Lecture 8 _Interpretation and Illusions_

Lecture 8 _Interpretation and Illusions_ - 2/2/07 Psych 2...

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Unformatted text preview: 2/2/07 Psych 2 Principles of Psychology Christopher Gade Office: 5315 Tolman Hall Office hours: MW 2:00-3:00 Email: gadecj@berkeley.edu Lectures: MWF 3:00-4:00, 100 GPB Interpretation of Stimuli On Wednesday we learned about the physiological design of our visual system. Now we’re going to discuss the function of that system. Namely, we’re going to examine how we interpret the collection of visual stimuli that we are presented with. We’re also going to discuss how our system sometimes makes mistakes when it comes to visual stimuli, and explain why these mistakes are made. The Amazing World of Perception/Interpretation How do we know that an object is the same, despite the fact that it changes size and shape? • • Door example Chalk example Visual constancy: Our tendency to perceive objects as keeping their shape, size and color, even though what actually strikes our retina changes from time to time. A Few Amazing Things our Brain Does Color perception Object recognition Motion perception Depth perception The Interpretation of Colors and Patterns The Brightness Contrast • Method of determining the colors of objects (going beyond just the frequency of the electromagnetic waves). • The brightness of surrounding objects influences our perception of the color and brightness of an object. Feature Detection How exactly do we determine the features of an object? Studies have shown that our brain takes complex stimuli and breaks them down into component parts Where’s the proof??? Animal Research Neuroscientists have shown that specialized neurons in cats and monkeys respond to certain features that are presented to them (lines at different angles). Visual Illusion Example Repetitive exposure to an angle or motion can temporarily fatigue certain neurons. After the neurons are worn out, perceptual illusions can occur once the exhaustive stimuli is removed. • Spinning wheel example • Lines example Gestalt Psychology This feature detection concept is great. It allows us to understand how we perceive stimuli at a very basic level. But what about interpretation? How do we make sense of ambiguous stimuli? Gestalt psychology addresses this problem. Gestalt Psychology (cont.) Gestalt psychology is a field that focuses on our ability to perceive overall patterns. “The whole is different (and often greater) than the sum of its parts”. Our perception is based on our attempts to create semblance out of the mess of stimuli that we are presented with. Gestalt psychology claims that our perception operates on a total of seven different principles. Read the text to find out what these principles are and how they work. The Interpretation of Movement and Depth So…what do we know so far? 1. We know about how our eyes take in information from last lecture. 3. We now know how our mind process that visual information to give meaning to the information our eyes send to our brain. 5. We also know how our brain can make sense of ambiguous stimuli that we’re presented with. But what don’t we know? 1. How we can determine the motion of an object. 3. How we can determine the distance/depth of an object. Tricks to Determining Motion Distinguishing between self-motion and objectmotion. • Vestibular system Spinning example “Virtual Insanity” example • Induced movement (compare objects to background) Stroboscopic motion: illusion of motion created from rapid succession of stationary images. Flipbooks, movies, and Christmas lights. Tricks to Determining Distance/Depth Binocular Cues (two eyes) • Retinal disparity: the position of an object is determined by the different signals received by the two eyes. • Convergence: the distance of an object is determined by the amount of eye movement required to focus on an object. Monocular Cues (two eyes are not required) Object size (relative size): nearer objects look bigger. Accommodation: Our brains can detect how much the lens of the eye needed to shift in order to focus on an object. Detail (relative clarity): more detail signifies a closer object. Linear perspective: parallel lines converge. Relative height: the higher you are in view, the further away you are. Interposition: Determining proximity by what interrupts the view of other objects. Motion parallax: When moving, closer objects pass by faster than further objects. • Motion parallax video Visual Illusions So now we’ve learned about how our mind interprets visual stimuli in order to make sense of our world. Most of the time, this translation of information is very useful for our interaction with the real world. But sometimes, there are situations that trick the mind. Today, we’ll be discussing optical illusions. Optical Illusion: a misrepresentation of a visual stimulus. What are some common causes for these illusions? • Mixed visual signals being presented to the brain. • The mind’s attempt to transfer a 2 dimensional object into a 3 dimensional one. • Misuse of depth cues. Mixed Signals to the Brain The Muller-Lyer Illusion Two Dimensional Transformations Depth Perception Illusions The Ponso Illusion The Moon Illusion The Ames Room Watch the video… The End If you’re interested, you can learn about our other senses that we possess and how they work in the other chapter 4 sections. You are not required to know these, but they might be of interest to you. See you on Friday. ...
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This note was uploaded on 12/16/2008 for the course PSYCH 2 taught by Professor Don'tremember during the Spring '04 term at University of California, Berkeley.

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