Chapter 3 psych - Sensation and Perception PDF

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Sensation and Perception...

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eChapter 3 : Sensation and Perception Basic Principles - Sensation - The process of receiving stimulus energies from the external environment - Perception - The process of organizing and interpreting sensory information Sensation and Perception - Bottom-up processing - Initiated by sensory input - Outside world’s influence on perception - Top-down processing - Initiated by cognitive processing - internal/mental world’s influence on perception - Expectations and prior understanding Sensation - Sensory receptors - Specialized cells that selectively detect and transmit sensory information to the brain - Cells send signals via distinct neural pathways - Photoreception (vision) - Detection of light - Mechanoreception (touch) - Detection of pressure, vibration, and movement - Chemoreception (smell and taste) - Detection of chemical stimuli Thresholds - Absolute threshold - The minimum amount of energy an organism can detect 50% of the time - Noise - Irrelevant and competing stimuli - Different thresholds - How much stimulus change is necessary for detection? - Just noticeable difference - JND increases with stimulus and magnitude - Weber’s law - To be perceived as different - Two stimuli must differ - By a constant minimum percentage - Not a constant amount Subliminal Perception - Influence of information below the level of conscious awareness - Vicary: EAT POPCORN - Strahan: thirsty v. non-thirsty words

Signal Detection Theory - Decision “Did I detect something?” - Information acquisition - Criterion (basis/motive for judgement) Factors Affecting Perception - Attention - Focusing awareness on a narrowed aspect of the environment - Selective attention - Cocktail party effect(automatic selection” - Shiftable - Novelty, size, color, movement, emotions - Inattentional blindness - Sustained attention - Executive attention - Cultural effects on attention and perception - Focal objects vs. context - Change blindness - Perceptual set - Predisposition or readiness to perceive something in a particular way - Sensory adaptation - Change in responsiveness of sensory system - Based on level of surrounding stimulation (darkened room, bright outdoors) Properties of Light - Wavelength - Distance between peaks - Perceived as hue - Some wavelengths beyond human sensation - Amplitude - Heat of wave - Perceived as brightness - Purity - Mixture of wavelengths - Perceived as saturation Structure of the Eye: Retina - Photoreceptor cells - Rods - Sensitive to even dim light, but no color - Function well in low illumination - Humans have approx. 120 million rods - Cones - Respond to color - Operate best under high illumination - Humans have approx. 6 million cones

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Fovea - Densely populated with cones vital to many visual tasks - Blind spot - Where the optic nerve leaves the eyeball Visual Processing - Feature detectors - Highly specialized cells in the visual cortex - Size, shape, color, movement, or combination - Deprivation studies: brain “learns” perception - Parallel processing - Binding Color Vision: Theories - Trichromatic theory - Three types of receptors - Green, blue, and red cones - Color blindness - One or more cone types is inoperative - Afterimage - Sensation remains after a stimulus is removed - Trichromatic theory cannot explain afterimages - Opponent process theory - Complementary color pairs Visual Perception - Organizing and interpreting visual signals - Dimensions - Shape - Depth - Motion - Constancy Shape - Gestalt psychology - Perceptions are naturally organized according to certain patterns - Whole is different from the sum of the parts - Gestalt principles - Figure-ground relationship - Closure - Proximity - Similarity Depth - The brain constructs perception of 3D from 2D images processed by the retina - Binocular cues - Disparity - Convergence

Motion - Humans have specialized motion detectors Constancy - Perceptual constancies - Recognition that objects do not physically change despite changes in vantage point and viewing conditions - Sensory information (retinal image) changes, but perceptual interpretation does not - Size, shape, and color constancies Properties of Sound - Wavelength: distance between peaks - Determines frequency - Perceived as pitch - Some wavelengths cannot be perceived - Amplitude - Height of wave - Perceived as loudness - Mixture of wavelengths: complex sounds - Perceived as timbre/ tone saturation Theories of Hearing - Place theory of pitch perception - Location of stimulation is important - Only explains perception of high frequencies - Frequency theory of pitch perception - Frequency of nerve firing - Limitations of neuronal firing rate - Volley principle - Cell clusters can exceed limitations of firing rate Auditory Processing - Pathways of auditory information - Cochlea...auditory nerve...brain stem...temporal lobe - Most information crosses to the other hemisphere - Localizing sound - Intensity - Distance - Sound shadow - Timing Other Senses: Preview - Skin senses - Touch, temperature, and pain - Chemical - Taste and smell - Kinesthetic

- Vestibular Skin(cutaneous) - Touch - Receptors...spinal cord...thalamus...somatosensory cortex of the parietal lobe - Temperature - Thermoreceptors: warm and cold - Simultaneous warm and cold perceived as hot - Pain - Mechanical, heat, chemical receptors - Fast and slow pain pathways - Endorphins - Perception of pain can vary Chemical - Taste - Receptors on tongue: papillae - Sweet, sour, bitter, salty.. Also unami etc. - Smell - Olfactory epithelium - Temporal lobe and limbic system - Kinesthetic - Movement, posture, orientation - Muscle fibers and joints - Proprioceptive feedback - Vestibular - Balance and acceleration - Semicircular canals...