Motion Perception

First order motion - luminance defined objects changing over time
second order motion - texture or contrast defined objects changing over time

Stimuli undergo objective and continuous spatial displacement

Motion is attributed to stimuli which are physically stationary or in which continuous motion is seen when successive and discrete retinal loci are stimulated
perception of apparent motion is INNATE

ex: stroboscopic movement / phi phenomenon / beta movement

Optimum stroboscopic movement depends upon stimulus parameters
- d is proportional to I, if t is constant- I is inversely proportional to t, if d is constant- d is proportional to t, if I is constant
I = d/t

- fixation on a stationary point of light in darkness, after time it will be seen to move to and fro in the retinal location- depends on shape, size of target, nature of surrounding pattern

- occurs automatically (doesn't require sophisticated thought processes)- young infants can differentiate biological motion form non-biological motion

- optic flow - motion of all the surface elements from the visual world, visual system can determine your current direction of travel from the movement of these surfaces- things in the periphery move fast, while things in the center move slow

- focus - center of the flow

Tau - ratio of retinal image size and rate of change of retinal image size at any time
looming - exponential increase in size of retinal image

- when interval is short, two displays are shown to the same eye

- when interval between displays is long or when displays shown to different eyes

- the ability of an observer to detect details of an object when either the object and/or the person is moving- tests often done with Snellen chart- DVA can equal VA if eye can track target- DVA decreases fast with age- DVA improves form 6-20 then declines

- world drifts up after watching a waterfall