PSYC 2000 Chapter : Chapter 3 Psych
The ABCs of Sensation
3.1 How does sensation travel through the central nervous system, and why are some
sensations ignored?
• Sensation is the activation of receptors located in the eyes, ears, skin, nasal cavities, and
tongue.
• Sensory receptors are specialized forms of neurons that are activated by different
stimuli such as light and sound.
• A just noticeable difference is the point at which a stimulus is detectable half the time it
is present.
• Weber’s law of just noticeable differences states that the just noticeable difference
between two stimuli is always a constant.
• Absolute thresholds are the smallest amount of energy needed for conscious detection of
a stimulus at least half the time it is present.
• Subliminal stimuli are stimuli presented just below the level of conscious awareness and
subliminal perception has been demonstrated in the laboratory. It has not been shown to
be effective in advertising.
• Habituation occurs when the brain ignores a constant stimulus.
• Sensory adaptation occurs when the sensory receptors stop responding to a constant
stimulus.
The Science of Seeing
3.2 What is light, and how does it travel through the various parts of the eye?
• Brightness corresponds to the amplitude of light waves, whereas color corresponds to the
length of the light waves.
• Saturation is the psychological interpretation of wavelengths that are all the same (highly
saturated) or varying (less saturated).
• Light enters the eye and is focused through the cornea, passes through the aqueous
humor, and then through the hole in the iris muscle called the pupil.
• The lens also focuses the light on the retina, where it passes through ganglion and bipolar
cells to stimulate the rods and cones.
3.3 How do the eyes see, and how do the eyes see different colors?
• Rods detect changes in brightness but do not see color and function best in low levels of
light. They do not respond to different colors and are found everywhere in the retina
except the center, or fovea.
• Cones are sensitive to colors and work best in bright light. They are responsible for the
sharpness of visual information and are found in the fovea.
• Trichromatic theory of color perception assumes three types of cones: red, green, and
blue. All colors would be perceived as combinations of these three.
• Opponent-process theory of color perception assumes four primary colors of red, green,
blue, and yellow. Colors are arranged in pairs, and when one member of a pair is activated,
the other is not.
• Color blindness is a total lack of color perception whereas color-deficient vision refers to
color perception that is limited primarily to yellows and blues or reds and greens only.
The Hearing Sense: Can You Hear Me Now?
3.4 What is sound, and how does it travel through the various parts of the ear?
• Sound has three aspects: pitch (frequency), loudness, and timbre (purity).
• Sound enters the ear through the visible outer structure, or pinna, and travels to the
Document Summary
It has not been shown to be effective in advertising: habituation occurs when the brain ignores a constant stimulus, sensory adaptation occurs when the sensory receptors stop responding to a constant stimulus. 3. 3 how do the eyes see, and how do the eyes see different colors: rods detect changes in brightness but do not see color and function best in low levels of light. They do not respond to different colors and are found everywhere in the retina except the center, or fovea: cones are sensitive to colors and work best in bright light. They are responsible for the sharpness of visual information and are found in the fovea: trichromatic theory of color perception assumes three types of cones: red, green, and blue. All colors would be perceived as combinations of these three: opponent-process theory of color perception assumes four primary colors of red, green, blue, and yellow.
