lecture 5- attentional modulation of perception

Question 1

Why do we need attention?

Answer 1

1) Limited capacity for processing information, at any time only a small amount of the information available on the retina can be processed and used to control behaviour

2) Selectivity, ability to filter out unwanted behaviour

The two mechanisms of selective processing are top-down and bottom-up

Question 2

Explain the visual search paradigm

Answer 2

searching for a single target amongst distractors.
- Certain features: colour, orientation and shape help the target to stand out from the other distractors.
- We can do this so quickly without having to focus attention on each item, instead we process all of them slightly to recognise they are different colour, then the different colour grabs our attention.
- This is Parallel search

• When we search for a target defined by a conjunction of features, more attention to each is required. The target is less homogeneous.
• This is serial search as each item must be looked at in more detail/ top-down processing
  ○ Takes longer if there are more distractors unlink parallel search

Question 3

How does spatial attention impact other processes

Answer 3

• Moving attentional spotlight in space to actively search for object usually by moving eyes around
• Not only are objects processed better, but other objects get ignored
• We can choose to voluntarily move out attention (top down) or it can be involuntarily drawn (bottom up)

Question 4

What are the behavioural effects of spatial attention

Answer 4

Posner’s cueing paradigm: reaction times are quicker and responses are more accurate in the valid cue trials.
- Attention paid to an object without moving our eyes to it is called covert attention if we focus on the object is overt attention.

It has been suggested that paying attention to a stimulus changes the perceptual appearance of it.

Focusing attention to a specific region can improve accuracy, enhances contrast too

Question 5

How do we have selectivity for features

Answer 5

As well as paying attention to an area in visual space, we are able to select what to process on the basis of visual features such as colour- this is feature based attention

Desimone and Duncan 1995: people shown letters (some black some white) on a blue background and asked to report only black letters.
- Limited capacity is shown by reduced accuracy when the number of targets is increased
- Selectivity is shown by negligible impact of non-targets. There is not much change when there is lots of distractors and only a few distractors (white letters)

Question 6

Attention and feature binding

Answer 6

To perform a conjunction search, it seems as though we must focus attention serially on each item in the search array to bind the properties at any given location
When attention is focused elsewhere, we can experience illusory conjunctions

Question 7

What are illusory conjunctions

Answer 7

perceptual errors where we incorrectly combine features of different objects into a single illusory object. Without the time to serially process and pay attention to each item, we cannot bind the features together correctly.
- More frequent for brief exposures during which attention is diverted elsewhere

Question 8

What are conjunction errors

Answer 8

more frequent than reports of a colour or shape that was not present, suggesting the errors reflect a genuine exchange of properties rather than simply misperceptions of a single object.

Question 9

What is inattentional blindness

Answer 9

not noticing something when we are not paying attention to it. This is not something we are actively aware of. Even though we are typically very good at detecting change
- Very large changes central to where you are looking are difficult to detect
- Frames placed between two picture frames can disrupt attention and make it hard to recognise change between the two.

Question 10

What are some factors which may impact attention

Answer 10

• Selectivity for features
• Difficulty of the task
• Salience
  Expectation

Question 11

Tootell and Dale 1998

Answer 11

asked participants to keep eyes fixed while paying attention to one quadrant and ignore the others.
Found that the area that responded to a quadrant, responded more when it was being attended/ when they were asked to pay attention.
The visual input stays the same, but the level of attention change has an impact.

Question 12

What is the neuropsychological evidence for attentional mechanisms

Answer 12

right-hemisphere damage leads to neglect- lack of ability to pay attention and extinction- paying attention to one area wipes out ability to pay attention to other areas.
Bisiach and Luzatti 1978 patients with neglect asked to visualise a piazza familiar to them from two opposite ends, each time they only described the right hand side. Attention deficit can impact visual memories.

The parietal network is involved in attention and damage to right parietal region effects ability to notice other regions of space despite intact eyes and other visual brain regions. May be involved in guiding visual attention