Lecture 3, C 3

Question 1

eye movements are …?

Answer 1

eye movements are the most frequent and fastest of human movements

Question 2

what does “saccadic suppression” refer to?

Answer 2

saccadic suppression: we’re not able to “see” during a saccade

Question 3

name 7 types of eye movements

Answer 3

1. tremor - noise in muscle control
2. dirft - slow movements away from fixation
3. vergence eye movements - binocular focus
4. vestibular ocular reflex - correct for head movements
5. optokinetic reflex - smooth pursuit + saccade
6. smooth pursuit eye movement
7. microsaccades - small eye movements at fixation

Question 4

explain the “active vision” perspective

Answer 4

vision is active:

> movement is essential for vision

> anything we don’t fixate, we miss

> even covert attention is active (microsaccades)

> if we keep image stable, vision fades

Question 5

what drives information processing during visual search

(3)

Answer 5

1. target features (top down)
2. physical salience (bottom up)
3. scene context (learned experience)

Question 6

what kind of words are more often fixated than others?

Answer 6

“content” words are more often fixated than “function” words

Question 7

Reading & eye movements

> how is attention distributed?

Answer 7

distribution of attention is asymmetrical

> 3-4 letters to the left

> 14-15 letters to the right

of fixation

Question 8

text difficulty affects 3 things

Answer 8

text difficulty influences

1. saccade size, decrease with difficulty
2. fixation duration, increase with difficulty
3. regression, frequency increase with difficulty

Question 9

eye tracking: explain spatial resolution

Answer 9

spatial resolution:

> the smallest distance between eye movements that can be detected

Question 10

eye tracking: explain accuracy

Answer 10

eye tracking accuracy

> whether you accurately measure the location the eye is looking at

Question 11

eye tracking: explain precision

Answer 11

eye tracking precision:

> whether you’re consistenly hitting the same spot

Question 12

how long does a period of fixation typically last?

when longer?

associated with?

Answer 12

fixation duration typically between 200 - 250 ms

> longer when viewing scenes, compared to reading

> associated with in depth processing

Question 13

explain the 2 different types of scanning in visual search

Answer 13

1. exploration

> larger amplitude saccades, shorter fixations

2. exploitation

> smaller amplitude saccades, longer fixations