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Perceptual organization • How do we form meaningful perceptions from sensory information? Gestalt psychology • Branch of cognitive psychology • Organization of many sensations into perceptions of wholes – Gestalt = whole or form • Based on experience and expectations • Perceived whole is not always the same as its parts! Form perception • Simplification into easily interpretable wholes • Figure-ground Form perception • Grouping principles – Proximity – Similarity – Continuity – Connectedness – Closure Depth perception • Distance is perceived with vision and hearing • Visual depth perception – Binocular cues – Monocular cues Binocular depth cues • Retinal disparity – Strongest visual depth cue Monocular depth cues • Light and shadow • Relative size and position • Relative height/vertical position • Linear perspective Auditory location cues • Intensity and pitch • Arrival times at each ear • Clarity Perceptual constancy • Cognitive functions that maintain the features of an object, despite changing illumination, color, size, or shape – Based on comparisons between the figure and ground Color and lightness constancy • Consistent color and light intensity, despite changes in illumination Shape and size constancy • Familiar objects are perceived as unchanging despite changes in retinal images. Perceptual interpretation • Making sense of the perceptions produced by the cortex – Genetics – Experience • Critical periods • Plasticity and adaptation Perceptual set • Psychological predisposition to perceive stimuli in a particular way – Shaped by learned assumptions and beliefs – Affects how we interpret sensory stimuli • Examples Other sensory modalities Hearing • Stimulus - sound waves – Frequency – Amplitude The ear Auditory stimuli • Bending of hair cells in the cochlea transduces vibrations into neural signals • Auditory nerve • Primary auditory cortex • Auditory association cortex Touch • Stimulus - pressure, pain, warmth, cold – Receptors – Other sensations • Stimuli organized in primary somatosensory cortex • Perceptions created in somatosensory association cortex Pain • Critical alert system • Subjective – Physiology – Prior experiences – Attention – Context – Culture Pain • Gate-control theory • Pain control/management Taste • Stimulus - chemical molecules that impart the sensations of sweet, sour, salty, bitter and umami Sweet Sour Salty Bitter Umami • Tastebuds contain taste and touch receptors Taste perception • Flavor – Based on taste, olfactory, and touch stimuli • Begins in brainstem • Completed in the limbic system Taste preferences • Genetic predisposition • Biological predisposition • Learned responses Smell • Stimulus - chemical molecules • Receptors in olfactory epithelium – Axons project directly to the olfactory bulb of the brain – Perception begins in the olfactory bulb, completed in the limbic system Kinesthesis & vestibular sense • Kinesthesis - sense of body position and movement • Vestibular sense - sense of head postion and movement • Stimulus - gravity and movement • Receptors found in muscles (body) and inner ear (head) Kinesthesis & vestibular sense • Sensory signals about position and movement are organized in the medulla and cerebellum • Perception occurs throughout the brain – Brain stem – Temporal cortex
