It is important to note that learning can occur without a change in behavior. According to J.E. Ormrod's general principles of social learning, while a visible change in behavior is the most common proof of learning, it is not absolutely necessary. Social learning theorists believe that because people can learn through observation alone, their learning may not necessarily be shown in their performance. These are interdependent on each other and its influence can be directly linked with individual or group psychological behavior. According to Alex Stajkovic and Fred Luthans it is critically important to recognize that the relative influences exerted by one, two, or three interacting factors on motivated behavior will vary depending on different activities, different individuals and different circumstances.