Explain theories of Selective Attention.

A number of theories have been developed to explain the process of selective attention. The three of these theories are:

1. Filter theory:
   1. This theory was developed by Broadbent (1956). According to this theory, many stimuli simultaneously enter our receptors creating a kind of "bottleneck" situation.
   2. Moving through the short term memory systems, they enter the selective filter, which allows only one stimulus to pass through for higher levels of processing, other stimuli are screened out at that moment of time.
   3. Thus, we become aware of only that stimulus which gets access through the selective filter.
2. Filter-attenuation theory: This theory was developed by Triesman (1962) by modifying the Broadbent, theory.
   1. This theory proposes that the stimuli not getting access to the selective filter at a given moment of time are not completely blocked.
   2. The filter only attenuates (weakens) their strength. Thus some stimuli manage to escape through the selective filter to reach higher levels of processing.
   3. It is indicated that personally relevant stimuli (e.g. one's name in a collective dinner) can be noticed even at a very low level of sound.
   4. Such stimuli, even though fairly weak, may also generate response occasionally by slipping through the selective filter.
3. Multimode theory: This theory was developed by Johnston and Heinz (1978). This theory believes that attention is a flexible system that allows selection of a stimulus over others at three stages:
   Stage one: - The sensory representation (e.g. visual images) of stimuli are constructed;
   Stage two: - The semantic representations (e.g. names of objects) are constructed;
   Stage three: - Sensory and semantic representations enter consciousness. It is also suggested that more processing requires more mental effort. When the messages are selected on the basis of stage one processing (early selection), less mental effort is required than when the selection is based on stage three processing (late selection).