The 'cognitive revolution', and the decline of behaviourism (1956-1967). The shift within psychology from an emphasis on observable behaviour to mental processes occurred in the 1950s and 1960s. For the first half of the twentieth century, psychological research was dominated by Behaviourist principles. Behaviourists initially ruled out considering any 'mental events' occurring between stimulus and response. When psychologists such as Tolman in 1932 described experimental animals as showing 'purpose' in their behaviour, and Bartlett spoke of 'remembering', the 'empty mind', the radical version of behaviourism began to run into problems.\nWithin a decade, applied psychological research began to investigate cognitive functions like attention, vigilance and decision making during the Second World War. The rapid development of computer technology (for instance, Alan Turing's Colossus computer designed to decode German Enigma codes at Bletchley Park) during the war, and information theory shortly after, provided additional impetus to those psychologists who were interested in how humans processed information, rather than just observable behaviour. \nInformation theory was developed by Claude Shannon during his time working at Bell Labs in the USA. He published the major part of his 'Mathematical theory of communication' in 1948. The main aim of information theory was to predict the capacity needed on any one network to transmit different types of information. Shannon defined information as something that contains unpredictable news – the predictable is not information (and so does not need to be transmitted). For instance, consider the sentence 'only infrmatn esentil to understandn mst b tranmitd”. English speakers can read it easily because the regularities in English make some information in sentences so predictable that it is redundant. Information depends on uncertainty – what is certain is redundant. Shannon also argued that symbols (e.g. words, icons, mathematical equations) are used to transmit information between people. Once the information is coded into the appropriate symbols, it is transmitted (e.g. spoken, drawn, written) and decoded at the other end. To decode these symbols, the receiver must match them against his or her own body of information to extract the data. In September of 1956, the twenty-seven-year-old Noam Chomsky delivered a paper entitled 'Three Models for the Description of Language' as part of a three-day MIT symposium on information theory. This contained contained the germ of Chomsky's cognitive approach to language. Allen Newell and Herbert Simon also presented work on problem solving with a 'logic machine,' and there were papers on signal detection and human information processing. This symposium – and these papers in particular – have been considered by some to mark the launch of the study of cognitive science. Although the battle was essentially played out between traditional linguists and supporters of Chomsky's model of generative linguistics, it had implications well beyond linguistics. This was because traditional structural linguistic theories were grounded in behaviourism and learning theory, while Chomsky's work directly challenged both the intellectual and political underpinnings of traditional structural approaches to grammar, and by implication, Behaviourism. At the same time, George Miller's work on the 'magic' number seven (the supposed limit of short term memory) began work on 'chunking' and memory from an information processing perspective.Chomsky's savage review of B.F. Skinner's Verbal Behavior (1957) appeared in the influential journal Language in 1959. In a letter to Robert Barsky, the author of Noam Chomsky: A life of dissent, Chomsky explains that: It wasn't Skinner's crazy variety of behaviorism that interested me particularly, but the way it was being used in Quinean empiricism and 'naturalization of philosophy,' a gross error in my opinion. That was important, Skinner was not. The latter was bound to collapse shortly under the weight of repeated failures. (31 March, 1995). \n\nCognitive psychology has grown rapidly since the events of the late 1950s. Ulric Neisser's 1967 textbook, Cognitive Psychology, gave a new legitimacy to the field, with its six chapters on perception and attention and four chapters on language, memory, and thought. Following Neisser's work, another important event was the beginning of the Journal Cognitive Psychology in 1970. This journal has done much to give definition to the field. Of course, just as cognitive psychology didn't begin in 1956, but can trace its roots much earlier, so Behaviourism didn't stop being an influential approach in psychology at the same time. Quite apart from the lasting legacy of experimental methodology, behavioural research is still widely conducted in psychology departments today, although radical behaviourism is largely dismissed.\nIt should also be noted that some psychologists have claimed that a second cognitive revolution occurred in the 1990s, with the rise in prominence of models of situated cognition, distributed cognition, and socio-cultural and social constructionist approaches that stress the role of artefacts or tools and social interaction, as well as meaning in cognitive processes – and hence the importance of language in human interactions.