Eye Movements and perception

Question 1

Why do we study eye movement

Answer 1

• Shows us where our visual attention is
• Help us understand cognitive processes (reading)

Question 2

Axes, Eye Movement

Answer 2

• Torsion, small and not noticeable
• Horizontal movements, noticeable
• Vertical movements, noticeable

Question 3

Eye movements

Answer 3

Gaze shifting (voluntary):
- Smooth pursuit
- Saccades
- Vergence
Gaze stabilising (involuntary):
- Vestibulo-ocular reflex
- Optokinetic reflex

Question 4

Smooth pursuit

Answer 4

• Helps focus on moving objects
• Our eyes constantly have to make adjustments to see position of the object
• Light from object focusses on the back of the eye

Question 5

Saccades

Answer 5

• Quick movements
• Our eyes will move at the same time and same pattern
• i.e. sat on a train looking out the window

Question 6

Vergence

Answer 6

The movement of our eyes to help focus on objects at varied distances
- Our eyes come together when an object is closer

Question 7

Vestibulo-ocular reflex

Answer 7

• Stabilisation of the eye in space
• They are used to counterbalance motions caused by head and body movement
• Reactions from the inner ear
• Occur when we are walking

Question 8

Optokinetic reflex

Answer 8

• Stabilisation of the eye in visual scene
• Occur when the entire visual field moves
• For example, when in a rotating drum

Question 9

Small eye movements when fixating

Martinez-Conde, S. & Macknik, S. L. (2007)

Answer 9

Microsaccades:
- Minute voluntary movement when fixating

Drifts and Tremor:
- Drifts- Slow movements which occur between microsaccades
- Tremors- small movements back and forth on top of drifts

Question 10

How can you measure eye movements

Answer 10

• Eye tracker
• A camera focuses on the eye so a programme is used to track where the eye moves
• We can look at the pupil position and fixed points on a screen to gather where participants are looking

Question 11

Fixation measures

Answer 11

• We can look at where participants have been looking over a longer period of time
• We can measure the frequency of each fixation
• Duration
• Order of fixation
• A fixation in general

Question 12

Scanpaths

Answer 12

Scanpaths, show fixation patterns
Yarbus, 1967- did this on where we look on faces, eyes and mouth are regions of interest

Question 13

Heatmaps

Mosimann et al. 2004

Answer 13

• It is a colourful map which shows fixation in given areas
• Most fixations are warm colours and least fixations are cool colours
• Control group and Alzheimers group have the same results (fixate in the same place)

Question 14

What is stabilisation

Answer 14

• Some people believe stabilisation is why eye movements occur
• To see an image its vital the back of the eye is stable
• Occurs through VOR and OKR

Question 15

Adapting and Fading

Answer 15

• Troxlers fading is where images fade into the periphery after a while if it is kept fixed on the retina, Troxler (1804)
• some neurons in the retina stop doing their job after a while of looking at the same stimulus

Question 16

The fovea

Answer 16

• Has a lot of photoreceptors
• when looking at a section of an image, for this to be clear, the light from that section has to land on the fovea

Question 17

Why do we not notice eye movements

Answer 17

• motion in the visual scene is not detected
• ‘Saccadic suppression’ (Zuber & Stark, 1966), harder to perceive stimuli when eyes are moving

Question 18

What are some problems with eye movement

Answer 18

• The brain must be able to distinguish between the motion on the retina as a result of eye movements and that caused by objects moving in the environment.
• Can be done by cancelling out signals

Question 18

What are some problems with eye movement

Answer 18

• The brain must be able to distinguish between the motion on the retina as a result of eye movements and that caused by objects moving in the environment.
• Can be done by cancelling out signals

Question 19

Eye movements going wrong

Answer 19

• illusions may occur because we are unable to cancel out eye motions
• In this situation we could be able to see our own eye movements

Question 20

Passive vs active vision

Answer 20

• Passive approach believes that eyes just take information in from the outside world
• Active approach focuses on dynamic processes

Question 21

Combining motor and visual systems

Answer 21

• The areas of the brain which are involved in eye movements are active when eye movements are made as well as visual information being processed

Question 22

Controlling eye movements

Answer 22

• Smooth pursuit has a continuous feedback loop, the positioning of the eye changes depending on where the object is.
• Saccades are fast, the movement is pre programmed

Question 23

Reading

Answer 23

• Eye movements provide evidence that can help us to understand the complex cognitive skill of reading
• We don’t fixate on every word
• Our eyes easily move onto the next line
• Rightward movement

Question 24

Jumbled letters Rawlinson, 1976

Answer 24

• We can read what words say by the first and last letter of the word as we don’t read individual letters we read words as a whole.

Question 25

Link between eye movement and attention

Answer 25

• Can’t process every bit of visual information at once
• Most of the time where we look is where pay attention