PSYC305 Perception S U.ppt

Perception Week 05 Lecture Outline  Bottom-up processing  Top-down processing Gestalt Approach Perception Is…  The process of organizing and interpreting (making sense of) information coming from our senses. Perception  It enables us to answer questions about the identity and location of object...

Perception Week 05 Lecture Outline  Bottom-up processing  Top-down processing Gestalt Approach Perception Is…  The process of organizing and interpreting (making sense of) information coming from our senses. Perception  It enables us to answer questions about the identity and location of objects. What is __________? Where is __________? 4 Perception Is…  The process of organizing and interpreting information from senses  Not an exact copy of “the world”  Based on our past experience and expectations Sensation and Perception  Perception occurs after our sense organs detect the stimulus and transform it into a neural signal. Sensation 6 Sensation and Perception  More specifically, perception occurs after our receptor cells in the sense organs detect the presence of a stimulus, transform the signal into an electrochemical signal and send it to the brain. 7 How do sensations become perceptions? 8 Perception Sensations become Perceptions through stages 1.Reception: 2.Transduction: 3.Transmission: 4.Organization: 5.Interpretation: How Sensations Become Perceptions  Each sensory organ (eye, ear, skin, tongue, nose) has a different kind of sensory receptor.  Each sensory organ receives stimulus energy from the environment and recodes it into a signal the brain can understand. PSY 325 Cognitive Psychology 10 For example: Sense Organ – EYE Receptor Cells: Rods and Cones 12 Perception Sensations become Perceptions through stages 1.Reception: 2.Transduction: 3.Transmission: 4.Organization: 5.Interpretation: Sensations become Perceptions through stages 1.Reception: receptor cells in the eyes sense/detect a stimulus. (That is, receptor cells detect the light reflected from the object) Sensations become Perceptions through stages 2. Transduction: Receptor cells in the sense organ (eyes) turns the signal from the environment into a neural signal (electrochemical signal). Transduction  The stimulus is converted or ‘transduced’ into neural/electrochemical signals.  A signal that the brain can understand. Sensations become Perceptions through… 3. Transmission: nerve cells send the neural signal to the visual cortex in the occipital lobe in the brain. Nerve cells = Optic Nerve Peaslee and Swartz, Virginia Government © 2014 CQ Press, an Imprint of SAGE Publications, Inc. Sensations become Perceptions through… 4. Organization: neurons in different regions of the visual cortex detect different characteristics of the stimulus. v1 -edge v4-color Peaslee and Swartz, Virginia Government © 2014 CQ Press, an Imprint of SAGE Publications, Inc. Organisation  We start forming a mental representation of the stimulus. Sensations become Perceptions through… 5.Interpretation: questions regarding meaning and location can be answered. This happens when the neural signal reaches the temporal and parietal lobe through ventral and dorsal stream. Peaslee and Swartz, Virginia Government © 2014 CQ Press, an Imprint of SAGE Publications, Inc. Ventral Stream Ventral Stream (Occipital to Temporal pathway): What? Information about the identify of stimuli. Dorsal Stream Dorsal Stream (Occipital to Parietal pathway): Where? Information about the location of stimuli. What type of operations do you think the mind executes to identify/recognize a stimulus? Interpretation  It compares incoming information with what is already known.  Interpretation involves the brain using knowledge in order to make sense of what it is considering. Class Activity I am going to show you four pictures with circles on. Your task is to write down what is included in the circle. PSY 325 Cognitive Psychology 27 Class Activity I am going to show you four pictures with circles on. Your task is to write down what is included in the circle. PSY 325 Cognitive Psychology 28 Class Activity What are the objects under the circle? PSY 325 Cognitive Psychology 29 PSY 325 Cognitive Psychology 30 PSY 325 Cognitive Psychology 31 PSY 325 Cognitive Psychology 32 PSY 325 Cognitive Psychology 33 Caption: “Multiple personalities of a blob.” What we expect to see in different contexts influences our interpretation of the identity of the “blob” inside the circles. (Source: Andrew Hollingsworth. 2005. Memory for object position in natural scenes. Visual Cognition, 12, 1003–1016. Reprinted by permission of the publisher, Taylor & Francis Ltd, http://www.tandf.co.uk/journals. Photographs courtesy of Antonio Torralba.) PSY 325 Cognitive Psychology 34 What are the objects under the circle? They are all the same. Your answer was governed by topdown processing. PSY 325 Cognitive Psychology 35 What are the objects under the circle? They are all the same. Your answer was governed by topdown processing. PSY 325 Cognitive Psychology 36 Top-down Processes  Top-down processing involves making inferences based on context, experience, and prior knowledge. Top-down Processes  Top-down processing  Perception may start with the brain  Person’s knowledge, experience, expectations Top-down processing The idea that pre-existing representations influence current perception. What you know affects what you see. Our expectations guide what we perceive. Bottom-up Processes  Bottom-up processing Perception comes from stimuli in the environment Parts are identified and put together, and then recognition occurs Bottom-up Processes  Bottom-up processing  Perception may start with the senses  Incoming raw data  Energy registering on receptors Bottom-up Processing Perception is conducted starting with the most basic units or features of a stimulus and adding the parts together to understand and identify a coherent whole object. PSY 325 Cognitive Psychology 43 PSY 325 Cognitive Psychology 44 Question Does perception start from our expectations or from our senses? Which of the two processes play a major role in perception? Approaches to Understand Perception  Direct perception theories (Gibson, 1966)  Bottom-up processing  Constructive perception theories (Gregory, 1970)  Top-down processing Approaches to Understand Perception  Direct perception theories (Gibson, 1966)  Bottom-up processing  Constructive perception theories (Gregory, 1970)  Top-down processing Both processes contribute to Perception! Approaches to Understand Perception  Direct perception theories  Bottom-up processing Perception comes from stimuli in the environment Parts are identified and put together, and then recognition occurs  Constructive perception theories  Top-down processing People actively construct perceptions using information based on expectations Caption: “Multiple personalities of a blob.” What we expect to see in different contexts influences our interpretation of the identity of the “blob” inside the circles. (Source: Andrew Hollingsworth. 2005. Memory for object position in natural scenes. Visual Cognition, 12, 1003–1016. Reprinted by permission of the publisher, Taylor & Francis Ltd, http://www.tandf.co.uk/journals. Photographs courtesy of Antonio Torralba.) Top-down theory: Helmholtz’s Theory Of Unconscious Inference (~1860)  Some of our perceptions are the result of unconscious assumptions we make about the environment  We use our knowledge to inform our perceptions  We infer much of what we know about the world  Likelihood principle: we perceive the world in the way that is “most likely” based on our past experiences Why is that the case? we perceive the world in the way that is “most likely” based on our past experiences Thank you! Gestalt Theory  A theory of perceptual organization.  It explains how we come to perceive stimuli in the world as we do.  By describing five principles of perceptual organization. Principles of Perceptual Organization 1. 2. 3. 4. 5. Proximity Similarity Closure Good continuation Good figure Principles of Perceptual Organization When you look at a stimulus. Our perceptual system looks for regularities.  Our perceptual system organizes and groups items in the simplest way.  By applying these five rules/principles. For example: What do you see below? Gestalt Psychology  A theory of perceptual organization Mind is holistic  Perceives objects as whole objects  We notice “features” later Gestalt Approach Theory proposes that the whole object is perceived before its parts. Gestalt Approach Theory proposes that the whole is greater than the sum of its parts. Gestalt Approach – Five Principles It proposes that the mind groups patterns (stimuli) in the world according to principles of perceptual organization. 1.Proximity 2.Similarity 3.Closure 4.Good continuation 5.Good figure Principle of Similarity When items in the world vary in similarity, our minds perceive similar items as part of the same group or form. Principle of Similarity When items in the world vary in similarity, our minds perceive similar items as part of the same group or form. Describe the picture below: Describe the picture below: Why do you perceive as columns and not rows? Describe the picture below: Why do you perceive as columns and not rows? Your mind groups similar items together. Principle of Proximity When elements in the world vary in proximity, we perceive elements that are close together as part of the same group. Principle of Proximity When elements in the world vary in proximity, we perceive elements that are close together as part of the same group. Describe the picture below: Principle of closure When objects in the world are missing a part or parts are occluded, our mind fills in the gap and perceive it as whole. Principle of closure When objects in the world are missing a part or parts are occluded, our mind fills in the gap and perceive it as whole. Describe the picture below: Principle of Good Continuation  When elements overlap, our minds connect elements in a way that makes them seem continuous or flowing in a particular direction. Principle of Good Continuation  When elements overlap, our minds connect elements in a way that makes them seem continuous or flowing in a particular direction. Describe the picture below: Describe the picture below: Describe the picture below: Principle of Good Continuation Principle of Good Figure  When elements overlap, we tend to perceive them in the most simple way. 80 Principle of Good Figure  When elements overlap, we tend to perceive them in the most simple way. 81 Describe the picture below: 82 A B C Principle of Good Figure The principle says that our perception of a stimulus, as in (A), will be organized into as cohesive a figure as possible: symmetrical, simple, closed, and regular. We see the figure that was shown in (A) as two regular figures in (B) and not the actual lines in (C). Gestalt Exercise  Each group needs to identify the principle that are involved in how we perceive the object below: Figure-ground We perceive scenes by segregating them as figure and background. What you see depends on what you assign as a background. Figure-ground When we are presented with a scene, our minds automatically separate figure and background. Test your knowledge! What do you see below? Which process account for what you see? WHY? 90 Class Exercise Complete Navon’s task using the link below: https://www.psytoolkit.org/experiment-li brary/navon.html What does the task measure? What were your results? PSY 325 Cognitive Psychology 91 Thank you!