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Chapter 4

Summary of Chapter 4

Course Code
Michael Inzlicht

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Chapter 4 – Sensation and perception
-Sensation: stimulation of sense organs. (i.e. absorption of
energy, such as light or sound waves, by sensory organs)
-Perception: selection, organization, and interpretation of
sensory input. (i.e. translating sensory input something
- Psychophysics: the study of how physical stimuli are
translated into psychological experience.
Thresholds: looking for limits
-Threshold: dividing point between energy levels that do and
do not have a detectable effect.
-Absolute threshold: minimum amount of stimulation that an
organism can detect.
Weighing the differences: the JND
-Just noticeable difference (JND): the smallest difference in

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the amount of stimulation that a specific sense can detect.
-Webers Law: the size of a JND is a constant proportion of
the size of the initial stimulus.
-Weber fraction: constant proportion of the initial stimulus.
(approximately 1/30)
-As stimuli increase in magnitude, the JND becomes larger.
Psychological scaling
-Fechners law: the magnitude of a sensory experience is
proportional to the number of JNDs that the stimulus causing
the experience is above the absolute threshold.
-Constant increments in stimulus intensity produce smaller
and smaller increases in the perceived magnitude of
sensation. (ex. 3 equal increases in stimulus intensity (the
amount of light) produce progressively smaller differences in
the magnitude of sensation (perceived brightness))
Signal-Detection theory
-Signal-detection theory: detection of stimuli involves

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decision processes as well as sensory processes, which are
both influenced by a variety of factors besides stimulus
-Hits: detecting signals when they are present.
-Misses: failing to detect signals when they are present.
-False alarms: detecting signals when they are not present.
-Correct rejections: not detecting signals when they’re absent.
-According to this theory, your performance will also depend
on the level of noise in the system.
Perception without awareness
-Subliminal perception: registration of sensory input without
conscious experience.
-Perception without awareness can take place.
Sensory adaptation
-Sensory adaptation: gradual decline in sensitivity due to
prolonged stimulation.
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