Psyc351Week9

Slide2 : Motion and Event Perception Functional Utility: Gordon Walls quote Updating location Figure-ground, edge detection, grouping Recognizing objects and actions from motion: camouflage


The Problem : The Problem Perceived motion is independent of retinal motion; the latter is neither necessary nor sufficient for the former to occur. Does this sound familiar? Cf. perceived brightness is independent of retinal illumination, etc.


Nine stimuli that producethe perception of motion : “Real” motion Stroboscopic (apparent) motion: beta, phi, etc. Induced motion Autokinetic motion Motion aftereffect (‘waterfall illusion’) (second site) Fooling the corollary discharge system Wave motion Spatial distortions (e.g., dot on Muller Lyer illusion – Colin Bauer) Other: op art, Ouche illusion, illusory rotation another, yet another, blurred, minimal, also, check Akiyoshi's site Nine stimuli that produce the perception of motion


Nine stimuli that producethe perception of motion : “Real” motion Nine stimuli that produce the perception of motion Problem 1: real motion cannot be generated via PowerPoint on a computer screen Problem 2: real motion can be seen without retinal motion


9 stimuli that produce motion perception : “Real” motion Stroboscopic (apparent) motion: beta, phi, etc. 9 stimuli that produce motion perception


Stroboscopic (apparent) motion:Beta motion : Stroboscopic (apparent) motion: Beta motion


Nine stimuli that producethe perception of motion : “Real” motion Stroboscopic (apparent) motion: beta, phi, etc. Induced motion Autokinetic motion Motion aftereffect (‘waterfall illusion’) (second site) Fooling the corollary discharge system Wave motion Spatial distortions (e.g., dot on Muller Lyer illusion – Colin Bauer) Other: op art, Ouche illusion, illusory rotation another, yet another, blurred, minimal, also, check Akiyoshi's site Nine stimuli that produce the perception of motion


Motion detection circuit(Reichardt Detector) : Basic network with asymmetric timing delay Can explain real and beta apparent motion Also: can add opponent process mechanism Detection of velocity: univariance problem cross-fiber comparisons Motion detection circuit (Reichardt Detector)


Complications : The Correspondence Problem: what goes with what? The Aperture Problem (“Barber Pole”, Hans Wallach) Which way did they go? Ambiguous beta motion Motion of subjective contours Complications


Random Dot Kinetogram (video) : Random Dot Kinetogram (video)


Structure from motion : Grouping: Glass patterns; common fate; cube Johansson’s point-light walkers: (static, animated) Rigidity principle: two lights moving in square path Kinetic depth effect Duncker’s wheel, common vs. relative motion Other unusual cases of motion perception: Rubber pencil illusion breathing square gelatinous ellipses with and without surround (Ted Adelson’s site at MIT) Structure from motion


Evidence on motion perception systems : Animal data: tuning curves for cortical cells, selective adaptation Looming detectors Selective adaptation thresholds measured psychophysically Motion aftereffect: suggests opponent process system Evidence on motion perception systems


Slide14 : “Direct” perception of motion: impending collision, time of arrival


Slide15 : “Direct” perception of motion: Focus of Expansion


Slide16 : Miscellaneous: Apparent motion: Phi and Beta Exner’s two flashes Wertheimer, Korte Ternus phenomenon (short, long ISI, displaced) Kolers/Pomerantz motion Short-range system: motion before form Long-range system: form before motion Ramped vs. Abrupt onsets and offsets Motion from any progressive change: waves, traffic flow


Dynamic Mental Representation (Freyd) : Dynamic Mental Representation (Freyd) Memory representations for moving (dynamic) images Present a sequence of images of an object in motion Then test for memory for the last item in the sequence People’s memory will extrapolate and reconstruct a memory going beyond the last image actually presented.