early and late attention Flashcards
What is attention
Attention implies selectivity; by focusing on a piece of information we filter out the other irrelevant input
Intuitively this appears to function to protect a limited capacity system
Why it’s important to know what happens to unattended stimuli
Tells us where the processing limitation is occurring in the series of cognitive processes that occur: perceptual, semantic, action and memory.
Which experimental approaches have been used
Evidence from neglect patients, selective auditory attention and selective visual experiments support both theories of attention.
What evidence supports the early selection theory
Limited capacity for processing the meaning of stimuli
Unattended items should be processed only in terms of their basic perceptual features
What evidence supports late selection
Limited capacity for responding to stimuli
How perceptual load theory reconciles the evidence
Attention as flexible
Important insight into how cognitive functions arrive in the brain through interactions amongst a network of brain regions
However there are apparent limitations in the data this explains
Early selection theory
Limitation occurs early in processing
High capacity to extract perceptual information from scenes but limited capacity for processing the meaning of stimuli
Locations and features are selected
If true, unattended items should be processed only in terms of their basic perceptual features as only attended information gets processed for meaning to then be acted on or remembered.
Cherry (1953) Dichotic listening
The degree to which people were able to attend to one message effectively and what happened to the information coming from the unattended message
Manipulation to make sure people were paying attention to one particular message - asked participants to shadow by repeating one of the two messages out loud
When attending to one ear subjects notice or remember very little from the other ear
They notice if speech is replaced by a pure tone, but not if the message switches to German or even is played backwards
Distinction is between basic perceptual features vs meaning.
Rock & Gutman (1981) effective selection by colour
Participants presented with a series of picture pairs in red and green.
Told participants to ignore the green and just pay attention to the red
Had to rate the red objects in terms of pleasantness
Were then given a surprise memory test
Found that participants were slower at chance recognising the green items
Consistent with early selection
Visual neglect - early
Patients with damage to the right parietal cortex are often entirely unaware of unattended items in the neglected/ contralesional hemifield
E.g fail to copy the LHS of pictures
Late selection
High capacity for processing information both perceptually and semantically
The limitation occurs in the capacity of action in response to stimuli whether that is acting on it or remembering it.
Meaningful objects are selected
If true the semantics of unattended stimuli should be processed
Marshall & Halligan (1988)
Single-case study of patient PS provides evidence of processing of information without awareness in the neglected hemifield
PS consistently said she’d prefer not to live in a house that had flames fanning out of a LHS window, despite reporting the house looked identical to another without flames.
Suggesting that even if information is not getting through to awareness it seems to be processed to a high level and some meaning appears to be extracted as evidenced by the patients preference to live in the house that is not on fire.
Evidence of late selection and high level processing of information even if the patient is unaware of it
Tipper (1985) Negative priming of ignored stimuli
Replicated the effect that people have very poor memory of information they are not interested in
Subtle effects that show that even if the participant can’t remember information they didn’t attend to they may have still processed this
Asked to attend to one item (e.g in red) of an overlapping pair by naming it while ignoring the other (e.g in green)
See a series of images. Sometimes the item that had previously been ignored would appear as the item to be named on the next trial.
Interested in whether ignoring an object on one trial has a measurable effect on the next trial - particularly how quickly participants were able to respond.
Participants were slower to respond if the next red item was the ignored green item on the previous trial.
consistent measurable difference in terms of participants being significantly slower to respond to an item that they had previously ignored.
Phenomenon referred to as negative priming effect
Suggests that even if an item is ignored its processed such that if you’ve ignored it you’re slow to respond now
Importantly it was shown that this effect generalises - seeing dog on trial n, makes you slower to name a cat on trial n+1.
Therefore generalises across meaningfully similar items - so meaning must be extracted (despite not being remembered)
Corteen & Dunn (1974)
Repeating the general approach that Sherry took of playing participants different messages in each of the two ears, asking them to shadow one message and see how much processing there was of words in the unattended message.
Before experiments, participants were classically conditioned to expect an electric shock whenever they heard the city names
When asked to press a button to indicate whenever they heard a city name participants essentially never did
Using a subtle measure they were able to show that nevertheless participants must have been processing those words even if they didn’t respond to them
Picked up sweat using electrodes to measure conductance of their skin - galvanic skin response
Subjects may not consciously notice or remember unattended words in dichotic listening, but they show a skin conductance response to words that had early been paired with an electric shock, in this case city names.
Importantly, this effect generalised to other city names.
Important evidence that it is the meaning that is being processed as this response was shown even to city names that they hadn’t previously been classical conditioned with.
Kastner et al. (1998)
fMRI - interested in the degree to which attention modulates activity in the different parts of the ventral stream and areas V1, V2, V4 and TEO.
Shows evidence of early and late selection in a single set of results
Attention modulates processing the earliest cortical visual areas (V1 and V2), suggestive of early selection (blood flow response as a measure of activity)
Unattended items elicit activity even in high-level visual areas (V4 and TEO), suggestive of late selection
Collectively these rule out both early and late selection theories
The framing of early and late selection may be misconceived as this suggests the human brain is more flexible in terms of what it selects.
