L6 - Perception (to do) Flashcards
What two phases are needed for using visual information for action?
Planning phase
Guiding phase
What did Kowler & McKee (1987) find in their visual information experiment?
That visual information (e.g. target location, speed) is used to plan and guide eye movements
What is a “smooth pursuit eye movement”?
The eye movement you make when tracking an object
What are involved when “planning a reach”?
- Reaches are planned in eye-centred coordinates
* Suggests visual localisation reference framework is important when making a hand movement (if goal directed you are using this eye-centered coordinate as a reference frame to help you find where this thing is in space)* - Reaches are planned using re-mapped target locations
* Re-mapping occurs when you make an eye-movement* -
Eye and hand movements are planned with respect to a common framework
* You use the same framework when you update your movements when you interact with your environments*
Using eye-tracking software while doing everyday tasks, what did Land, Mennie and Rusted (1999) discover?
The eye and the hand movements were quite co-ordinated, more than originally thought.
People put their hands where their eyes had been.
What is a “saccade”
Eye movement characterised by rapid acceleration to new location
What does a saccade allow us to do?
Allows us to foveate points of interest
What are smooth pursuit eye movements characterised by?
A constant velocity once at the same speed as target
What do smooth pursuit eye movements allow us to do?
Allows us to track an item of interest
(often seen with a saccade)
How often are saccades made?
3 times a second
Is the visual information we use to make perceptual judgements the same as the visual information we use to make smooth pursuit eye movements and saccades?
Yes
Similar visual information is used to guide eye movements and make perceptual judgements
Saccade movements are changed by the quality of the information.
What does this suggest?
You are using the visual information to program and control that eye movements
Eye movements are more variable when visual information is ___
What does this suggests
Visual information is poor
Suggests that the variability of the eye signal is comparable to the visual signal, which means they are using a common signal
Eye movements and hand movements have a _____ signal
common signal
What happened in the Pellison et al (1986) and Henriques et al (1996) experiments when they measured the accuracy of pointing performance when altering the direction of their gaze?
Accuracy was decreased when direction of gaze was not in the same direction they were asked to point
What do we use to plan a “sequence of slow guided movements” (e.g. moving our hand around a table to make a sandwich) (Hayhoe, 2000)
“Look ahead Saccades”
Our saccades are used to gather information regarding what our hands are about to do next
Saccades are used as an _______ gathering device
information
Which area of the eye is most high resolution?
Fovea
Why do we need to make so many Saccades?
Because we have low amounts of visual acuity in our peripheral vision,
We need to constantly refocus our eyes to gather accurate information
You know from experience that the world is high resolution across the visual field.
True or false
False
Visual resolution varies across the visual field
Do we make our saccade movements randomly or do we have a strategy?
We use saccades strategically - Yarbus (1967)
How did Yarbus (1967) show that we use saccades strategically?
Asked people to view a picture in 5 different ways and measured their saccade movements.
Saccades differed depending on the goals of the viewer
Saccades are random
True or false
False
Saccades are NOT random (Yarbus 1967)
What is “saccade latency”
The time between when the stimulus appears and when your eyes move
How long is the saccade latency?
150ms-200ms
How long does a saccade take? (How long is it “in flight”)
20-50ms depending on the length the eye has to travel
Including all stages of the saccade, roughly how long does it take?
300ms
What did this Renniger, Coughlan, Verghese & Malik (2005) experiment reveal about the nature of how people use saccades?
That we use information to maximise the amount of new information about an object
How did Renniger, Coughlan, Verghese & Malik (2005) determine that each eye movement maximises the amoutn of new info on the object?
They would move their eye movements to where the object is “changing” or different.
Where the curviture changes and there are new features.
The ____ saccades you do, the ______ your ______ of a scene is.
1) more
2) greater
3) memory
The more saccades you do, the greater your memory of a scene is.
What are 3 reasons why you would move your eyes?
- Limited spatial resolution in the periphery
- Shifting the eyes shifts the fovea to get a higher resolution info about the environment
- Gather information for perception and action
Why is it important to coordinate the eye and hand?
Goals are usually visually defined
- Visual info about target location*
- Visual feedback about hand position (relative to target)*
- If you co-ordinate eye and hand you get more information*
What is a corollary discharge?
When you make a movement you get a proprioceptive feedback from the muscles that says “I made that movement” - this is corollary discharge
What relationship does corollary discharge have with the eyes and with the hands?
It’s associated with eye movement
Aids guidance of hand movement
Are people better at finding a target with their hands if they -
Are in a light room but can’t make a saccade
Are allowed to use a visual saccade but in the dark
Why
Allowed to use a visual saccade but in the dark
The corollary discharge from the eye movement helps guide the hand movement
During rapid pointing
The ____ typically leads the hand
The eye typically leads the hand
Eye and hand movements are ususally ______ and ______ correlated
Temporally and spatially
Eye and hand movements are ususally temporally and spatially correlated
What part of the brain is responsible for target selection?
Superior colliculus
How did McPeek and Keller (2005) determine what part of the brain is responsible for target selection
When administering a drug to the superior colliculus that deactivated it, participants were no longer able to find new targets
Visual processing pathway -
Retina - _______ - Pulvinar - Parietal cortex
What is missing?
Superior Colliculus
What did Moore and Fallah (2004) find in regards to attention and eye movement?
There are some shared mechanisms for deploying attention and making an eye movement.
One a decision is made and a saccade is “in flight” there are no new decisions to be made
True or False
False
There is a complex circuit and decisions are constantly being made (e.g. where you are going next)
Describe the Itti & Koch (2001) model.
- You have scene info around you (vis info)
- Info gets fed to Inferotemporal or posterior parietal cortex
- Info goes to prefrontal cortex
- Info goes to motor systems + memory and cognition - superior colliculus
- Superior colliculus leads to eye movement
What is the prefrontal cortex involved in?
(involved in inhibition of responses/decision making)
____ information is used to guide eye and hand movements
visual
Two common types of eye movements are
saccades and smooth pursuit
Eye and hand movements are often _______
co-ordinated
Eye movements and the deployment of attention can be..
related
Exam prep notes last slide
Use lecture summaries and SDLs as a study guide
Practice exam questions on canvas
Good luck!
