Active vision

Question 1

What is meant by passive vision?

Answer 1

Vision in the absence of eye movement

Question 2

What are the underlying assumptions of psychophysics?

Answer 2

There is a threshold below which no sensation present

Orderly relationship between stimulus intensity and sensation level

Question 3

What did Posner do?

Answer 3

Used precueing to determine whether attention to a specific location improves the ability to respond rapidly to a stimulus presented at that location

Question 4

What types of cues did Posner use?

Answer 4

Central - Fixate on the central spot and see an arrow that shifts covert attention to the expected side
Peripheral - luminance in peripheral vision leading to automatic shift of covert attention

Question 5

What was Posner’s spotlight metaphor?

Answer 5

Visual attention like a spotlight traversing the visual field and illuminating regions of interest (all while eyes fixated on one spot)
The spotlight is our covert attention

Question 6

What is the difference between endogenous and exogenous attention?

Answer 6

Endo = attention generated voluntarily e.g. by the central cues 
Exo = attention "captured" by peripheral visual events

Question 7

Why is action of covert attention important?

Answer 7

Speeds simple reaction times and improves perceptual discrimination ability

Question 8

What is inattentional blindness?

Answer 8

Failure to perceive a stimulus right in full view simply because it is not attended to

Question 9

What is the distinction between saccades and fixations?

Answer 9

Saccades are accurate and high velocity eye movements

Fixations are when the eye is very still but small movements can occur e.g. tremor, drift and microsaccade

Question 10

How do we get the impression of the world around us being a continuous scene?

Answer 10

Collect series of visually detailed “snapshots” in a visual scene and the brain combines these into a whole image

Question 11

What was the case of AI?

Answer 11

Gilchrist, Brown an Findlay

Girl unable to make eye movements but used her head movement in exactly the same way (just a few seconds slower)

Question 12

What did Gilchrist and Findlay suggest in 2003 regarding covert attention?

Answer 12

Covert attention shifts are slow
Covert sequential scanning doesn’t normally occur during fixations
Covert attention shifts can programme eye movements though

Question 13

What eye movements are involved prior to performing an action?

Answer 13

Location - find the object to use
Direction - fixate on the object
Guide - bring 2 objects together
Check

Question 14

What is a real-life important example of coordinating vision and action?

Answer 14

Driving around a corner - we focus on the tangent point on the inside of the road curve
Implications for positioning road signs

Question 15

What is change blindness?

Answer 15

Failure to notice appearance/disappearance of something when separated scenes using black mask - this is a capacity limitation rather than a visual limitation

Question 16

What is meant by inhibition of return?

Answer 16

Processing cost in terms of reaction time with returning to a non-cued location - spotlight has already shifted elsewhere

Question 17

What does visual search involve?

Answer 17

Combination of bottom-up (perceptual) searching and top-down (goal-driven, target in mind to match to)

Question 18

What is meant by object-based non-spatial attention?

Answer 18

2 objects transparently superimposed in same place
Attended object linked to greater BOLD response in brain region specialised to respond to that particular type of visual stimulus
2 different brain areas activated even though objects in same location

Question 19

What is the attentional blink?

Answer 19

Inability to report target if appears too soon after initial stimulus because initial stimulus takes over limited attentional capacity

Question 20

What 4 characteristics determine our fixations?

Answer 20

Stimulus saliency, knowledge about scenes (which affects expectations), nature of task, and learning from experience (where should we look for something)

Question 21

What findings followed on from Posner’s research?

Answer 21

When attention is directed to an object, the enhancing effect of attention spreads through the object e.g. if cue top of an object, but target appears at bottom responses faster than if target appears in separate adjacent object
Effect remains even if initial shape partially obscured - still perceive it as a whole object

Question 22

What did Carrasco suggest regarding attention’s enhancing capabilities?

Answer 22

Able to enhance appearance of an object and alter our perception - difference in contrast between gratings
If identical but one preceded by attention-capturing dot, perceive that one as higher contrast and most visible

Question 23

Distinguish between pre-attentive processing, covert and overt attention

Answer 23

Pre-attentive processing = parallel processing regardless of attentional resources
Overt attention = high resolution, at eye fixation. Covert attention = may be in a different location to eye fixation, cued endogenously/exogenously (slow, covert sequential scanning does not normally occur during fixations, and shifts are linked to eye movements)