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Chapter 3: Sensation and Perception Sensation: activity of receptor organs Perception: interpretation of sensory system activity Visual system organization: Each eye projects to both left and right hemisphere. Same half of each retina monitors opposite visual field
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Eye
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Retina and photoreceptors
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Rods: 125 mil; low light; color blind; peripherally located Cones: 7mil; daylight; color vision; centrally located
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Gathering visual information When scanning a visual scene (such as the picture on the left) or reading text (right), they engages in jerky, jumping movements called saccades. Ave fixation = approx. 250/ms; Ave saccade = 25-175/ms; visual suppression during saccade Change blindness: failure to detect visual changes during saccade Inattention blindness: failure to detect signal due to inattention, despite visual fixation Focal attention: processing object features during fixation (object interpretation) Trans-saccadic memory: coordinating objects across fixations to build up overall scene
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Span of Apprehension: How much info gathered in brief glance at visual pattern? Iconic memory Early studies: 4.5 unconnected letters; whole report technique; ‘reading off visual icon’ 1960 Partial report technique of George Sperling
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Pattern Recognition: Perceiving meaningful objects Gestalt Organizing Principles: Stimulus information combined with innate organizing principles of sensory systems. Need examples of principles (proximity, similarity, common fate, closure, and overriding principle of Pragnanz
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Stored canonical view: Evidence for Template approach
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Template matching But what about K K K K K K
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Selfridge (1959) Pandemonium model: Example of Feature Analysis Approach Parallel Processing of critical features and feature combinations
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Physiological evidence for FA Hubel and Wiesel find feature detectors in occipital lobe of cat
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Connectionist (PDP) word recognition model Feature analysis model based more closely on brain function. Both top- down (incorporating context effects) and bottom up (critical features) influences. Three layers, input (features), hidden (feature combo), and output (meaningful pattern) Highly interconnected with varied + and – weighted connections between nodes
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Recognition by Components Meaningful forms base on combinations of primitive “geons”. Geon: simple 3D geometric forms Intersections are most informative of geon Evidence: recoverable vs. non-recoverable forms Weakness: very bottom-up; expertise effects (experts don’t show same non- recoverable effects as novices) and context effects (non-recoverable can be overcome by context)
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Visual Agnosia: failure of object recognition Prosopagnosia: inability to recognize familiar faces associated with damage to fusiform gyrus of temporal lobe Apperceptive agnosia: inability to coalesce features into meaning whole (object or form). RH/parietal lobe malfunction Associative agnosia: unable to associate form with meaning or identity. Ex: can define form (hammer is to pound) but cannot identify hammer form. Temporal visual stream damage and corpus collosum
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Audition: the ear Mechanical function based on incoming vibrations. Higher frequencies processed nearer the base of cochlea, lower nearer the apex.
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Auditory Sensory Memory “Three eared man” studies. Whole report = little over 4 items, partial = early 5, partial advantage maintained with 4 sec delay. Because of longer lasting echo memory, modality effect: better memory for end of list items if presented auditorily compared to visually.
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Conceptually driven auditory perception: phonemic restoration effect
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