The cognitive approach to human and comparative psychology rests on two main assumptions: 1) there are cognitive representations and processes that act on those representations 2) we can discover these representations and processes, albeit indirectly (Willingham, 2007). This approach offers a middle ground between B.F. Skinner’s cut-and-dry input—output relations and C.L. Hull’s hypothetical constructs and intervening variables. In the first case, there is no room for intermediary cognitive processes between stimulus and response, outside the realm of simple associative learning. In the second case, there is lacking an explicit scientific means by which to objectively observe the theoretical cognitive mechanisms in question. However, E. C. Tolman was one of the first psychologists to suggest that intermediary cognitive processes could be deduced through the results of scientifically rigorous experimentation (Zentall, 2002). It is on this very basic proposition, that theoretical cognitive processes can be inferred by observing behavior, which most informs the developmental milestones in the formation of the cognitive perspective as a branch of psychology.

Development of Cognitive Psychology
The development of the cognitive approach as a mainstream psychological perspective is marked by four major milestones: 1) the shortfalls of the behaviorist perspective of psychology 2) the ability for abstract constructs to account for the aforementioned shortfalls 3) the bridging of abstract constructs with observable mechanisms through the medium of artificial intelligence and neuroscience 4) the realization that the representations and processes of cognition can be liken to the internal functioning of a computer. The behaviorism of the early 20th century could not account for many observable behaviors documented by psychologists of the time. For instance, the associative