Learning is of course also an element of institutional practices situated in schools, preschools, universities and other educational facilities, but it is not restricted to such environments, which, by the way, are quite recent inventions in the history of humankind. Throughout the history of research on learning, there have been conflicts regarding how to define and delimit this concept, and such discussions continue. Most definitions suggest that learning is an enduring change in a person’s behaviour that is a consequence of a reaction in a situation, and that this change cannot be explained on the basis of a native response or some temporary state of the individual such as fatigue. Learning was interpreted as the acquisition of new behaviours through conditioning, and since learning can be observed among animals as well as among human beings, its principles may just as well be studied through animal experimentation.