Psychology Chapter on Sensation and Perception

Sensation

• Sensation is the process of activating receptors in the sense organs.
• Sensory receptors are specialized neurons that make up the nervous system.
• Sense organs include the eyes, ears, nose, skin, and taste buds.

Sensory Thresholds

• The just noticeable difference (jnd) or difference threshold is the smallest difference between two stimuli that can be detected 50% of the time.
• The absolute threshold is the smallest amount of energy needed for a person to consciously detect a stimulus 50% of the time it is present.

Subliminal Sensation

• Subliminal stimuli are stimuli that are below the level of conscious awareness.
• They are strong enough to activate sensory receptors but not strong enough for conscious awareness.
• Subliminal perception is the process by which subliminal stimuli act upon the unconscious mind, influencing behavior.

Habituation and Sensory Adaptation

• Habituation is the tendency of the brain to stop attending to constant, unchanging information.
• Sensory adaptation is the tendency of sensory receptor cells to become less responsive to a stimulus that is unchanging.
• Microsaccades are constant, tiny eye movements that prevent sensory adaptation to visual stimuli.

Psychological Aspects of Light

• Brightness is determined by the amplitude of the light wave.
• Color or hue is determined by wavelength.
• Saturation is the purity of the color.

Structure of the Eye

• The cornea is the clear outer layer of the eye that protects the eye and helps focus light.
• The pupil is the opening in the center of the iris that allows light into the eye.
• The iris is the colored part of the eye that controls the size of the pupil.
• The lens focuses light onto the retina.
• The retina is the light-sensitive lining of the back of the eye that contains photoreceptor cells called rods and cones.
• Rods are responsible for vision in low light conditions.
• Cones are responsible for color vision.
• The optic nerve carries visual information from the retina to the brain.

Visual Perception

• The trichromatic theory of color vision states that there are three types of cones, each sensitive to a different wavelength of light: red, green, and blue.
• The opponent-process theory of color vision states that color vision is based on three pairs of opposing processes: red-green, blue-yellow, and black-white.

Structure of the Ear

• The outer ear consists of the pinna, ear canal, and eardrum.
• The middle ear contains three small bones: the hammer, anvil, and stirrup.
• The inner ear contains the cochlea, a snail-shaped structure filled with fluid.
• The organ of Corti, located inside the cochlea, contains receptor cells for hearing.
• The auditory nerve carries auditory information from the cochlea to the brain.

Hearing and Sound

• The frequency of a sound wave determines its pitch.
• The amplitude of a sound wave determines its loudness.

Taste and Smell

• Taste buds, located on the tongue, are responsible for taste.
• The olfactory epithelium, located in the nasal cavity, is responsible for smell.
• Taste and smell are closely linked.

Touch, Pain, Motion, and Balance

• The skin contains receptors for touch, pressure, temperature, and pain.
• The vestibular sense is responsible for our sense of balance and spatial orientation.
• The kinesthetic sense is responsible for our awareness of our body's position and movement.

Perception

• Perception is the process of organizing and interpreting sensory information.
• Perceptual constancy is the tendency to perceive objects as unchanging even though the sensory information we receive from them changes.
• Gestalt principles of perception are a set of rules that help us organize our perceptions.
• Depth perception is the ability to perceive the world in three dimensions.
• Visual illusions are perceptions that do not match reality.

Gestalt Principles of Perception

• Figure-ground: The tendency to perceive objects as separate from their backgrounds.
• Proximity: The tendency to perceive objects that are close together as belonging to the same group.
• Similarity: The tendency to perceive objects that are similar to each other as belonging to the same group.
• Closure: The tendency to complete figures that are incomplete.
• Continuity: The tendency to perceive patterns that are continuous rather than discontinuous.

Depth Perception

• Monocular cues are depth cues that can be perceived with one eye.
• Binocular cues are depth cues that require the use of both eyes.
• Linear perspective: The tendency for parallel lines to appear to converge in the distance.
• Texture gradient: The tendency for textures to appear finer and smoother in the distance.
• Aerial perspective: The tendency for objects in the distance to appear hazier than objects in the foreground.
• Relative size: The tendency for larger objects to appear closer than smaller objects.

Visual Illusions

• Illusions occur when the brain interprets sensory information incorrectly.
• Illusions can provide insights into how the brain processes information.