Review data relevant to the distinction between early-selection and late selection in models of attention. Describe briefly the compromise position adopted by Lavie and colleague(s) in the `perceptual load' framework
Title: Review data relevant to the distinction between early-selection and late selection in models of attention. Describe briefly the compromise position adopted by Lavie and colleague(s) in the `perceptual load' framework
Attention is the ability to take a hold of the mind and select one from many simultaneous objects or thoughts, discarding some things in order to deal with others more effectively (James,1890, as cited in Norman, 1976) . In every day life there are so many things that can be attended to and so certain aspects have to be selected over others. Some tasks that are carried out require very little attention and others require less the more time that they are practiced. All sensory information that is received requires some cognitive processing however with attention, cognitive processing needs to be continuous in order to keep focus and concentration. Attention is something that could be said to be limited, as cognitive processing cannot occur for all stimuli at the same time. It also is selective as the mental energy required for attention can be expanded as the person sees fit. Attention is an issue that has been debated upon for many years. Early-selection models have looked at selection as a limited process that requires selective attention in order to proceed. The selective attention occurs after a basic analysis of the physical features that are used to tell the difference between selected and non-selected stimuli. As a result of this, the unattended stimulus is not completely perceived. Late selection models however discard this idea and assume that perception is unlimited and that attention can be performed in parallel without a need for selection. (Lavie and Tsal, 1994) Both the late selection models and early selection models differ in their concepts of how people attend to things and it was only until a compromise model was put forward by Lavie and colleagues that both models were combined to form the perceptual load framework.
The idea of how we attend to more than one thing at a time has always been an issue. Colin Cherry (1953, as cited in Eysenck and Keane, 2001) looked at this idea when at a party he was fascinated with how people were able to follow just one conversation when there are many other conversations taking place around. He called this idea the ‘cocktail party effect’, and put it down to physical differences, like gender, speaker location and voice intensity. Cherry carried out a number experiments on this idea and did this by presenting subjects with two different messages at the same time, one in each ear. Cherry found that when the messages were of the same voice then the listener was unable to distinguish between either of the two different messages. Cherry then carried out studies in which he asked the listeners to ‘shadow’ one of the two messages heard. He found that the listeners could extract very little information from the non-shadowed message, and barely noticed when the non-shadowed message changed language or was even read backwards. Moray (1959, as cited in Kahneman, 1973) tried to look at how much information a subject could remember in the rejected auditory channel and so repeated an english word 35 times in one of the ears. He found that even though the subjects had heard the word many times, many of them still could not retain what it was. Cherry concluded from his work that unattended information receives hardly any processing, which follows the early selection model ideas that attention is not processed in parallel.
Broadbent (1958, as cited in Eysenck and Keane, 2001) developed Cherry’s ideas further by conducting an experiment on participants in which he presented them with two sets of numbers in each ear. For example the number 354 was presented in one ear at the same time as the number 692 was presented in the other ear. Broadbent found that participants recalled the numbers ear by ear rather than as a whole number, for example 354692 instead of 365942. Broadbent explained his findings by saying that both the inputs are presented in parallel fashion until they reach a buffer where one input is allowed to pass through and the other remains for later processing. This he explained is to prevent an overload. From his discovery Broadbent went on to construct a model from which he felt best described how attention is processed. This model was called the filter model. The filter model put forward the idea that the ability to analyse and identify information is limited. He argued that when information reaches the brain it filters out desired messages and rejects everything else, therefore blocking undesired inputs and preventing an overload on the perceptual system. (Dittrich, 2004) When information is presented it is analysed based upon its physical characteristics. The information is then simultaneously stored in separate channels in the sensory register and the filter switches between channels passing the information stored there, one channel at a time, to the detection device. If the message coming in doesn’t have these characteristics then it is filtered out. Broadbent’s ideas were the beginning of many years of further research. This begun with a referral back to Cherry’s questioning of how people can switch their attention from one input to another when they are unaware of the content within the unselected input. Gray and Wedderburn (1960 as cited in Kahneman, 1973) looked at this and ignored Broadbent’s idea that attention was the basis of an analysis of physical characteristics. They believed that psychological aspects played an important part and so carried out experiments to try and prove their theory. The experiment involved presenting subjects with words broken down into syllables. Each syllable was presented alternately to each ear. At the same time another word was broken down the same way and was presented to the complimentary ear. Gray and Wedderburn found that words could be constructed and were not repeated as just a mixture of different syllables. This suggested that meaning of information can be constructed from both ears and it is not just physical characteristics like Broadbent had previously said.
