Identify which type of study the following example describes.

Severing the connections between visual regions and the rest of the brain in animals, and observing the animals failure to recognize objects,

They are training animals in a maze and recording physiological changes in their brains, Stimulating a brain structure and recording subsequent changes in movement, Introducing two adults that are potentially attracted to each other, and then measuring their sex hormone levels, Measuring the brain volumes and intelligences of people in a group, Observing enlarged cerebral ventricles in the brains of many people with schizophrenia, Severing the connections between visual regions and the rest of the brain in animals, and observing the animals' failure to recognize an object, and Studying the relationship between a sex hormone treatment and strength of an animal's mating behavior.