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| Question | Answer |
| why is motion important? | evolutionary importance for survival + indicates life |
| what does motion imply about objects? | that they are alive -- inanimate objects cant move |
| what are the functions of motion? | breaks camouflage, helps segregate figure from ground + perceptual organisation, allow to actively interact with environment, our direction, collisons, time of, etc. |
| movement attracts our.. | attention |
| the movement of an object relatuve to the observer provides us.. | information about the 3D shape |
| what does the random dot kinetogram suggest | we can't perceive & track edges & contours of one object against another |
| what's the name for this problem? define it | correspondence problem -- motion detection is direct & can't imagine a visual system that matches point for point over time |
| what are the 5 ways to make light move/types of motion? | real motion, apparent motion, induced motion, autokinetic motion, movement after-effects |
| what is real motion | where light physically moves, displaced from one point to another |
| when is it perceived? (in terms of our eyes/) | when the eyes are stationary -- so that the image moves across the retina |
| what does the movement of an image across the retina elicit again? | neurons in the visual system respond & fire away action potentials |
| what particular part of a stimulus/light's movement is when the receptors respond best? | when they move in a particular/preferred direction + tuned to it |
| how can we change the tune for speed in the receptors in the motion-detection systems? | introducing delays or change how widely spaced photoreceptors are in system |
| whats the aperture problem? | where, because we see thru tiny lil windows all the time, there's ambiguity in what's being perceived |
| whats the solution/result of this? | output of all detectors must be combined & integrated at some stage |
| where does this occur? | medial/middle temporal area |
| which animals were these experiments conducted on? middle temporal area receptors | monkeys |
| what did they find? | as correlated movement of random dots increased, so did the firing of neurons in MT |
| what was further evidence for this? | when the neurons in the monkeys' MT were excited with zero visual stimuli, but monkeys pressed the 'up' button |
| what are the thresholds for detecting real movement? | no strict threshold -- its dependent on the background, smth about 1/6th to 1/3rd of a degree of visual angle |
| what is the perception of velocity affected by? | environment & size of it + moving object e.g. a cat has to move twice as fast to appear to be moving at the same speed as a mouse |
| what are some parts of motoin detection that were difficult to explain? | -> no movement on retina, but motion detected -> movement on retina, but motion not detected |
| which theory helped address this? | helmoholtz' outflow theory aka. corollary discharge theory |
| what is the idea of the theory? | if the movement of eye-muscle command from brain (output) & the signal of motion/no-motion from visual image on retina (input) are different = motion perceived |
| whats an example? | when tracking a car, eyes move but retinal signal remains stationary, therefore we perceive movement of the car |
| state the evidence that supported helmholtz's theory | -> afterimages move when we move our eye -> world moves when we passively wobble our eye -> paralysed eyes attempting to move led to apparent movement |
| what is apparent motion | illusion of movement between two lights flashing on & off at certain speeds |
| whats another name for this movement/effect? | stroboscopic movement |
| table of movements/ speeds and their effects | *<30msec: no (simultaneous) *30 - 60 msec: partial movement *60 msec: optimal *60-200msec: beta & phi movement *>200msec: no (successive) |
| what is the beta & phi phenomenon? | beta: movement appears to occur between lights but difficult to perceive moving object phi: perceive an object between |
| slow apparent movement can be... | ambiguous |
| as distance of lights in apparent motion increases, what must we do to maintain same perception of movement? | either the time interval or intensity of flashes must also increase |
| what is induced movement? | where the object isn't moving but the background is |
| autokinetic movement | self-moving [For example, if we turn off all room lights and flash a singular light around — when the surrounding framework of the room is not visible, the small stationary light appears to move, usually in an erratic path] |
| what famous study was autokinetic motion seen in? | Sherif's conformity study |
| what are motion after-effects | when perceiving motion after perceiving motion |
| example | waterfall illusion -- direction of after-effects motion is dependent on motion of stripes across the retina |
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