model pemerhatian berpilih broadbent

Broadbent's Filter Model of Selective Attention

Donald Broadbent is recognised as one of the major contributors to the information processing approach, which started with his work with air traffic controllers during the war.  In that situation a number of competing messages from departing and incoming aircraft are arriving continuously, all requiring attention.  The air traffic controller finds s/he can deal effectively with only one message at a time and so has to decide which is the most important.  Broadbent designed an experiment (dichotic listening) to investigate the processes involved in switching attention which are presumed to be going on internal in our heads.


Broadbent (1958) argued that information from all of the stimuli presented at any given time enters a sensory buffer.  One of the inputs is then selected on the basis of its physical characteristics for further processing by being allowed to pass through a filter.  Because we have only a limited capacity to process information, this filter is designed to prevent the information-processing system from becoming overloaded.  The inputs not initially selected by the filter remain briefly in the sensory buffer, and if they are not processed they decay rapidly.  Broadbent assumed that the filter rejected the non-shadowed or unattended message at an early stage of processing.

Broadbent wanted to see how people were able to focus their attention (selectively attend), and to do this he deliberately overloaded them with stimuli - they had too many signals, too much information to process at the same time.
 

One of the ways Broadbent achieved this was by simultaneously sending one message (a 3-digit number) to a person's right ear and a different message (a different 3-digit number) to their left ear.  Participants were asked to listen to both messages at the same time and repeat what they heard.  This is known as a 'dichotic listening task'.

Broadbent was interested in how these would be repeated back. Would the participant repeat the digits back in the order that they were heard (order of presentation), or repeat back what was heard in one ear followed by the other ear (ear-by-ear).  He actually found that people made fewer mistakes repeating back ear by ear and would usually repeat back this way.

Results from this research led Broadbent to produce his 'filter' model of how selective attention operates.  Broadbent concluded that we can pay attention to only one channel at a time - so his is a single channel model.


In the dichotic listening task each ear is a channel.  We can listen either to the right ear (that's one channel) or the left ear (that's another channel).  Broadbent also discovered that it is difficult to switch channels more than twice a second.  So you can only pay attention to the message in one ear at a time - the message in the other ear is lost, though you may be able to repeat back a few items from the unattended ear.  This could be explained by the short-term memory store which holds onto information in the unattended ear for a short time.


Broadbent thought that the filter, which selects one channel for attention, does this only on the basis of PHYSICAL CHARACTERISTICS of the information coming in: for example, which particular ear the information was coming to, or the type of voice.  According to Broadbent the meaning of any of the messages is not taken into account at all by the filter.  All SEMANTIC PROCESSING (processing the information to decode the meaning, in other words understand what is said) is carried out after the filter has selected the channel to pay attention to. So whatever message is sent to the unattended ear is not understood.

Because we have only a limited capacity to process information, this filter is designed to prevent the information-processing system from becoming overloaded.  The inputs not initially selected by the filter remain briefly in the sensory buffer store, and if they are not processed they decay rapidly.  Broadbent assumed that the filter rejected the non-shadowed or unattended message at an early stage of processing.

Evaluation of Broadbent's Model

1. Broadbent's dichotic listening experiments have been criticised because:

1. The early studies all used people who were unfamiliar with shadowing and so found it very difficult and demanding.  Eysenck & Keane (1990) claim that the inability of naive participants to shadow successfully is due to their unfamiliarity with the shadowing task rather than an inability of the attentional system. 
2. Participants reported after the entire message had been played - it is possible that the unattended message is analysed thoroughly but participants forget.
3.  Analysis of the unattended message might occur below the level of conscious awareness.  For example, research by Von Wright et al (1975) indicated analysis of the unattended message in a shadowing task.  A word was first presented to participants with a mild electric shock.  When the same word was later presented to the unattended channel, participants registered an increase in GSR (indicative of emotional arousal and analysis of the word in the unattended channel).

More recent research has indicated the above points are important: e.g. Moray (1959) studied the effects of practice.  Naive subjects could only detect 8% of digits appearing in either the shadowed or non-shadowed message, Moray (an experienced 'shadower') detected 67%.


2. Broadbent's theory predicts that hearing your name when you are not paying attention should be impossible because unattended messages are filtered out before you process the meaning - thus the model cannot account for the 'Cocktail Party Phenomenon'.


3. Other researchers have demonstrated the 'cocktail party effect' (Cherry, 1953) under experimental conditions and have discovered occasions when information heard in the unattended ear 'broke through' to interfere with information participants are paying attention to in the other ear.  This implies some analysis of meaning of stimuli must have occurred prior to the selection of channels.  In Broadbent's model the filter is based solely on sensory analysis of the physical characteristics of the stimuli.

sumber: http://www.simplypsychology.org/attention-models.html
p/s: harap sume bule phm..susa la nk caik rujukan in malay..xp la.anggp la neh sbgi latihan utk masuk degree nt.peace! :)