Lecture 13 - How the brain creates perceptions, illusions and hallucinations Flashcards
Describe Ames’ window illusion.
It was the rotating door in that video.
The brain is trying to do ‘shape constancy’.
What is perception?
Perception isn’t seeing an “image” (a “picture”).
Perception is interpretation
Scene interpretation, object recognition, face recognition, word recognition.
It happens automatically once your brains learnt.
But also,
Perceptual filling in… so perception is created within the brain (as part of interpretation)
What are illusions?
Illusions are the brain’s interpretation of confusing sensory signals.
They reveal the clever things our brains do during the everyday perception we take for granted. They reveal the inner workings of the system we normally have no awareness of.
They are rare in real life.
What is the moon illusion?
The moon looks bigger near the horizon, but its size has not changed…
What is the depth illusion?
Perceived size depends on perceived distance and on the size of nearby objects
Your brain has learnt that small stimuli far away are actually large objects, while big stimuli close by are actually small objects.
What is lottos cubes?
Colour depends on perceived lighting, shape and shadow.
Colour takes into account its environment.
(the yellow and purple cubes making the grey square different colours)
The firing rate of cones in our eye tells us what ____ an object is.
The firing rate of these cones tells us what colour an object is.
In our eyes there are three types of ‘cone’ light receptors.
They are activated by different wavelengths of visible light: long wavelengths (L cone), middle wavelengths (M cone), short wavelengths (S cone).
Colour is indicated by the comparison of activity between these types of cone.
(look at slides 33-34 in relevant powerpoint to see how cones exactly work)
Describe Van Lier’s Stars.
http://illusionoftheyear.com/cat/author/rob-van-lier/
How are faces perceived?
Recognising Faces:
Faces are perceived (i.e. automatically interpreted) relative to their context and your lifetime of experience
Face perception is based on comparison – locally, with context, with what you’ve seen before.
This achieves some computationally complex interpretations; Face recognition is a very difficult processing problem
(computers are bad at it, and so are we sometimes)
Thus, face perception is a creative process based on what’s already in your brains as well as the incoming (sometimes ambiguous) signals…
READ CHAPT 5 (senses) 6th ed.
(make notes if you want or just teach yourself on whiteboard.)
READ CHAPT 6 (perception) 6th ed.
(make notes if you want or just teach yourself on whiteboard.)
READ CHAPT 3 (evolution and natural selection, ignore stuff bout genetics) 6th ed.
(make notes if you want or just teach yourself on whiteboard.)
READ CHAPT 4 (neurones and drugs, ignore stuff on brain imaging) 6th ed.
(make notes if you want or just teach yourself on whiteboard.)
