PerceptionOutline1. From Sensation to Representation?Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 192. Theoretical Approaches to PerceptionSlide 21Slide 22Slide 233. Deficits in PerceptionPerceptionChapter 4Outline1. From Sensation to Representation1. Basic Concepts2. Perceptual Constancies3. Depth Perception4. Gestalt Approaches to Form Perception2. Theoretical Approaches to Perception1. Bottom-Up Approaches2. Top-Down Approaches3. Deficits in Perception1. From Sensation to Representation1. Basic Concepts•Perception–The set of processes by which we recognize, organize, and make sense of the sensations we receive from environmental stimuli•Percept–Complex mental representation integrating particular sensational aspects of a figure?Pick an example of a complex percept and identify the individual sensational aspects the percept consists of.1. From Sensation to Representation1. Basic Concepts•Perceptual experience involves four elements:–Distal (far) stimulus•The object in the external world–Informational medium•Reflected light, sound waves, chemical molecules, or tactile information coming from the environment–Proximal (near) stimulus•Representation of the distal stimulus in sensory receptors (e.g. picture on the retina)–Perceptual object•Mental representation of the distal stimulus?Can you provide an example of perceptual processing of a particular object?Identify distal object, informational medium, proximal stimulus and perceptual object.1. From Sensation to Representation2. Perceptual Constancies•Perceptual constancy–Occurs when our perception of an object remains the same even when our proximal sensation of the distal object changes–Two cases of perceptual constancies:•Size constancy•Shape constancy1. From Sensation to Representation2. Perceptual Constancies•Size constancy–The perception that an object maintains the same size despite changes in the size of the proximal stimulation•The same object at two different distances projects different-sized images on the retina•Size constancy can be used to elicit illusions (e.g. Ponzo illusion or Müller-Lyer Illusion)1. From Sensation to Representation2. Perceptual Constancies•Shape constancy–The perception that an object maintains the same shape despite changes in the size of the proximal stimulus•Involves the perceived distance of different parts of the object from the observer1. From Sensation to Representation3. Depth Perception•Importance of depth perception–When you drive, you use depth to assess the distance of an approaching automobile–When you decide to call out to a friend walking down the street, you determine how loudly to call, based on how far away you perceive your friend to be1. From Sensation to Representation3. Depth Perception•Monocular depth cues–Represented in just two dimensions and observed with just one eye1. Texture gradient - Larger grains, farther apart2. Relative size - the closer the bigger3. Interposition- closer object partially obscures other object; farther object is partially obscured by other object1. From Sensation to Representation3. Depth Perception•Monocular depth cues (cont.)4. Linear perspective - apparently parallel lines seem to converge as they approach the horizon 5. Aerial perspective - the closer the object the crisper images seem, more clearly delineated6. Motion paralax- objects approaching get larger and move quickly closer1. From Sensation to Representation3. Depth Perception•Binocular depth cues1. Binocular convergence-The closer the object you are trying to see, the more your eyes must turn inward-Your muscles send messages to your brain regarding the degree to which your eyes are turning inward, and these messages are interpreted as cues indicating depth1. From Sensation to Representation3. Depth Perception•Binocular depth cues2. Binocular Convergence-The closer an object is to you , the greater the disparity between the views of it as sensed in each of your eyes-The apparent jumping of images between the two eyes, which indicates the amount of binocular disparity, will decrease with distance1. From Sensation to Representation4. Gestalt Approaches to Form Perception•Structuralism vs. Gestalt Psychology–Structuralist approach to from perception is decompositional and thus focused on breaking wholes into elementary components–The goal of Gestalt psychology was to address directly the more global, holistic processes involved in perceiving structure in the environment1. From Sensation to Representation4. Gestalt Approaches to Form Perception•Gestalt principles–Figure-ground•When perceiving a visual field, some objects (figures) seem prominent, and other aspects of field recede into the background (ground)–Proximity•We tend to perceive objects that are close to each other as forming a group–Similarity•We tend to perceive objects that are similar to each other as forming a group1. From Sensation to Representation4. Gestalt Approaches to Form Perception•Gestalt principles (cont.)–Continuity•We tend to perceive smoothly flowing or continuous forms rather than disrupted of discontinuous ones–Closure•we tend to perceptually close up, or complete, objects that are not, in fact, complete?Which Gestalt principles are applied in this display?+ O + O + O + O+ O + O + O + O+ O + O + O + O+ O + O + O + O+ O + O + O + O?Which Gestalt principles are applied in this display?2. Theoretical Approaches to Perception1. Bottom-Up Approaches- Start from the bottom, considering physical stimuli being perceived and then work their way up to higher-order cognitive processes (organizing principles and concepts)- Higher cognitive processes can not directly influence processing at lower levels2. Theoretical Approaches to Perception1. Bottom-Up Approaches•Gibson’s Theory of direct perception–The array of information in our sensory receptors, including sensory context, is all we need to perceive anything–We do not need higher cognitive processes or anything else to mediate between our sensory experiences and our perceptions–Existing beliefs or higher-level inferential thought processes are not necessary for perception2. Theoretical Approaches to Perception2. Top-Down Approaches•The perceiver builds (constructs) a cognitive understanding (perception) of a stimulus, using sensory information as the foundation for the structure but