1Sensation & Perception• Ch. 8-13: Review© Takashi Yamauchi (Dept. of Psychology, Texas A&M University)Depth and size• Monocular depth cues• Binocular depth cuesMonocular pictorial cues• Occlusion• Relative height• Relative size• Familiar size• Atmospheric perspective• Linear perspectiveLeonardo da Vinci (1452-1519)There has never been an artist who was more fittingly, and without qualification, described as a genius. Like Shakespeare, Leonardo were from an insignificant background and rose to universal acclaim. Leonardo was the illegitimate son of a local lawyer in the small town of Vinci in the Tuscan region….Mona Lisa (1503)The Dreyfus Madonna: da Vinci 1469The Santa TrinitaMadonna: Cimabue (1260/80)2Linear perspectiveThings get smaller when they are away.OcclusionRelative heightRelative sizeAtmospheric perspective3Texture gradient• Two types of perspectives– Linear perspective– Atmospheric perspectiveBelvedere: Escher4Binocular depth cues• Ever visited an IMAX theater?• Or some special planetarium?– Wearing special sunglasses and see a large screen.– You get an incredible 3-D effect.Binocular disparity• The binocular disparity arises when a given point in the external world does not project to the corresponding points on the left and right retinae– (Palmer, 1999, “Vision Science”)Binocular disparity• Your two eyes are getting different images  disparity  double imagesCorresponding pointsCorresponding pointsNo disparity disparity5Small disparityLarge disparity No disparityHoropter (Vieth-Muller circle)Small disparitylarge disparitysmall distancelargedistanceSensation & PerceptionCh. 9: Perceiving Movement© Takashi Yamauchi (Dept. of Psychology, Texas A&M University)Main topicsThe functions of motion perceptionThe direction of movement4 different ways to create the perception of movement• Real movement– The object is physically moving• Apparent movement– Displacement of objects• Induced movement• Movement aftereffect6Functions of Movement Perception• Survival in the environment– Predators use movement of prey as a primary means to location in hunting– Motion agnosia• Damage to the cortex resulting in inability to perceive movement• Extremely debilitating and dangerous for the patientFunctions of Movement Perception -continued• Perceiving objects– Movement of objects or the observer’s movement through objects help perceive the 3D organization of stimuli– Kinetic depth effect - movement of an object’s 2-D shadow can change into perception of a 3-D object• This is an example of structure-from-motion–Perceptual organizationFigure 9.4 Setup similar to the one used by Wallach and O’Connell (1953) to demonstrate the kinetic depth effect.– Demonstration: structure-from-motion• http://www.cs.ubc.ca/nest/imager/contributions/flinn/Illusions/Illusions.htmlVisual Pathway (MT)7The Physiology of Navigation• Optic flow neurons - neurons in the medial superior temporal area (MST) of monkeys respond to flow patternsDetermining Direction of Fields of Moving Dots• Firing and coherence experiment by Newsome et al.• Coherence of movement of dot patterns was varied• Monkeys were taught to judge direction of dot movement and measurements were taken from MT neurons• Results showed that as coherence of dot movement increased, so did the firing of the MT neurons and the judgment of movement accuracyPerceiving motionA monkey is shown random dots moving in a particular direction.• Neurons that are sensitive to a specific direction of motion.• Inhibitory connections8The intelligence of movement perception• Top-down processes– Certain stimuli (like the human body) have special meaning that affects perceptionFigure 9.18 Frames from the stimuli used by Grossman and Blake (2001). (a) Sequence from the point-light walker stimulus. (b) Sequence from the scrambled point-light stimulus.Biological Motion (Demonstration)http://www.biomotionlab.ca/Sensation & PerceptionCh. 10: Perception and Action© Takashi Yamauchi (Dept. of Psychology, Texas A&M University)Main topicsEcological approachOptic flowThe physiology of navigationSkilled actionLinking sensory and motor functionsPerception reconsidered• J. J. Gibson’s ecological approach– All the studies we have seen so far are conducted in laboratory settings, in which stationary stimuli were given. – Perception is not a stationary experience.– Perception should be studied as it occurs in the natural environment.Optic flow and a gradient of flow• A gradient of flow gives a strong cue for motion and depth perception9Demonstration:http://www.rdg.ac.uk/arl/clips/demo_of_displays.htm#opticflowNeural mechanism• Neurons that are sensitive to the direction of motion• sequential activation in a visual field induces the perception of movement.The Physiology of Navigation• Optic flow neurons - neurons in the medial superior temporal area (MST) of monkeys respond to flow patternsNeuron 1 in the monkey’s MST responds to an expanding stimulus but not a stimulus with circular movement. Neuron 2 responds to circular movement but not to expansion.Physiological Links Between Sensory and Motor Functions• Optic ataxia – Patients suffering from this syndrome produce inaccurate reaching movements towards a target or object in space.Experiment by Schindler et al.• Participants:2 groups• Patients with parietal lobe damage and normal controlparticipants.• Participants performed two tasks• Bisection task - point to position between cylinders• Reaching task - reach between cylinders and touch a gray stripBisection taskIn each trial, you saw two cylinders that were shifted different positions. You had to point a place exactly midway between the cylinders.10Experiment by Schindler et al.Bisection taskIn each trial, you saw two cylinders that were shifted different positions. You had to point to a place exactly midway between the cylinders.So, for each trial, you had to point different positions.Trial 1Trial 2pointpointExperiment by Schindler et al.Reaching taskIn each trial, you saw two cylinders that were shifted different positions. You had to touch a gray strip that were 20 cm behind the cylinders. So, for each trial, you had to extend your hand to different positions.Trial 1Trial 2touchtouchResults• Pointing task– The patients with parietal lobe damage and normal control were equally accurate• Reaching task– The patients kept reaching the