Several independent, co-occurring events around the early 1950's led to the decreased popularity of behaviorism and subsequent rise of cognitive psychology, especially information processing.
1st was dissatisfaction with and inability of behaviorism to explain higher cognitive functions.
2nd was the rise of technology which influenced several young sciences, especially communication engineering and verbal learning.
3rd was the young science of computer science--analogy between human mind and computer--limited working memory and theoretically infinite memory storage system; seen to interact to solve problems, make decisions, recognize and respond to external (environmental) stimuli. Focused on the mind as a symbol operating system.
Cognitive psychology came to be based on the notion that all information processing takes time, and that time is taken up with a series of processing stages, or steps, being performed on the information.
Measurement of reaction time became very important if you measure how long a response takes, and then change the response requirement in some way, you can determine the time required to process the changed piece of information.
For example, by degrading a stimulus we can determine how long it takes to perceive that degraded stimulus compared to a clear stimulus.
Reference: http://home.sandiego.edu/~taylor/coghist.html has no name
Second World War
During the Second World War it became apparent that fighter pilots had difficulty in flying and paying attention to the information on the large number of dials in front of them. Psychologists such as Broadbent were brought in to advise on how the instrument panel could be redesigned to improve the pilot's performance. Thus in an applied setting psychologists began considering more than just overt behavior.