Vision & Cognition Flashcards
What & Where Pathways
There are two parallel pathways form the primary Visual Cortex (PVC) at the back of the brain to the brain’s processing centers
What Pathways
What pathways use bottom-up processing-looking for features, constructing patterns, and identifying objects.
On the what pathway, we collect information about color, size, depth and motion that tell us what we’re looking at.
Possible Questions: Apple
What is this?
What features tell us what this is?
Where Pathways
Where pathways use top-down, goal-oriented processing concerned with the location and movement of things. It directs the eye asking where something is.
Possible Questions: Grocery store
Where is this?
How do we know?
How do we find the apple? The “Chicken and Egg” Problem
We only know what we’re looking at when we see it so how do we know where to find it? How does your eye pick out the apple when we haven’t processed all of the visual information in front of us? Ware calls this visual search’s “chicken and egg problem
Biased Competition
Prior knowledge influences what we see first. If I’m looking for apples, I will see ‘red’ first
The Absence of Biased Competition
What if I don’t know what I’m looking for but you, the designer, know what you want me to see? You have to know what catches my eye first-what’s the pop out?
Pop Outs
Pop outs are the things that catch our eye regardless of the shapes, patterns and colors in the background
Pop out Features
Pop out features include all of the characteristics being processed in the V1 and V2 regions of the Primary Visual cortex including; color, orientation, size, motion and depth. Most of the time we’re seeing these things without even thinking about it.
“The strongest pop out effects occur when a single target object differs in some feature from all the other objects and where all the other objects are identical, or at least very similar to one another. Visual distinctness has as much to do with the visual characteristics of the environment of an object as the characteristics of the object itself”
Pre-Attentive Features
These are the things we see first based on what we’re looking for. Are you looking for an apple? Then you’ll probably see the color red first among the produce. Research shows that the most obvious pre-attentive features are the ones processed in the Primary Visual Cortex before it hits the What and Where Pathways.
Feature Channels
In the interest of breaking down which features ‘pop out’ of any given image, researcher Ann Treisman coined the term “Feature Channel” to refer to the characteristics of color, orientation, size, motion and depth.
Color Feature Channel
You see the red circle first without even thinking about it
Shape Feature Channel
You see the red circle first without even thing about it, i.e. pre attentively
Multiple Feature Channels
You see the red circle but it takes some time to sort out the multiple channels.
”..the size channel can be used to make a symbol distinct but if the symbol can be made to differ from other symbols in both size and color it will be even more distinct”
“Creating a display containing more than eight to ten independently searchable symbols is probably impossible simple because there are not enough channels available”
Reading Pre-Attentive Features
The presence of a pre-attentive feature is more effective than its absence. Find 3 different objects in each image
The Power of 3
Just like we can only hold 3 visual queries in our head, we can really only distinguish 3 pop-outs in any given image. In other words, we can pick out 3 shapes, sizes, orientations, etc. Anything more than 3 and the pop outs lose their effectiveness.
