Understanding Psychology (10th Ed)

adaptation
An adjustment in sensory 
capacity after prolonged exposure to 
unchanging stimuli.
Study Alert
Remember that Weber’s law 
holds for every type of sen-
sory stimuli: vision, sound, 
taste, and so on.
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R E C A P / E V A L U A T E / R E T H I N K
K E Y T E R M S
R E C A P
What is sensation, and how do psychologists study it?
• Sensation is the activation of the sense organs by any 
source of physical energy. In contrast, perception is the 
process by which we sort out, interpret, analyze, and in-
tegrate stimuli to which our senses are exposed. (p. 99) 
What is the relationship between a physical stimulus and the 
kinds of sensory responses that result from it?
• Psychophysics studies the relationship between the 
physical nature of stimuli and the sensory responses 
they evoke. (p. 99)
• The absolute threshold is the smallest amount of physi-
cal intensity at which a stimulus can be detected. Under 
ideal conditions absolute thresholds are extraordinarily 
sensitive, but the presence of noise (background stimuli 
that interfere with other stimuli) reduces detection capa-
bilities. (p. 100)
• The difference threshold, or just noticeable difference, is 
the smallest change in the level of stimulation required 
to sense that a change has occurred. According to 
Weber’s law, a just noticeable difference is a constant 
proportion of the intensity of an initial stimulus. (p. 101)
• Sensory adaptation occurs when we become accustomed 
to a constant stimulus and change our evaluation of it. 
Repeated exposure to a stimulus results in an apparent 
decline in sensitivity to it. (p. 102)