Visual Attention 1

Arash Afraz

“Visual Selection” might be a better term

Do we really see without attention?

• Inattention Paradigms

• Attentional Blink

• Change Blindness

• Intentionally Ignored Information

Change Blindness

Change Blindness

Hey Arash don’t forget more demos!

What we

think we see!

What we really see!

Visual Attention (selection)

• Overt Visual Attention (eye movements)

• Covert Visual Attention

Eye Movements

1. Physiological Nystagmus

2. Saccadic Eye Movements

3. Smooth Pursuit

4. Vergence Movements

5. Vestibular Movements

6. Optokinetic Movements

Physiological Nystagmus

• Preventing from stabilizing the image

• Random walk movements

Physiological Nystagmus

Saccadic Eye Movements

• Very Rapid (150-200ms planning and action) (900 degree per second)

• Ballistic Movements

Saccadic Eye Movements

Saccadic Eye Movements Saccadic Suppression

• Motion Blur Problem

• “Too Fast Motion” explanation!

• “Visual Masking” explanation

• Is it a real problem!?

Smooth Pursuit

• Slower Than Saccade (100 degree per sec at maximum)

• Smooth (not jerky)

• Feedback (not ballistic)

• Acuity (importance of smooth pursuit in biology)

Vergence Movements

• Slow (10 degree per Sec)

• Diconjugate

Vestibular Movements

• Head is not still!

• Faster than pursuit

• Mostly unconscious

• Controlled by vestibular system

Optokinetic Movements

• Involuntary tracking of large field movements

• Bi-phasic (slow-fast)

• Vertigo!

Contextual Effects in

Eye Movements

Covert Visual Attention…

• How to select target of next saccade?

• There are some social conditions in which we can’t shift our attention overtly

• Attending to more than one item

To be continued!