1.5-2.1 sleep, sensation, perception

circadian rhythm

The body’s 24-hour biological clock that regulates sleep, wakefulness, body temperature, and hormone levels.

two main types of sleep

NREM (Non-Rapid Eye Movement) and REM (Rapid Eye Movement) sleep.

NREM stage 1

Light sleep, alpha → theta brain waves; easy to wake; may experience hypnic jerks.

NREM stage 2

Deeper sleep; sleep spindles and K-complexes appear on EEG; body temp and heart rate slow.

NREM stage 3 and 4

Deepest sleep (slow-wave sleep); delta brain waves dominate; hard to wake; body repairs tissue and releases growth hormone.

REM sleep

Vivid dreaming, rapid eye movement, increased brain activity, and temporary muscle paralysis.

REM rebound

When a person goes into REM sleep faster and stays in it longer after being deprived of REM sleep.

Main functions of sleep

Restoration (repair body and brain) and consolidation (strengthen memories and learning).

Insomnia

Difficulty falling or staying asleep.

Sleep apnea

Temporary stoppage of breathing during sleep that causes repeated awakenings.

Narcolepsy

A disorder where a person suddenly falls into REM sleep during the day.

Sleepwalking

Walking or performing activities during NREM Stage 3 or 4 sleep.

Night terrors

Intense fear or screaming during deep NREM sleep, often without memory of the event.

Sensation

The process of sensing our environment through touch, taste, sight, sound, and smell.

Transduction

When sensory organs convert stimuli into neural signals for the brain.

Threshold (Absolute Threshold)

The smallest amount of stimulus a person can detect.

Just Noticeable Difference

The smallest change in a stimulus that can be noticed.

Sensory Adaptation

When your senses stop noticing something after being exposed for a while.

Weber’s Law

The bigger the stimulus, the bigger the change needed to notice a difference.

Sensory Interaction

When one sense affects another, like smell influencing taste.

Vision

The ability to see using light that enters the eyes.

Retina

The light-sensitive layer at the back of the eye that detects images.

Lens

The clear structure that focuses light onto the retina.

rods

Cells in the retina that help you see in dim light.

cones

Cells in the retina that detect color and work best in bright light.

color vision

The ability to see different colors through cone cells in the eyes.

Trichromatic Color Theory

The idea that we see color using three types of cones: red, green, and blue.

Opponent-Process Color Theory

The theory that color vision is controlled by pairs like red-green and blue-yellow.

Blind Spot

The area in the eye where no vision occurs because there are no receptor cells.

Sound waves

Vibrations that travel through the air and let us hear sound.

Wavelengths (pitch)

The distance between waves that determines pitch in sound.

Amplitude (loudness)

The height of sound waves that determines how loud something is.

Frequency Theory (pitch perception)

The idea that pitch is determined by how fast the sound waves make neurons fire.

Place Theory (pitch perception)

The idea that pitch depends on which part of the cochlea is activated.

Sensorineural Deafness

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

Chemical Senses

The senses of taste and smell that detect chemicals in the environment.

Gustation

the sense of taste

Olfactory System/Bulb

The part of the brain that processes smells.

Perception

The way our brain organizes and interprets sensory information.

Top down processing

When we use past knowledge or expectations to understand what we sense.

Bottom up processing

When we use details from the environment to build up what we perceive.

Schemas

Mental frameworks that help us organize and interpret information.

Perceptual sets

A readiness to see something in a certain way based on expectations.

Gestalt psychology

The idea that we see things as whole patterns, not just parts.

Closure

Filling in missing pieces of an image to see a complete picture.

Figure/ground

Seeing objects (figure) as separate from their background (ground).

Selective attention

Focusing on one thing while ignoring others.

Change blindness

Not noticing big changes in a visual scene.

Inattention

Missing something visible because your attention is on something else.

Binocular depth cues

Depth cues that use both eyes to see distance.

Retinal disparity

The slight difference between what each eye sees that helps us judge distance.

Convergence

When your eyes move inward to focus on something close.

Monocular depth cues

Depth cues that only need one eye to see distance.

Linear perspective

When parallel lines seem to meet in the distance.

Interpositiong

When one object blocks another, making it look closer.

Perceptual consistency

Seeing objects as the same even when lighting, size, or angle changes.