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What is bottom up perception?
- Gibson (1966)
- The eyeball sends signals referring to the stimuli viewed to the occipital lobe
- Information then travels through dorsal and ventral streams that deal with (visual and language information) to store this information
What is the fovea?
- Small central pit on the retina composed of tightly packed cones
- Responsible for sharp, central vision
- As many photoreceptors as are found in the rest of the visual field put together
- Must move fovea to get detailed information
- Text and peripheral information can be manipulated when the fovea is not on it and we are unaware of this
What is the blindspot?
- The gap in vision due to the hole in the back of the optic disk the optic nerve goes through
- The brain fills in this gap using other information gained when the fovea scans the environment
What is cognitive impenetrability?
The fact that we are still fooled by things such as optical illusions despite the fact we are aware that they are false
What is feature extraction?
The neural process of making assumptions unconsciously about the environment due to the fact that we do not have enough ganglion cells for all of the receptors in the eye (100,000,000 photoreceptors to 1,000,000 ganglion cells)
What is the waterfall illusion?
- An example of motion aftereffect
- People see motion in the opposite direction on a subsequent image when looking at images moving beforehand
- Baseline activity in neurones is reduced due to stimulation from the illusion, the brain then overcompensates by perceiving upwards movement
What is the Adelson illusion?
- An illusion in which two identical shades of grey appear to be different due to the presence of a shape casting a shadow on the image
- This is because it is surrounded by darker squares on the chess board and so our brains assume it must be above average in brightness
- Our brain ignores the gradual changes in light levels in order to gain an accurate representation of images and so assumes that this is a lighter colour as it is in shadow
What is the flashed face distortion effect?
- When faces are presented at eye level they appear grotesquely distorted if attention is focussed on a point between them
- It is believed that this occurs because each face is perceived in the context of the previous one
- The brain evaluates the difference between the two and the result is a horrifying merging of the two (Tangen, Thompson & Murphy, 2011)
What is the mystery spot?
- An attraction near Santa Cruz in the US
- Weird gravity effects claimed to be due to magnetic reversal (ball rolling up a ramp)
- The house is built at 15 degrees and so our bodies compensate to what our eyes have seen meaning we adjust balance to his
- This is a top down illusion- our environment kids to unconscious inferences that alter how we perceive the stimuli we see (buildings are upright so we must be)
What is pareidolia?
- The phenomenon of interpreting vague and random stimuli as faces
- Hypothesised by Carl Sagan to be an evolutionary trait to allow us to recognise faces from far distances using minimal attentional resources and information
- Allows us to gauge the mental state before anything else allowing us to see if the person means us harm
- (Svobodia, 2007)
What is the hollow face illusion?
- The phenomenon in which a concave mask is interpreted as a convex face
- This is because of top down processing
- There is more information about experiences, past knowledge and what the brain thinks we should see than information that comes in from the eyes
- This distorts our interpretation of things because our brain assumes the mask must be a face, so that's what we think we see (Gregory, 1970)
What are ambiguous perceptions?
- Images or optical illusions that appear in different ways (such as the infamous dress or the coloured face of the cube)
- Gregory (1970) theorises that this is because our brain generates two plausible hypotheses and switches between the two