Attention Flashcards
Why is attention necessary?
Attention is necessary for conscious perception.
Describe Broadbent’s Model of Selective Attention.
Broadbent argued that we have sensory inputs. The sensory inputs are many folds (the different senses, sound, sight, touch, etc.), and these sensors are of exceptionally high fidelity – an awful lot of information is hitting the brain at all times. The brain cannot always process this high fidelity of information– known as the ‘Limit Capacity’. So, filtering needs to occur.
Broadbent’s model of selective attention is that we have ‘Executive Functions’, which help us attend to one location in space or stream of information. Moreover, the relevant information gives it a higher level of analysis due to’ Descending Influences’. All of the descending influences filter early on in the processing timeline.
Late selection argues…
that you’ll have some early selection, but a lot of the processing of the basic information makes it through to at least ‘Semantic encoding/analysis’.
What are the difference between early and late selection?
Early selection argues that everything happens, in terms of selection, just after registration. Whereas Late selection argues that we have these filtering processes at all levels of processing.
Evidence for early selection (Cat experiment)
1) Electrode placed just behind the cochlear nucleus in the cat (cochlear nucleus is a part of the brain that is the first auditory processing station.
2) When the cat is quiet and a sound is played, this is a response in the cochlear nucleus.
3) Was used as evidence for early selection but there is a confound: the location of the direction of the pinnae (outer ears).
4) This is why we cannot dissociate between whether this is simply directional hearing or whether it is really related to attention.
So, what can we do?
We need a better experimental setup: dichotic listening task.
What is a dichotic listening task?
The dichotic listening task is simply when you listen to where the information comes into one of your ears, while ignoring the information that comes in from the other ear.
A dichotic listening task found that…
Found that the first negative (N1) deflection that you record from an EEG electrode is different depending on whether you listen to the information that comes in one ear versus the other.
Here we know that this cannot be caused by the differences in sound sources relative to your eyes.
And that is why we know, because we also know that the N1 is elicited in the primary auditory cortex that there is some early selection going on.
So, if the activities in early cortical areas differ as a function of attention, then that means there is some early selection occurring.
Evidence for early selection (Better study - improvement on cat experiment).
Better experiment used magnetic event-related field to measure attention regions of the brain during a selective listening task and then later co-registered with an MRI found that the N1 deflection comes from the primary auditory cortex.
Auditory cortical responses are affected by…
Attention
Are auditory brainstem responses affected by attention?
No, they are not affected.
Otoacoustic emissions are affected by…
Attention
What are otoacoustic emissions?
Otoacoustic emissions are a phenomenon where when you play a sound to the ear, the eardrum plays a sound back.
Whats does the fact that attention affects otoacoustic emissions suggest?
This suggests that at even very processing stages, there is some filtering going on.
Evidence for late selection
They done a typical dichotic listening task but in the unintended ear audio they sometimes added a phrase or key word important to the individual and found that they the phrase or word was played in the unattended ear the individual startled.
What does the startling to the phrase or word in the unattended to ear suggest?
That most of the information makes it too at least the level of semantic processing/analysis.
Tests for endogenous attention: Posner’s type task
Here subjects fixate at a computer screen (at the +) and they get a cue (<–, <–>, –>). The assumption is that because of the cue, we then covert attend to the target location and this would give us a behavioural advantage.
Effects of endogenous attention?
Endogenous attention effect’s reaction times, we are faster when the cue is ‘valid’, we are slower when the cue is ‘invalid’ and we are intermediate with the cue is ‘neutral’.
Event-related potential (ERP) evidence of endogenous visuo-spatial attention.
Same paradigm as the Posner’s type task but measured using ERP, you can see that when asked to attend to the left and ignore the right the ERP is much stronger than attended the side the bar is flashed compared to when you attend to another location.
Event-related potential (ERP) evidence of endogenous visuo-spatial attention.
Same paradigm as the Posner’s type task but measured using ERP, you can see that when asked to attend to the left and ignore the right the ERP is much stronger than attended the side the bar is flashed compared to when you attend to another location.
