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Chapter 3

PSL440Y1 Chapter Notes - Chapter 3: Frontal Lobe, Thalamus, Hemispatial Neglect

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Chapter 3: Attention
Attention is the process that enhances some information and inhibits other information. The
enhancement enables us to select some information for further processing and inhibition allows
us to set some information aside
Attention has three components; orienting to sensory events, detecting signals for focused
processing and maintaining an alert state
Failures of Selection
When there is a lot of information simultaneously present in front of us, we fail to notice all the
information all at once. This failure is referred to as failures of selection in space
When new information arrives in a rapid stream, spending tie processing it will cause us to
miss some other incoming information resulting in failures of selection in time
These failures to attend to information are a by-product of a system that prevents us from
becoming overloaded with irrelevant information and use a system of selective attention
Failures of selection in space
An experiment was conducted where experimenter asking for direction was changed.
Change blindness: is the failure to detect changes in the physical aspect of a scene
Change deafness: is the failure to detect changes in the auditory aspect of a scene
The selection of information is not by chance but we select only partial information from the
world and leave out the unimportant information
Changes in central interest; those that are related to the thematic content of a scene are
detected much more quickly than changes of ‘marginal interest’
Attention is controlled and driven by top-down processing which can change in flexible and
dynamic manner
Our knowledge, beliefs, goals and expectations can alter the speed and accuracy of processes
that select meaningful and desired information from the flood of inputs
When there are too many competing stimuli, the top-down processing may be overrriden by a
sensory event i.e. by bottom up processing
We may also fail to attend to information in space when although there were fewer stimuli but
you are required to pay attention to two stimuli at once
Concentration on one source of input to the exclusion of the other is known as focused
When more than one source of information is attended at the same time, the information
selected is imperfect and leads to divided attention
The loss of information when attention is divided may be because of limited attentional
resources; mental effort. When the available capacity is less than required for completion of a
task, failures are frequent
Failures of Selection in Time
We have limitations in terms of the amount of information that we can register at a particular
period of time
Attentional blink is a short period of time during which incoming information is not
registered similar in effect to the physical blanking out of visual information during the blink
of an eye. The phenomenon of attentional blind also occurs for two objects that are presented
in rapid succession. We detect the earlier stimulus and fail to detect the latter.
A similar type of effect involves failure to detect objects presented in a rapid sequence wehen
some of these stimuli are identical even when the stimuli are shown for a long enough time to
avoid the attentional blink. E.g. study where the first and third stimuli were identical but people
failed to notice it and registered the information as just one stimuli
Repetition blindness is the failure to detect the later appearance of a stimulus when the stimuli
are present in a rapid sequence. Such type of blindness can occur for words as well as for
Blindness to a repetition can also be observed if several words come between the 2 instances of
the repeated word or even if the repeated ones are written in different styles. The second event
is just assimilated into the first one
Sources of Limitation
Limitation is not due to vision but it has to do with the quantity of information.
Bottleneck is a restriction on the amount of information that can be processed at once; because
of bottleneck some critical mental operations have to be carried out sequentially
Divided attention studies demonstrate that performance is hampered when we attend to two
stimuli simultaneously
Dual-task interference: refers to the added cost in accuracy or reaction time when you attempt
to perform two tasks at once.
The decrement in the performance is greater when the source of the information is similar e.g.
both visual and less when we are attending to information from two different sources e.g.
visual and auditory
The failure to select information can occur even if the information is presented through two
different sensory modalities
The extent of interference also depends on the extent of ‘cross-talk’ between the
representations and processes; if similar processes and representations are activated in the two
tasks then they may be confused
A bottleneck in attention can also occur when even with a single sensory input you are required
to provide two outputs – i.e. you cannot do two tasks at a time. This corresponds to the failure
in motor output when we try to do a number of things at once and this is not because muscles
cannot move fast but because brain needs to organize the processing
Response bottleneck: The interference in the form of as slowing down of your actions and
arises when we try to select between two possible responses through a single sensory stimulus
The effect of response bottleneck has been observed in driving where drivers try to use
cellphone and drive at the same time – which creates a problem and leads to accidents. Study
was conducted to test the difference between use of a cellphone, use of a hands-free cellphone
and listening to radio. Although, divided attention was observed in all cases but were more
pronounced when people were talking rather than listening
Problems in Interpretation
An effective strategy for multi-tasking would be to simply switch back and forth between the
two tasks rather than fully deal with the two situations simultaneously. But the problem is how
do we decide the amount of time to spend on each task and when to switch to a different task.
When we dual-task, often dual-tasks morph into a single task and make it difficult for us to
separate out and quantify performance on each of the tasks. Also, in this procedure of task