PERCEIVING MOVEMENT ICS 280 Visual Perception Ways to create movement Perception More than one ways to create the sense of movement Slide 2 Real movement is only one of them ICS 280 Visual Perception 1 Important for survival Animals become still when they sense danger Many animals have poor depth perception pigeon and color vision cats and dogs They will be detected if they move None lack the ability to perceive depth Important for survival Slide 3 Motion agnosia Can t even pour tea follow conversations ICS 280 Visual Perception Real Movement Movement is not the only criteria for detecting Movement detected if the object covers about 1 6 degree of visual angle per second Changes to 1 60 degree per second with the addition of the bars Slide 4 ICS 280 Visual Perception 2 Apparent Movement Inter stimulus Interval Inter stimulus spacing Intensity Illusion Slide 5 Perceive movement when it is not there ICS 280 Visual Perception Induced Movement Motion of one object induced by movement of another Slide 6 Moon racing through clouds on a windy day Sitting in the car and the adjacent car moves out ICS 280 Visual Perception 3 Movement Aftereffct Waterfall illusion Spiral motion illusion Slide 7 ICS 280 Visual Perception Direction specific Movement Perception by Feature Detectors Directionally Selective Neural Circuit Slide 8 ICS 280 Visual Perception 4 Further Up in the MT Experiment with the monkey VERY close relationship between MT neurons firing and monkey s behavior Increased with increase in correlation May be the sole neurons that are responsible Very few neurons in a small region May be approaching specificity coding Slide 9 ICS 280 Visual Perception Is movement of the image sufficient Perception does not depend only o Simage on the retina How do we track moving objects Image stays at the same retinal location How do we see stationary scenes as stationary Slide 10 Eye moves Retinal image moves ICS 280 Visual Perception 5 Corollary Discharge Theory Movement perception depends on Corollary discharge signal Image movement signal Comparator circuit Exclusive OR Slide 11 ICS 280 Visual Perception Testing the Theory Movement of afterimage in the dark room By moving your eye afterimage is always at same location in the retina Moving the eyeball Following a flying bird Physiological evidence Slide 12 Real movement cells ICS 280 Visual Perception 6 Optic Array How things move relative to one another Optic Array Structure created by the whole scene its color and textures Local change in optic array Object moves relative to other Covering and uncovering stationary background Even for a moving object the background content on retina changes Global change Observer is moving Slide 13 ICS 280 Visual Perception Optic Array Slide 14 ICS 280 Visual Perception 7 Perceptual Organization Law of Common Fate Perceiving a camouflaged bird Slide 15 ICS 280 Visual Perception Perceptual Organization Point light walkers Slide 16 Movement helps detect a person ICS 280 Visual Perception 8 Perceptual Organization Kinetic depth effect Moving of 2D object shadow perceived as a 3D object Motion can create the sense of depth on 2D surface Slide 17 ICS 280 Visual Perception Perceptual Organization Motion capture Slide 18 Elements contained in a figure tend to move with the figure ICS 280 Visual Perception 9 Role of Intelligence Movement perception depends on smallest change Occlusion Meaning Slide 19 Face rotation experiment Shortest path constraint Special sensitivity to human form ICS 280 Visual Perception Movement in same direction Slide 20 ICS 280 Visual Perception 10 Occlusion Moving object will cover and uncover background When background is covered it still exists Slide 21 ICS 280 Visual Perception Occlusion Slide 22 ICS 280 Visual Perception 11 Meaning Slide 23 ICS 280 Visual Perception Knowledge Slide 24 ICS 280 Visual Perception 12