Broadbent's filter model of attention

Broadbent's filter model is an early selection theory of attention.

Donald Broadbent based the development of the filter model from findings by Cherry, which was concerned with the issue of selective attention. Broadbent was the first to describe human's processing system using an information processing metaphor In this view, Broadbent proposed an early selection view of attention, such that humans process information with limited capacity and select information to be processed early.

Due to this limited capacity, a selective filter is needed for information processing. Broadbent stated that all stimuli are processed initially for basic, physical properties. These basic characteristics can include pitch, color, loudness, and direction. Unlike the physical properties, Broadbent believed semantic features, due to their complexity, would impose a limited capacity on the temporary storehouse of incoming stimuli. Therefore, based on physical characteristics, the selective filter allows for certain stimuli to pass through the filter for further processing, while unattended stimuli will be filtered out and lost. Further, goal-directed behaviour requires attention to be controlled; hence a high degree of selectivity is put forth in the information-processing stream. When developing his model, Broadbent emphasized the splitting of incoming stimuli to attended or unattended channels. Channel selection is guided through attention. If one is attempting to attend to a stimulus based on their current goals, they will employ voluntary attention; whereas if a sensory event catches one's attention, reflexive attention will be employed. Information selected to pass through the filter is then available for short-term memory and manipulation of the selected information, prior to storage in long-term memory.

Filter theory then postulates that a selective filter is needed to cope with the overwhelming amount of information entering the channels, such that certain messages must be inhibited or filtered out from the messages that were filtered for further processing. Filter theory reflects an early selection theory because certain information is selected and attended to at a very early stage of information processing.

During his experimentation, Broadbent made use of the dichotic listening test. This task has been used extensively to test numerous psychological phenonomena such as response times of specific auditory information, as well as testing for attended and unattended information presented to a participant. It is widely used as it is a non-invasive method of testing cerebral dominance. In a typical dichotic listening paradigm, the participant is wearing a headphone, in which a different auditory stimuli are presented to each ear at the same time, and the participant's attention is divided. The participant is instructed to attend (attended channel) the information coming from one of the ear pieces and neglect (unattended channel) the information presented from the other. Following the listening period, the participants are tested on whether they recall any information presented in the unattended channel.

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