Selective Attention
Selective AttentionKahneman and Treisman (1984, p.55) have succinctly described the main disagreement between early selection and late selection theories of attention: ‘The classic question of attention theory has always been whether attention controls the build-up of perceptual information, or merely selects among the responses associated with currently active percepts.’ Early selection theories hold that attention serves to select which one of a number of stimuli will be further semantically processed and stored in long term memory. On the other hand, more recent late selection theories maintain that selective attention operates after all stimuli are semantically processed. This essay briefly examines and discusses the main findings and criticisms that have caused the transition from early selection models to late selection models of attention. Apart from these two extreme positions, theories that combine aspects of both theories are also discussed.
The essential question which, if answered, would provide evidence on whether stimuli are semantically processed before or after selection is what people know about the unattended information. If the subject does not know the meaning of unattended information, this would mean that it has been discarded before it has been processed for meaning. One of the first approaches to this question was attempted by Cherry (1953, in Parkin, 1999) who carried out an experiment in which subjects were required hear two different messages simultaneously, one in each ear, but only pay attention to one of them. To make sure that subjects were not attending to the other message, they were asked to shadow the attended message, that is to recite aloud everything they heard. Subjects could report the physical characteristics of the voice in the unattended message, but not its meaning. Cherry concluded that selective attention completely overshadows the meaning of unattended stimuli. Broadbent’s (1958, in Eysenck & Keane, 1995) ‘filter’ model of attention was based on a similar experiment. Subjects were presented dichotically with pairs of digits and were instructed to shadow whichever message they preferred. A strong preference was shown for attending ear-by-ear. Broadbent theorised that stimuli are selected according to their physical attributes and unattended messages are not semantically processed and discarded. According to Broadbent, switching attention from one stimulus to another is also quite difficult.
These two previous experiments had numerous weaknesses. In Cherry’s experiment subjects were asked about information in non-shadowed messages after they had completed the shadowing phase. This information may have been perceived and processed, but forgotten later. In Broadbent’s experiment there was no particular meaning to be extracted from the pairs of digits presented, so there was no sufficient evidence to draw conclusions about semantic processing. Moreover, it was later made clear that it is possible to easily switch attention from one ear to another, when the meaning of the unattended message was relevant to the shadowed message.
Experiments by Grey and Wedderburn (1960, in Parkin, 1999) and Treisman (1964, in Parkin, 1999) demonstrated that subjects select which message to attend to...
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