Eye Tracking - Movements

Question 1

what are covert and overt attention?

Answer 1

using movements of attention ‘mind’s eye’ and using movements of the eye

Question 2

Programming an eye movement involves the allocation …. of….

Answer 2

attention to the object in advance of the movement itself

Question 3

therefore, covert attention moves

Answer 3

prior to eye movements

Question 4

Using attention we can focus on

Answer 4

properties (e.g. colours) and objects

Question 5

however using the eyes, we can

Answer 5

only focus on locations

Question 6

Attention starts to move …

Answer 6

faster than the eyes

Question 7

which theory described this “The eyes usually follow where attention leads”

Answer 7

(pre-motor theory)

Question 8

Focused attention may be necessary for…

Answer 8

even a clearly visible stimulus to be consolidated into visual short-term memory (VSTM) and for it to become available for conscious report

Question 9

Attention has a dwell time somewhere in the region of

Answer 9

200 ms to 250 ms

Question 10

how long does it take to plan and execute a saccade?

Answer 10

150 ms and 200 ms to plan and execute

Question 11

of which only …

Answer 11

30 ms is required to actually shift the eyes to a new fixation location

Question 12

Why don’t we see a blur when our eye is speeding to a new location?

Answer 12

Saccadic suppression, perhaps due to visual masking from sharp fixated images

Question 13

As our attention hops around a scene, with the eyes saccading in tow, how is the information that we extract put back together again to form a single representation of the scene we are studying?

Answer 13

short : we dont know

The spatiotopic fusion hypothesis? (just says binds them back together again

Question 14

what is smooth persuit ?

Answer 14

eye movements track a moving object to keep it in foveal vision when the head is still (areas MT and MST project to the brain-stem gaze centres – when these areas are lesioned a moving object appears to jump forward in a blur)

schizo issue (extra)

Question 15

what are Vestibular and optokinetic movements ?

Answer 15

work to keep a moving image in foveal vision when the head moves (vestibular inputs from the inner ear and visual inputs from MT and MST converge on the vestibular nuclei adjacent to the gaze centres)

Question 16

Eye tracking research has traditionally focused on

Answer 16

stationary observers viewing stationary scenes

Question 17

The newer eye-trackers have

Answer 17

head cameras as well as eye cameras so that eye movements that maintain fixation on a target object in a scene during a head movement are not recorded as movements of the eyes (in the scene)

Question 18

what is an unavoidable eye movement?

Answer 18

a tremor in the eye muscles called (physiological nystagmus)?

Question 19

if surpressed chemically or through ‘stabilising’ an image on the retina, what happens?

Answer 19

the image completely disappears in seconds

Question 20

Eye link technology comes in either …

Answer 20

binocular or monocular

Question 21

the sampling rate is

Answer 21

250 / 500Hz

Question 22

how accurate is the gaze position ?

Answer 22

Accurate – Average gaze position error<0.5°.

Question 23

eye trackers can also eithe track your xxxx or not

Answer 23

•Head

Question 24

and the data is in….

Answer 24

•Real-time data access on-line analysis of data (saccade, fixations, blinks)

Question 25

eye-tracking setup procedure: 5 steps

Answer 25

1) Head band setup
2) Calibrate camera position
3) focus camera
4) thresholding the camera
5) adjust the head camera

Question 26

first,

Answer 26

first set up the head band equipment - on head

Question 27

then

Answer 27

calibrate camera position

Question 28

then

Answer 28

focus camera

Question 29

then

Answer 29

Thresholding the Cameras

Question 30

two ways to Threshold the Cameras?

Answer 30

The pupil threshold can be adjusted automatically, through the Auto- threshold command, or manually, through the up/down arrow.

Question 31

two extreme outcomes to threshold miscalculation?

Answer 31

A threshold too low will result in shadows (fig.1), while a threshold too high will result in a noisy signal (fig. 2)

Question 32

what is drift correction?

Answer 32

A drift correct needs to appear before each trial. It corrects for the amount of drift occurring between trials.

The drift correct is similar to the dots you use for calibration, and the participant needs to fixate it before the trial begins.

The tracker can use this dot to correct for small drifts in the calculation of gaze position.

A drift correction, therefore, can be used for two purposes:

1) It can be a test to confirm whether the calibration is still valid – you cannot run the trial without completing a drift correct successfully, it will not trigger if the participants’ eye is not on the drift correct.
2) It can function as a “fixation dot” (more commonly seen in non-eye tracking research as a cross) for the participant to look at so that they always start the trial in the same place (the centre).