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PERCEPTION AND ACTION ICS 280 Visual Perception Ecological Approach to Perception J J Gibson in 1929 Traditional experiments too constrained Subjects cannot move their heads Study of snapshot vision Perception in its natural environment Emphasizes relationship between perception and movement What is available in environment for perception Slide 2 ICS 280 Visual Perception 1 Beginnings During World War II Pilots ability to land successfully Slide 3 No binocular disparity at that distance No apparent size Characteristics of ground Information provided by the plane s movement ICS 280 Visual Perception Information on Retina vs Environment Slide 4 ICS 280 Visual Perception 2 Ambient Optic Array Ecological optics Description of stimulus based on ambient optic array Ambient Optic Array Structure of the stimulation available at any point in the environment Optic Flow Movement of Ambient Optic Array Slide 5 ICS 280 Visual Perception Optic Flow Effect of movement on optic array Gradient of flow Speed of Flow Focus of expansion Slide 6 Tells where the person is heading to ICS 280 Visual Perception 3 Cues Used Focus of expansion Location Texture gradient Angle Slide 7 ICS 280 Visual Perception Invariant Information Slide 8 Focus of Expansion Texture Gradient Example of checkerboard ICS 280 Visual Perception 4 Visual Control of Action Optic Flow help us Reach destination Maintain balance Anticipating collision Take appropriate actions Slide 9 ICS 280 Visual Perception Judging Destination Just from optical flow Slide 10 ICS 280 Visual Perception 5 Reaching Destination Is optic flow sufficient Yes Do people use flow information Partially Partially other cues Slide 11 ICS 280 Visual Perception Reaching Destination Locomotor flow of line Visual direction strategy Other cues Slide 12 Experiments In dark or snow storm Blind walking experiments ICS 280 Visual Perception 6 Posture or Balance Visual stimulus is critical for balance Standing on one leg experiment Maintaining posture Swinging room expriment Children fell Adults acted like puppets Ripley s Believe It or Not Slide 13 ICS 280 Visual Perception Anticipating Collision Direction of View Bearing Estimating object s distance and speed Tau strategy Size of object in different pictures Rate of expansion of object s edges Visual cues for gymnasts Slide 14 ICS 280 Visual Perception 7 Neural Mechanisms Collision sensitive neurons in pigeons Neurons in medial superior temporal MST One kind fires with expanding stimulus Other fires with circular movement Slide 15 ICS 280 Visual Perception Does flow information affect neurons MST responds to large receptive fields Perception flow summates over a large area of the visual field Slide 16 Spatial summation experiment ICS 280 Visual Perception 8 Slant based on Potential for Action Subjects asked to estimate the slant of a hill Verbal Visual Haptic Verbal and visual Overestimated Depends on the hardness of the task of climbing it Depends on the physical condition of the subject Haptic Slide 17 Correct estimation Helps to do job with maximum efficiency ICS 280 Visual Perception Perception meets the Motor System Slide 18 ICS 280 Visual Perception 9 Important Parts Anterior inter parietal area AIP Pre motor area PM Motor area MI Slide 19 ICS 280 Visual Perception Anterior Inter parietal Area AIP Motor dominant neurons Visual dominant neurons Responds to vision only Visual and motor neurons Responds to action only Responds to both Located between the vision and the motor area Slide 20 ICS 280 Visual Perception 10 Pre motor Area PM Mirror Neurons What are these for Slide 21 Monkey grasps an object Looks at another person grasping an object Not to a pair of pliers grasping an object Understand motor actions and react to them Mimic actions ICS 280 Visual Perception Mirror Neurons in Humans Responds to observation action and imitation Maximum during imitation Slide 22 ICS 280 Visual Perception 11 Action Hearing and Vision Sound cues are very important Gymnasts McGurk Effect Different perception based on Only speech Both vision and speech Slide 23 ICS 280 Visual Perception 12


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UCI ICS 280 - PERCEPTION AND ACTION

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