Chapter 3: Sensation and Perception
● Sensation: Activation of receptors in various sense organs
● Sensory Receptors: Specialized forms of neurons that are stimulated by different kinds of energy
instead of neurotransmitter
● Subliminal Perception: Below conscious awareness
● Extrasensory Perception: Not through physical senses
○ Neither subliminal nor extrasensory perception have scientific validity
● Transduction: Turning outside stimuli into neural activity
○ Reaches special receptors in the sense organs
● Sensory Thresholds
○ Just noticeable difference (jnd or the difference threshold): Smallest difference between 2
stimuli that is detectable 50% of the time
○ Absolute threshold: Smallest amount of energy needed for a person to consciously detect a
stimulus 50% of the time
○ Subliminal stimuli: Stimuli that are below the level of conscious awareness
■ Just strong enough to activate the sensory receptors, but not strong enough for
conscious awareness
■ Subliminal perception
○ Signal detection theory: Provides a method for assessing the accuracy of judgments or
decisions under uncertain conditions; used in perception research and other areas.
● Habituation: The tendency of the brain to stop attending to constant, unchanging information
● Sensory adaptation: The tendency of sensory receptor cells to become less responsive to a stimulus
that is unchanging
● Microsaccades: Constant movement of the eyes; tiny vibrations people don’t notice consciously
○ Prevent sensory adaptation to visual stimuli
● Brightness is determined by the amplitude of the wave—how high or how low the wave actually is.
○ The higher the wave, the brighter the light will be
○ Low waves are dimmer
● Wavelengths
○ Saturation refers to the relative amount of whiteness in a color. As whiteness declines,
saturation increases
○ Humans normally see are a mixture of different wavelengths
■ Wave amplitude:
■ Wave form:
○ Light can vary in its purity depending on how varied the mixture of wavelengths are
The Parts of the Eye
● Cornea: Where light enters; Protects the eye
○ Photoreactive keratectomy (PRK) and laser-assisted keratomileusis (L A S I K) are vision
approving techniques that make small incisions in the cornea to change focus
● Aqueous Humor: The visual layer below cornea that supplies nourishment to the eye
● Pupil: Hole through which light from visual image enters interior of eye
● Lens: Right behind the cornea; Focuses light rays on the retina
○ Suspended by muscles and finishes the focusing process begun by the cornea
● Iris: The black center of eye that constricts or dilates depending on amount of light in the environment
and changes the size of pupil; Round muscle in which the pupil is located
● Retina:
○ Rods play a key role in night vision because they are more sensitive than cones to dim light.
○ Cones play a key role in daylight vision and color vision. Cones do not respond well to dim light,
but in bright light they provide more sharpness and detail than rods
● Sensation: Activation of receptors in various sense organs
● Sensory Receptors: Specialized forms of neurons that are stimulated by different kinds of energy
instead of neurotransmitter
● Subliminal Perception: Below conscious awareness
● Extrasensory Perception: Not through physical senses
○ Neither subliminal nor extrasensory perception have scientific validity
● Transduction: Turning outside stimuli into neural activity
○ Reaches special receptors in the sense organs
● Sensory Thresholds
○ Just noticeable difference (jnd or the difference threshold): Smallest difference between 2
stimuli that is detectable 50% of the time
○ Absolute threshold: Smallest amount of energy needed for a person to consciously detect a
stimulus 50% of the time
○ Subliminal stimuli: Stimuli that are below the level of conscious awareness
■ Just strong enough to activate the sensory receptors, but not strong enough for
conscious awareness
■ Subliminal perception
○ Signal detection theory: Provides a method for assessing the accuracy of judgments or
decisions under uncertain conditions; used in perception research and other areas.
● Habituation: The tendency of the brain to stop attending to constant, unchanging information
● Sensory adaptation: The tendency of sensory receptor cells to become less responsive to a stimulus
that is unchanging
● Microsaccades: Constant movement of the eyes; tiny vibrations people don’t notice consciously
○ Prevent sensory adaptation to visual stimuli
● Brightness is determined by the amplitude of the wave—how high or how low the wave actually is.
○ The higher the wave, the brighter the light will be
○ Low waves are dimmer
● Wavelengths
○ Saturation refers to the relative amount of whiteness in a color. As whiteness declines,
saturation increases
○ Humans normally see are a mixture of different wavelengths
■ Wave amplitude:
■ Wave form:
○ Light can vary in its purity depending on how varied the mixture of wavelengths are
The Parts of the Eye
● Cornea: Where light enters; Protects the eye
○ Photoreactive keratectomy (PRK) and laser-assisted keratomileusis (L A S I K) are vision
approving techniques that make small incisions in the cornea to change focus
● Aqueous Humor: The visual layer below cornea that supplies nourishment to the eye
● Pupil: Hole through which light from visual image enters interior of eye
● Lens: Right behind the cornea; Focuses light rays on the retina
○ Suspended by muscles and finishes the focusing process begun by the cornea
● Iris: The black center of eye that constricts or dilates depending on amount of light in the environment
and changes the size of pupil; Round muscle in which the pupil is located
● Retina:
○ Rods play a key role in night vision because they are more sensitive than cones to dim light.
○ Cones play a key role in daylight vision and color vision. Cones do not respond well to dim light,
but in bright light they provide more sharpness and detail than rods
