Chapter Two: Perceptual Processes I: Visual and Auditory RecognitionChapter Introduction-PerceptionoUses previous knowledge to gather and interpret stimuli registered by the sensesoCombines aspects of both the outside world and your inner worldoCombines bottom up and top down processing Background on Visual Object Recognition-Object recognition or pattern recognitionoIdentify a complex arrangement of sensory stimuli and you perceive that this pattern is separate from its backgroundoWe recognize objects quickly and accurately The Visual System-Distal stimulusoThe actual object that is "out there" in the environment, the pen on your desk-Proximal stimulusoThe info registered on your sensory receptors, image that your pen creates on your retina-RetinaoCovers the inside back portion of your eye; contains millions of neurons that register and transmit visual info from the outside world -Object recognition depends primarily on shape, rather than on color or texture-Sensory memoryoLarge capacity storage system that records info from each of the senses with reasonable accuracyoIconic memory or visual sensory memory-Preserves an image of a visual stimulus for a brief period after the stimulus has disappeared -Primary visual cortexoLocated in the occipital lobe of the brain; the portion of your cerebral cortex that is concerned with basicprocessing of visual stimuli oThe first place where info from your two eyes is combined Organization in Visual Perception-One important principle of gestalt psychologyoHumans have basic tendencies to organize what they see; without any effort, we see patterns, rather than random arrangements oFigure: has distinct shape with clearly defined edgesoGround: the region that is "left over" forming the background-Ambiguous figure ground relationshipoFigure and the ground reverse from time to time, so that the figure becomes the ground and then becomes the figure againoVase faces effectoTwo components-The neurons in the visual cortex become adapted to one figure, such as the faces so you are more likely to see the alternative vase version-Furthermore, people try to solve the visual paradox by alternating between two reasonable solutions-Illusory contours (subjective contours)oWe see edges even though they are not physically present in the stimulusoIllusory white triangle in front of outline of a second triangle and three small blue circlesoThis triangle appears to be brighter than any other part of stimulusTheories of Visual Object Recognition-One early theoryoYour visual system compares a stimulus with a set of templates, or specific patterns that you have stored in your memoryoBut perception requires a more flexible system than matching a pattern against a specific template-Other two theories: feature analysis and recognition by componentsoMore sophisticated Feature Analysis Theory-Relatively flexible approach, in which a visual stimulus is composed of a small number of characteristics or components -Each visual characteristic is called a distinctive feature-The way we recognize letters of the alphabetoArgue that we store a list of distinctive features for each letter oLetter R: curved component, vertical line, and diagonal line-Can also explain how we perceive a wide variety of 2d patterns-Feature analysis theories are consistent with psychological research-Also compatible with evidence from neuroscience-ProblemsoShapes that occur in nature are much more complex than letters and numbers Recognition by Components Theory-Theory to explain how humans recognize 3d shapes-A specific view of an object can be represented as an arrangement of simple 3D shapes called geonsoGeons can be combined to form meaningful objects-An arrangement of three geons gives people enough info to classify an object-This theory is essentially a feature analysis theory that explains how we recognize 3D objects -View centered approachoProposes that we store a small number of views of 3d objects, rather than just one view Top Down Processing and Visual Object RecognitionDistinction Between Bottom Up and Top Down Processing-Bottom UpoEmphasizes that the stimulus characteristics are important when you recognize an objectoThe physical stimuli from the environment are registered on the sensory receptorsoThis info is then passed on to higher, more sophisticated levels in the perceptual systemoCombo of simple, bottom level features helps you recognize more complex, whole objects-Top DownoEmphasizes how a person's concepts, expectations, and memory can influence object recognitionoHigher level mental processes all help in identifying objectsoYou expect certain shapes to be found in certain locationsoPast experiencesoYour expectations at the higher level of visual processing will work their way down and guide our early processing of the visual stimulus oSpecific structures along the route between the retina and visual cortex may play a role-Object recognition requires both Top Down Processing and Reading-The Man ran example-Top down processing (TDP) can influence our ability to recognize a variety of objects-A theory of recognition must include factors other than the info in the stimulus -Word superiority effectoWe can identify a single letter more accurately and more rapidly when it appears in a meaningful word than when it appears alone by itself or else in a meaningless string of unrelated letters -The context of a sentence facilitates the recognition of a word in a sentence -Reuckl and odenoDemonstrated that both features of the stimulus and the nature of the context influence word recognitionoBoth bottom and top processes operate in a coordinated fashion-Previous letters in a word help you identify the remaining letters more quickly-The other words in a sentence also help you identify the individual words more quickly-Students reading sloppy handwritten not, more likely to rely on top down processing than when they were reading neatly printed text Overactive Top Down Processing and "Smart Mistakes" in Object Recognition-Overusing the strategy of TDP-Change blindnessoWe fail to detect a change in an objet or a scene-Inattentional blindnessoWhen we are paying attention to some events in a scene, we may fail to notice when an unexpected but completely visible object suddenly appears Change Blindness-Example: asking for directions; person asking completely changes but you don’t notice-When perceiving an entire scene, our TDP encourages us to assume that the basic meaning of the scene will