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Sensation and Perception. Chapter 4. Defining Sensation and Perception. Sensation The detection of physical energy emitted or reflected by physical objects. It occurs when energy in the external environment or the body stimulates receptors in the sense organs. Perception
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Sensation and Perception Chapter 4
Defining Sensation and Perception • Sensation • The detection of physical energy emitted or reflected by physical objects. • It occurs when energy in the external environment or the body stimulates receptors in the sense organs. • Perception • The process by which the brain organizes and interprets sensory information.
Ambiguous Figure • Colored surface can be either the outside front surface or the inside back surface • Cannot simultaneously be both • Brain can interpret the ambiguous cues two different ways
The Riddle of Separate Sensations • Sense receptors • Specialized cells that convert physical energy in the environment or the body to electrical energy that can be transmitted as nerve impulses to the brain.
Sensory Overload • Overstimulation of the senses. • Let’s play an observation game! • Can use selective attention to reduce sensory overload. • Selective attention • The focusing of attention on selected aspects of the environment and the blocking out of others. • Inattentional blindness
Measuring Senses • Absolute threshold • Difference threshold • Signal-detection theory
Absolute Threshold • The smallest quantity of physical energy that can be reliably detected by an observer.
Absolute Sensory Thresholds • Vision: • A single candle flame from 30 miles on a dark, clear night • Hearing: • The tick of a watch from 20 feet in total quiet • Smell: • 1 drop of perfume in a 6-room apartment • Touch: • The wing of a bee on your cheek, dropped from 1 cm • Taste: • 1 tsp. Sugar in 2 gal. water
Pledge of Allegiance • I pledge allegiance
JND • Each slide of the Pledge of Allegiance increased the font size. • Did you notice?
Just Noticeable Difference (JND): The smallest amount of change in a stimulus that can be detected half the time. Stimulus Discrimination
Weber’s Law • JND is proportional to the magnitude of the stimulus • The larger the stimulus the larger the change must be to be noticed!!
For a difference to be perceptible, 2 stimuli must differ by a constant proportion, not amount Light: 8% Weight 2% Tone: .3% Weber’s Law:
Backmasking!! • Secret messages hidden in musical lyrics? • Let’s find out!! • Jeffmilner.com
Signal-Detection Theory • A psychophysical theory that divides the detection of a sensory signal into a sensory process and a decision process. (expectations, experience, anticipation)
Sensory Adaptation and Deprivation • Adaptation • The reduction or disappearance of sensory responsiveness when stimulation is unchanging or repetitious. • Prevents us from having to continuously respond to unimportant information. • Deprivation • The absence of normal levels of sensory stimulation.