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Unformatted text preview: Chapter 7: Smell, Taste, Pain, Hearing, and Psychophysics Pg. 233-238 Sensation – the basic processes by which sensory organs and the nervous system respond to stimuli in the environment and to the elementary psychological experiences that result from those processes Perception – organizing of sensory information within the brain and the meaningful interpretations extracted from it Overview of Sensory Processes • Physical stimulus >> physiological response >> sensory experience • Raw sensory experience is not assessed but the individual’s ability to use that experience to guide a behavior • The Basic Anatomy of the Human Senses o Receptors – structures that respond to physical stimulus by producing electrical changes that can initiate neural impulses o Sensory neurons – carry neural impulses from the receptors to the central nervous system Sensory-specific pathways carry these impulses Sensory areas in the cerebral cortex analyze this neural input Every sensory experience is a product of brain activity • Transduction and Coding: Preserving Information about the Stimulus o Transduction – the process by which a receptor cell produces an electrical change in response to a physical stimulus Membrane of receptor cell becomes more permeable to certain particles when the appropriate type of stimulus energy acts on the cell Receptor potential – electrical change as a result of this particle movement o Energy variation of stimulus energy Quantitative variation – amount or intensity of energy Qualitative variation – kind of energy o Coding – preservation of stimulus energy information that is sent to brain • Sensory Adaptation: Responding to Change More Than to Steady States o In the absence of stimulation a sensory system becomes temporarily more sensitive; in the presence of stimulation it temporarily becomes less sensitive o Receptor cells mediate; if stimulus remains, rate of action potentials decrease Pg. 263-271 Psychophysics – study of the relationship between the physical characteristic of a stimulus and the sensory experience that it produces Detecting Weak Stimuli and Small Difference • The Absolute Threshold, and Why It is Not Absolute o Absolute threshold – faintest detectable stimulus of any given type o Determined by presenting the stimulus many times at various low intensities and each time asking the person if detect or not o Very arbitrary nature • Signal Detection as a Decision-Making Task o Response bias, the tendency to favor a particular response when unsure, may mask true aspect of absolute threshold o Hits, misses, false alarms, and correct rejection; by comparing proportion of hits to false alarms, can derive a measure of sensitivity independent of response bias called d’ • The Difference Threshold and Weber’s Law o Difference threshold ( just-noticeable difference jnd) – minimum difference that must exist between two stimuli to detect them as different in 50% of the trials...
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- Fall '08
- Physical stimulus, Sensory Experience