Human attention

Question 1

What are the several types of attention (and inattention)?

Answer 1

1) selective attention → filter out irrelevant material to select the relevant
2) sustained attention → maintaining processing on current goals over extended periods of time
3) executive control of attention/ cognitive control → control over processing when the response is not the automatic one or there are conflicting potential responses

Question 2

Define attention

Answer 2

The process by which certain criteria are selected from further processing while others are disregarded - this increases the efficiency of processing and prevents sensory overload

Question 3

What is a good demonstration of how selective our attention actually is?

Answer 3

Change blindness in videoclips

Question 4

Why is understanding the limits of attention important in a clinical setting?

Answer 4

to ensure that the patient actually takes in the recommendations - patients less likely to encode relevant information under stress

Question 5

What is bottom-up selectivity of attention?

Answer 5

Where salient information in the environment captures brain processing, (sensory changes which we arnt really looking for) e.g. an abrupt change in the visual field such as onset of motion capture attention readily because they may be important for survival

Question 6

What is top-down selectivity of attention?

Answer 6

where processing is selectively directed towards specific information, e.g. when looking for someone in a red coat in a large crowd

Question 7

Whats a classical example of inattentional blindess?

Answer 7

The moonwalking bear awareness test - subjects are told to count the nuber of basketball passes between players and do not notice a moonwalking bear passing through the scene
This test was developed as a publicity stunt to warn drivers of the dangers of not being aware of cyclists while driving

Question 8

What gives us an idea of where spatial selective attention is depolyed?

Answer 8

Our gaze

Question 9

Who showed the top down regulation, how and when?

Answer 9

Yarbus (1967)
Presented subjects with Ilya Repin’s painting ‘The Unexpected Visitor’ under a number of conditions:
- when no particular task was given, recording of gaze movements revealed that attention concentrated on people and specifically, their faces
- However, when goal-directed tasks were given (e.g. to assess the ages or material circumstance of people in the picture) the gaze shifted to cues

Question 10

Discuss how attention can also be directed covertly

Answer 10

In the periphery of the gaze, were we enhance attention outside of the centre of our gaze - this comes at a cost of worse performance at other (non-attended) spatial locations

Question 11

Discuss Posner’s experiments

Answer 11

• observers maintained central fixation, staring at a cross
• a cue (yellow flash) was presented in advance of the target (blue) which could appear to the right or the eft of the cross
• observers pressed left or right depending on which side the target appeared
• valid cues (80% trials) correctly predicted where target would appear
• they were associated with shorted reaction times, compared to invalid or neutral (no) cue conditions
• conclusion = the cue directs attention to one side and subsequently if the cue is invalid then we have to shift attention to the other side

Question 12

In addition to spatial, what other form of attention is there?

Answer 12

Object-based

Question 13

Discuss Egly, Driver and Rafal

Answer 13

1994

• two objects (rectangles) presented
• one end of an object is cued by brightening it
• if the target (black square) appeared at the cued location, reaction times were faster than if it appeared at the other end of the same object (spatial cuing effect)
• but, responses were even slower if the target appeared on the other object, even through the distance between cue and target was the same for both uncued location
• this shows an object-based biasing of attention

Question 14

What is Treisman’s theory?

Answer 14

The attentional spotlight binds together features that belong together, e.g. are located in same space, to produce a reportable image
These features are initially split and processed in parallel before recombining onto a map which facilitates object perception

Question 15

Discuss how the complexity of attention to multiple features is illustrated by visual search tasks

Answer 15

When a target is defined by a single feature, reaction time is independent of set size. However, when the target is defined by two or more features, reaction time is proportional to set size, This suggests that the attention spotlight has to visit items serially (according to Treisman)

Question 16

What happens when the binding of features in Treisman’s theory fails?

Answer 16

Illusory conjunctions (i.e. when people combine features of two objects into one)

Question 17

When do illusory conjunctions occur in healthy people?

Answer 17

When viewing time is severely restricted

Question 18

When can illusory conjunctions occur with extended free viewing?

Answer 18

Balint’s syndrome

Question 19

Describe Balint’s syndrome

Answer 19

• uncommon
• incompletely understood triad of severe neuropsychological impairments:
  1) inability to percieve the visual fields as a whole (simultanagnosia)
  2) difficulty in fixating the eyes (oculomotor apraxia)
  3) inability to move the hand to a specific object by using vision (optic ataxia)

Question 20

What is Balint’s usually caused by?

Answer 20

Damage to the parieto-occipital lobes on both sides of the brain

Question 21

What does Luria’s observation demonstrate?

Answer 21

Individuals with Balints often report one thing at a time
Observed a patient with Balint’s
A star, drawn in black ink was reported a star
A star drawn froma blue and red triangle was reported as either a blue or red triangle, but never a star

Question 22

What theory rejects the spotlight metaphor for attention? Describe it

Answer 22

Biased competition theory
- suggests attention is a property of mechanisms working to resolve competition for visual processing and behaviour - object based

Question 23

What brain regions are involved in sustained attention?

Answer 23

Right-sided front and parietal regions

Question 24

What is vigilance decrement?

Answer 24

Measure of sustained attention - there is a reduction in ability to sustain attention over time on task

Question 25

Which disorder are sustained attention deficits also present in?

Answer 25

Neglect syndrome

Question 26

fMRI studies show which brain regions to be involved in shifting attention overtly and covertly

Answer 26

superior parietal lobe
intraparietal sulcus
frontal eye fields
- they are symmetrically located in left and right hemisphere
- they have contralateral action (right hemisphere directs attention left etc)

Question 27

What may occur after a right sided parietal lesion?

Answer 27

Left-sided hemineglect syndrome
- if we present a right and left stimulus (which are the same) the patient will report seeing only the stimulus on the right and will have left-sided visual extinction; the covert left attention shift is lost

Question 28

Discuss evidence for executive control

Answer 28

comes from the fact that attention is impaired after frontal lobe injury. Stroop test where subject are required to name the ink colour of a colour word as fast as possible can be used to assess this.
In the incongruent condition, where the ink colour is different to the word, we’re all slowed down to some extent. This is because our pre potent / automatic response is to say the word and we have to inhibit this tendency by exerting control. In this condition there is conflict between what we normally would do and the novel task we’re being asked to perform. Patients with frontal lobe damage may make many errors, actually saying the word instead of naming the ink colour.

Question 29

Disorders of attention may be…

Answer 29

• Developmental – ADHD
• Degenerative – PD and AD
• Young adults – traumatic brain injury, schizophrenia
• Attention lapses – normal, not with brain disorder, particularly under stressful conditions

Question 30

Discuss unilateral neglect

Answer 30

a deficit in attention to and awareness of one side of space
- the neglected object activates the primary visual cortex, even though it is not being perceived

Question 31

What does the house on fire test show?

Answer 31

is subconscious processing of the neglected information: when subjects were presented with two drawings of a house which were very similar but one of them had fire on the neglected side, they reported them as being similar, but when asked where they would like to live, preferentially picked the normal house, rather than the one on fire [80%/20%]

Question 32

Who did the house on fire test experiment and when?

Answer 32

Halligan and Marshall, 1988

Question 33

Therapies for neglect

Answer 33

Therapies for neglect are scarce. Training scanning to the neglected side doesn’t generalize: patients may improve scanning to the left on the training task but not in everyday life. Limb activation and alerting devices designed to cue attention to the neglect size exist but are also of limited use.

Question 34

Define simultanagnosia

Answer 34

inability to perceive more than one object at a time. Overlapping line drawings are used to test for this (e.g. star of David)

Question 35

What did Posner term an ‘extinction-like’ deficit?

Answer 35

contralateral stimulus is ignored in a bilateral test (e.g. in parietal lesions)
It reveals a directional bias when there is competition.
E.g. in a patient with a right parietal lesion, ipsilesional (right) stimulus wins over contralesional (left) one in competition for selection.

Question 36

What is Race theory?

Answer 36

Race theory holds that stimuli are competing for processing power within the brain. Following parietal damage, all contralesional messages are lowered in priority for the brain’s processing in some way – potentially by signal transmission delay – such that when presented with alternative stimuli, the contralesional stimulus doesn’t arrive at the decision center simultaneously with the ipsilesional stimulus, and thus is denied conscious processing.

This deficiency may lead to difficulty on behalf of the patient with processing the stimuli’s 3D position; suggests that there is a more spatial element to attention

Question 37

Bisiach et al

Answer 37

1978
getting patients to imagine the Piazza del Duomo in Milan - ‘Move round’ piazza in their mind and describe scene; Always neglect the left side of what would be seen

Question 38

Kaplan et al

Answer 38

1991
investigated the relationship between distractor extent and neglect, and found a positive correlation between the two. The task he set was to identify all of the letter A’s in a field of letters, with increasing density and distractor numbers (ie. Increased number of non letter A’s).