Sleep, Sensation, & Perception

Consciousness

awareness of yourself and your environment.

Circadian rhythm (sleep/wake cycle)

the body’s internal 24-hour clock that regulates sleep, hunger, and body temperature.

Jet lag

a disruption of circadian rhythm caused by traveling across time zones.

Shift work

a schedule that requires people to work nights or rotating hours, often disrupting circadian rhythms and sleep quality.

NREM stage 1

the lightest stage of non-REM sleep where you drift in and out; brain waves slow down; experience hypnagogic sensations

Hypnagogic sensations

brief sensory experiences (like falling or floating) that occur as you enter sleep.

NREM stage 2

deeper non-REM sleep marked by sleep spindles (bursts of brain activity).

NREM stage 3

the deepest stage of non-REM sleep (slow-wave sleep) important for physical restoration and growth

REM sleep

a sleep stage with rapid eye movements, vivid dreaming, and brain activity similar to wakefulness.

REM rebound

increased REM sleep that occurs after REM deprivation.

Activation-synthesis theory (dreams)

result from the brain's attempt to make sense of random neural activity.

Consolidation theory (dreams)

help strengthen and stabilize memories.

Memory consolidation

the process where the brain stores and stabilizes memories during sleep.

Restoration of resources

the idea that sleep helps restore energy, repair tissues, and maintain brain function.

Insomnia

persistent difficulty falling or staying asleep.

Narcolepsy

a sleep disorder involving sudden, uncontrollable sleep attacks.

REM sleep behavior disorder

acting out dreams due to lack of normal muscle paralysis during REM.

Sleep apnea

repeated stops in breathing during sleep, causing poor sleep quality.

Somnambulism

sleepwalking during deep non-REM sleep.

Sensation

the process of detecting physical energy from the environment and sending it to the brain.

Transduction

converting sensory energy (light, sound, chemicals) into neural signals.

Absolute threshold

the smallest amount of stimulation needed to detect something 50% of the time.

Just-noticeable difference (JND)

the smallest change in a stimulus that can be detected.

Sensory adaptation

decreased sensitivity after constant exposure to a stimulus.

Weber’s law

to notice a difference, two stimuli must differ by a constant proportion

Synesthesia

a condition where stimulation of one sense triggers another (e.g., seeing sounds as colors).

Retina

the light-sensitive layer of cells at the back of the eye.

Blind spot

the point where the optic nerve leaves the eye, containing no photoreceptors.

Visual nerve (optic nerve)

the nerve that carries visual information from the retina to the brain.

Lens

the structure that focuses light onto the retina.

Accommodation

the lens changing shape to focus objects at different distances.

Nearsightedness

difficulty seeing far objects because the eye focuses light in front of the retina.

Farsightedness

difficulty seeing close objects because the eye focuses light behind the retina.

Photoreceptors

cells in the retina that detect light (rods and cones).

Rods

photoreceptors sensitive to low light; important for night vision.

Cones (blue, green, red)

photoreceptors responsible for color vision and detail.

Trichromatic theory

color vision comes from combining activity of three cone types (red, green, blue).

Opponent-process theory

color perception is controlled by opposing pairs (red-green, blue-yellow, black-white).

Afterimages

visual images that remain after a stimulus is removed, caused by opponent-process fatigue.

Ganglion cells

retinal cells that receive signals from photoreceptors and form the optic nerve.

Dichromatism

color blindness involving two functioning cone types.

Monochromatism

complete color blindness; only one type of cone or none work.

Prosopagnosia

inability to recognize faces (face-blindness).

Blindsight

the ability to respond to visual stimuli without conscious awareness, usually due to damage to the visual cortex.

Wavelength

determines color in vision and pitch in sound.

Pitch

the highness or lowness of a sound.

Amplitude

the height of a sound wave; determines loudness.

Loudness

perception of sound intensity.

Pitch perception

how the brain interprets pitch from sound waves.

Place theory

different frequencies vibrate different places on the basilar membrane.

Volley theory

neurons fire in alternating groups to create a higher combined firing rate for frequency perception.

Frequency theory

pitch is encoded by how fast auditory neurons fire.

Sound localization

determining where a sound comes from using timing and intensity differences.

Conduction deafness

hearing loss caused by damage to the outer or middle ear.

Sensorineural deafness

hearing loss caused by damage to the inner ear or auditory nerve.

Olfactory system

the sensory system for smell.

Thalamus

brain structure that relays sensory information (except smell).

Pheromones

chemical signals used in communication between members of the same species.

Gustation

the sense of taste.

Sweet, sour, salty, bitter, umami, oleogustus

the main basic tastes.

Taste receptors

sensory cells on the tongue that detect taste.

Supertasters

people with many taste buds, making them very sensitive to taste.

Medium tasters

people with an average number of taste buds.

Nontasters

people with fewer taste buds and lower taste sensitivity.

Sensory interaction

senses influencing each other (e.g., smell affects taste).

Warm/cold receptors

receptors in the skin that detect temperature changes.

Gate control theory

the spinal cord has a “gate” that can block or allow pain signals.

Phantom limb

feeling sensations (often pain) in a missing limb.

Vestibular sense

sense of balance and spatial orientation.

Semicircular canals

structures in the inner ear that help detect head movement and balance.

Kinesthesis

the sense of body position and movement.

Bottom-up processing

using sensory data to build a perception.

Top-down processing

using expectations, prior knowledge, or schemas to interpret sensory input.

Schema

a mental framework that organizes knowledge and influences perception.

Perceptual set

a readiness to perceive something in a certain way.

Gestalt psychology

the idea that the brain organizes sensory information into meaningful wholes.

Closure

perceiving incomplete figures as complete.

Figure and ground

the tendency to separate objects (figure) from their background (ground).

Proximity

grouping things that are close together.

Similarity

grouping similar items together.

Attention

focusing awareness on specific stimuli.

Selective attention

focusing on one stimulus while ignoring others.

Cocktail party effect

the ability to focus on one voice in a noisy room, especially when your name is mentioned.

Inattentional blindness

failing to notice something visible because attention is elsewhere.

Change blindness

failing to notice changes in the environment.

Binocular depth cues

depth cues that require both eyes.

Retinal disparity

slight difference between the images each eye sees, used to judge depth.

Convergence

inward turning of the eyes for close objects, used as a depth cue.

Monocular depth cues

depth cues available to one eye.

Relative clarity

hazier objects appear farther away.

Relative size

smaller objects appear farther away.

Texture gradient

textures become finer with distance.

Linear perspective

parallel lines appear to meet in the distance.

Interposition

closer objects block farther objects.

Apparent movement

perceiving movement when none exists (e.g., stroboscopic motion).