A theory of learning, or behavior, in terms of human development, follows the view that the focus of psychology should be behavior, the way we act. A behaviorist places value on attributes that can be seen and therefore studied, as opposed to invisible attributes, such as thinking, feelings, and other brain activities that occur without even knowing it (Craig & Dunn, 2010, p. 14). There are three important modern theorists of behavior or learning: Ivan Pavlov, John Watson, and BF Skinner. However, as stated by William Crain, John Locke was the “father of environmentalism and learning theory”, although Ivan Pavlov and BF Skinner were his “heirs” (Crain, 2011 p.3). To some, behaviorist theories may seem limiting or incomprehensible, but all major theories can be seen to play a role in our understanding of development. British philosopher John Locke developed theories in the late 17th century that a child has no intrinsic beliefs. or understanding of concepts until the child has experienced these things for himself. In his writings he stated that through observation of children's behavior, children are like an empty, unfurnished room for which one can choose the furniture, especially in the early years when children are more susceptible to suggestions and input ( Crain, 2011). Locke believed that the environment was a critical factor in development, but he also saw that how you give input to a child also influences behavior. Crain, (2011) noted that Locke believed that it was important to facilitate a child's good health and that, in addition to this, adults should help reinforce children's behavior through rewards and punishments. More than two hundred years later, B.F. Skinner saw the importance of reward and punishment. punishment while studying the work...... middle of paper ...... tson's next innovations were to remove or decondition fears, very slowly introducing the feared object in a slow, incremental and safe way until the object no longer evokes a fearful response (Crain, 2011). All of these behavior/learning theorists have made tremendous progress in understanding the psychology of human development through a rigid set of principles, through research, observation, and behavior modification experiments. One may be discouraged by the inflexible denial of cognitive processes in behavior and in relation to development. To be sure, many theories and theorists have made progress in bridging the gap between exclusively behavioral and environmental theories and cognitive theories. We must not lose sight of the fact that all these important theorists have made valuable contributions to our vision of human development, including these steadfast behaviorists.