travels to the eye, telling the muscular iris to open or close the pupil. Birds’ pupils change in size for all the same reasons as humans’ do. However, they also enjoy conscious control over the iris and other eye muscles. According to avian veterinarian Dr. Susan Orosz, the signals sent from the brain to a birds’ eyes travel from some of the same nerves as in mammals, but they take a different path that allows the bird discretion over the results. In addition, a bird’s eye muscles
