Chapter5Transparencies - CHAPTER 5 – SENSATION I –...

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CHAPTER 5 – SENSATION I – Definitions Sensation : The process by which sensory receptors and nervous system receive and represent stimulus energies from the environment. Perception : The process of organizing and interpreting sensory information, enabling recognition of meaningful objects and events. Bottom-up processing : Analysis that begins with the sense receptors and works up to the brain’s integration of sensory information. Top-down processing : Information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations. II – Basic Principles of Sensation Thresholds: Psychophysics: The study of relationships between the physical characteristics of stimuli, such as their intensity, and our psychological experience of them. Absolute threshold : The minimum stimulation needed to detect a particular stimulus 50 percent of the time. Signal detection theory : A theory predicting how and when we detect the presence of a faint stimulus (“signal”) amid background stimulation (“noise”). Assumes that there is no single absolute threshold and that detection depends partly on a person’s experience, expectations, motivation, and level of fatigue. Subliminal : Below one’s absolute threshold for conscious awareness. Can still be detected (see definition of absolute threshold – 50% detection) and can influence behavior – “PRIME” a response. Thus, we process information without being aware of it. BUT, subliminal perception is NOT the same as subliminal persuasion (powerful and enduring effects have NEVER been observed). Difference threshold : The minimum difference between two stimuli required for detection 50 percent of the time ( just noticeable difference or jnd ). Increases with the magnitude of the stimulus. Weber’s law : The principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount). Said another way, the difference threshold is not a constant amount but some constant proportion of the stimulus. 1
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Sensory Adaptation : Diminished sensitivity to a stimulus as a consequence of constant stimulation. Adaptive to focus on the NOVEL rather than the mundane. II – VISION Transduction : The conversion of one form of energy into another. In sensation, the transforming of stimulus energies into neural impulses. Stimulus input: Light energy Electromagnetic spectrum ranges from imperceptibly short waves of gamma rays, to the narrow band that we see as visible light, to the long waves of radio transmission. Other organisms are sensitive to differing portions of the spectrum. Wavelength : The distance from one wave peak to the next - determines Hue - the color we experience (e.g., blue). Intensity
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Chapter5Transparencies - CHAPTER 5 – SENSATION I –...

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