The science of psychology as a whole has its earliest roots in Greek Platonic philosophy which studied the functions of the mind (Grider, 1993). From the beginning of its history and throughout its development as a science the form, function, application, and relevance of psychology has been hotly debated by many venues of the scientific and academic worlds (Harzem, 2004). In the late 1800s the earliest psychological research had its basis in physiological experimentation on how the nerves and the brain worked together to produce observable actions and behaviors in animals. As time went on this, what was termed "applied" psychology evolved into many other forms of experimental psychology based on the researchers' views of how psychological testing should be conducted and applied (Hoffman, 1992). One of the strongest forms of psychology that evolved during the 19th century was that of Behaviorism. Behaviorism, although having its roots in comparative psychology, was largely an American phenomenon, as it emphasized the importance and possibility of learning through perseverance. There were many psychologists that changed and improved the theories and practices of American Behaviorism through the ages, some the most influential were John B. Watson, B.F. Skinner, and Edward C. Tolman (Goodwin, 2008).

John B. Watson
In a presentation delivered at Columbia University in February of 1913, John B. Watson knowingly or not laid out the foundation of what is now called the Behaviorist Manifesto. The Behaviorist Manifesto, or "Psychology as the Behaviorist Views It" (Goodwin, p 342, 2008) in brief assigned psychology to the natural sciences, articulated a clear set of goals, rejected introspective based psychology, and accepted an evolutionary model of behavior (Goodwin, 2008). In 1900 Watson attended Furman University and exhibited an early interest in comparative psychology. With the added quality of an inherent love of animals, Watson soon decided that he could learn just as much from observing animal behavior as other students were learning about human behavior by observing humans. Watson began experimenting with mazes and white rats and their observable learning behaviors from birth through the fourth week of age. Eventually, while working with Harvey Carr at the University of Chicago, Watson began removing sensory organs in an attempt to establish a connection between the rats' learning process and kinesthetic sensory perception. Watson found that the kinesthetic sensory perception was only partially responsible for learning the sensory stimulus had to be paired with cognitive processes to produce learning (Goodwin, 2008).
In 1908 Watson accepted a position at Johns Hopkins and established a wide-ranging animal behavior research program. During this period Watson began his psychophysics research which held that animals were capable of perceiving differences if not in color at least in shade because they could be conditioned to respond to one color but not to respond to a different shade of the same color. This discovery added a whole new layer in perception to animal behavior and the possible applications of conditioning. Watson held that there was no difference between training an animal and training a human being, "no dividing line between man and brute" (p 343) for this reason Watson argued that psychology should not be the focused on the study of consciousness, but rather become a science of behavior. He pointed out that just as the study of animal behavior had allowed psychologists to predict and control behavior these methods could be applicable and useful with humans as well. These arguments made behaviorism popular in America because it allowed for real life application of psychological principles.
From here Watson moved on to study fundamental human emotion and development. In a research study known as "Little Albert" Watson conducted a series of experiments on an infant in which he was able to produce a fear of a white rodent (and then rabbit) by introducing it to the child while paired with a loud noise. The loud noise elicited an instinctive emotion (fear) in Little Albert because of the pairing of the noise with the rat soon only the presentation of the rat elicited the same response. This research led to his eventual research and collaboration in systematic desensitization with Mary Cover Jones.
During the 1920s Watson lectured on behaviorism but spent a good deal of his time as a marketing executive. Watson had a large impact on business by applying scientific strategy to marketing practices such as using demographics to better target marketing efforts and developing training programs for personnel. Watson did a great deal for the concept of behaviorism by championing it everywhere he spoke and by publishing articles in his early career and throughout his professional life (Goodwin, 2008).

B.F. Skinner
Building on the work of John B. Watson, B.F. Skinner carried behaviorism to a whole new level. Skinner developed his theories of behaviorism while at Harvard in the 1930s. Skinner was a close follower of Pavlov and Watson having conducted major studies in conditioning. Skinner furthered the study by developing the theories of operant conditioning which holds that repeated behavior is directly dependent on the positive or negative consequence of a behavior whether stimulated in the same way or not, the environment being one of the man causes for determination of repeating ceasing a behavior (Goodwin, 2008). Skinner studied operant conditioning by creating highly structured and completely controlled environments that came to be known as Skinner Boxes. All actions taking place within the box were recorded cumulatively for later analyzation. Using this type of completely controlled environment Skinner was able to exhibit several various conditioning phenomena such as extinction, generalization, and discrimination all of which Skinner referred to as stimulus control. Skinner did not believe in hypothesizing and then conducting experiments to prove a nebulous theory, he preferred inductive research; studying samples of regular behaviors in order to establish general principles. By the late 20th century there were basically two forms of psychology; behaviorism and everything else (Malone, 2001). Although Skinner was never elected to the APA presidency, he is none the less one of the most noted historical behaviorists among scholars and psychologists (Goodwin, 2008).

Edward C. Tolman
Edward Chance Tolman was destined for a career in electrochemistry having graduated from Massachusetts Institute of Technology (MIT) in 1911. His father was a prominent physicist and Edward was headed in the same direction until he came across the writings and theories of William James. Inspired by James' Principles, Tolman chose introductory philosophy and psychology when enrolling in graduate courses at Harvard. Although Tolman recognized the merits of Watson's behaviorism, he did not feel that behavior could be reduced to simple muscular and glandular stimuli and response. Tolman argued that one of the key elements of behavior is cognitive purpose. Tolman emphasized a more Gestaltist overall or as he put it "molar" emphasis on studying behavior. That is to say that Tolman believed that learning and cognition could not be broken down into single elements of stimuli and muscular response but that the entire organism was involved in learning. Tolman proved this goal-directed, purposive behavior by experimenting with rats and mazes, sometimes offering food at the end of the maze, sometimes not. He found that although the rats learned the maze with or without the stimulus of food but their intensity and speed with which the rate coursed the maze was affected by the offer of reward. This discovery led Tolman to his theory of intervening variable. Expectancy then, was a huge determinant of performance whereas learning was accomplished by a process of "cognitive mapping" on a latent level. Learning occurs either way, but certain expectations are developed during the learning process. This theory is better known as Tolman's latent learning theory. Tolman's combination of theoretical speculation with laboratory testing proved that learning was not dependent upon reinforcement but occurred on unconscious levels in an overall cognitive and purpose driven manner (Goodwin, 2008).

Comparing Perspectives
Behaviorism has developed in many different directions because of the different perspectives of the psychologists and researches involved. With vast number of intelligent and inquisitive minds pondering the workings of the human and animal psyche it is no wonder that there was wide debate and sometimes outright dissension. Theories and research were conducted all over the world at a phenomenal pace and many researchers today theorize that some of the disagreement experienced among schools of thought may have had more to mistranslation than to actual disagreement on principles. Major works were translated in many languages, however more minor works (or those considered minor at the time) were not as widely translated or circulated (Kilgour, Murray & Wasylkiw, 2000). In America at least behaviorism kept making strides forward toward applicable use in society through the work of Watson, Skinner, and Tolman.

References
Goodwin, J.C. (2008). A history of modern psychology, (Third Edition) John Wiley & Sons, Inc.
Grider, C. (1993). Foundations of cognitive theory: A concise review. Document resume. ED 372 324. CG 025 617. Retrieved May 3, 2010
Harzem, P. (2004). Behaviorism for new psychology: What was wrong with behaviorism and what is wrong with it now. Behavior and Philosophy, 32, 5-12. Cambridge Center for Behavioral Studies. Retrieved May3, 2010.
Hoffman, R.R. & Deffenbacher, K.A. (1992). A brief history of applied cognitive psychology. Applied Cognitive Psychology, Vol. 6, 1-48. John Wiley & Sons, Ltd. Retrieved May 3, 2010.
Kilgour, A.R., Murray, D.J., & Wasylkiw, L. (2000). Conflicts and mixed signals in psychoanalysis, behaviorism, and gestalt psychology. American Psychologist, April 2000. Retrieved May 3, 2010.
Malone, J.C. (2001). Radical behaviorism and the rest of psychology: A review/précis of Skinner's about behaviorism. Behavior and Philosophy, 29, 31-57. Cambridge Center of Behavioral Studies. Retrieved May 3, 2010.