Broadbent's filter theory of selective attention and short term memory

Broadbent's theories of selective attention and short-term memory were developed as digital computers were beginning to become available to the academic community, and were among the first to use computer analogies to make a serious contribution to the analysis of human cognition. They were combined to form what became known as the "single channel hypothesis".

His Filter Model proposed that the physical characteristics (e.g., pitch, loudness) of an auditorily presented message were used to focus attention to only a single message. Broadbent's Filter model is referred to as an early selection model because irrelevant messages are filtered out before the stimulus information is processed for meaning. These and other theories were brought together in his 1958 book "Perception and Communication" which remains one of the classic texts of cognitive psychology.

Broadbent's theory accounts for a theoretical filter device, which is located in between the incoming sensory register and the short-term memory storage. His theory is based upon the multi-storage paradigm of William James(1890) and later the Atkinson & Shiffrin's 'multi-store' memory model (1968). This filter functions together with a buffer, and enables the subject to handle two kinds of stimuli, presented at the same time. One of the inputs is allowed through the filter, while the other is waiting in the buffer for later processing. The filter prevents overloading of the limited capacity mechanism beyond the filter, which is the short-term memory. It is based on the famous cocktail party problem of the British scientist Colin Cherry, who is trying to explain how we are able to focus our attention towards the stimuli which we find most interesting. Broadbent comes up with the theory based on data from an experiment where three pairs of different digits are presented simultaneously, three digits in one ear and three in the other. Most participants recalled the digits ear by ear, rather than pair by pair. Thus, if 496 were presented to one ear and 852 to the other, the recall would be 496852 rather than 489562.