6. Failures of Vision Flashcards
What is illusory motion?
The illusion that a static image is moving caused by eye movements.
What is the interpretation of colour illusion?
The same colour can appear different depending on the surrounding colours.
What is the colour after-effect
Due to colour opponency whereby the photoreceptors (rod cells) inhibit the opposite colour. There is red-green opponency and yellow-blue openency (actually red/green and blue as there is no yellow rod cell). So the neurones responding to red will inhibit green and as there is slow adaptation when the constant red stimulus is removed it will be perceived as less red and therefore more green.
What is the colour after-effect
Due to colour opponency whereby the photoreceptors (rod cells) inhibit the opposite colour. There is red-green opponency and yellow-blue opponency (actually red/green and blue as there is no yellow rod cell). So the neurones responding to red will inhibit green and as there is slow adaptation when the constant red stimulus is removed it will be perceived as less red and therefore more green.
What is the colour after-effect
Due to colour opponency whereby the photoreceptors (rod cells) inhibit the opposite colour. There is red-green opponency and yellow-blue opponency (actually red/green and blue as there is no yellow rod cell). So the neurones responding to red will inhibit green and as there is slow adaptation when the constant red stimulus is removed it will be perceived as less red and therefore more green.
What is motion-induced blindness?
When a static object surrounded by moving objects appear to disappear.
What factors increase motion-induced blindness?
- High contrasted object
- Small target size
- Slow target speed
- No target flicker or a fast target flicker (U relationship)
Describe interpretation of binocular views
When the two views from each eye vary the brain interprets them as coming from a 3D scene.
What is motion-induced blindness?
When a static object surrounded by moving objects appear to disappear. Suggests that the visual system shifts between objects, perceiving them one at a time and attention can’t be divided between two unfused elements.
Describe interpretation of binocular views
When the two views from each eye vary the brain interprets them as coming from a 3D scene.
What are some pictorial / monocular cues?
Linear perspective, size of familiar objects, occlusion, shadows, aerial perspective and height in field. These cues are only correct from one vantage point so are therefore called monocular cues.
Describe the illusions in the Ames room
- The room appears cuboidal when it’s called a trapeze.
- Assumption of parallel lines when they are actually converging.
- Assumption of a constant horizontal floor gives the illusion of the back wall of the room being at a constant distance from the vantage point when, actually, the left corner is further back.
- Floor slopes, oddly shaped tiles, walls don’t meet at 90 degree angles.
- Actual size and retinal image size of familar items, such as the clock, are used to estimate the distance from the person and clock.
What is binocular disparity?
The brain has to work out the cause of the retinal image produced from two vantage points which can lead to errors, such as the convergence problem whereby the brain assumes the two rays came from the same object.
