Among the most fascinating areas in the biological sciences is ethology, or the study of animal behavior—in particular, the areas of ethology that deal with instinct and learning. Instinct is a stereotyped, or largely unvarying, behavior that is typical of a particular species. An instinctive behavior does not have to be learned; rather, it is fully functional the first time it is performed. On the other hand, learning, in an ethological context, is the alteration of behavior as the result of experience. Clearly, the distinction between instinct and learning revolves around the question of whether an animal, in responding to a specific situation, is acting on the basis of experience or instead is guided by instincts "hardwired" within its brain. The difference would seem to be a simple one, but nothing is simple in the study of instinct and learning. Plenty of gray area exists between pure instinct and genuine learning, and within that gray area is a fascinating concept known as imprinting, or the learning of a behavior at a critical period early in life, such that the behavior becomes permanent.