sleep unit

Sensory receptors

Specialized cells that detect and respond to specific types of stimuli.

Transduction

The process by which sensory receptors convert stimuli into neural impulses.

Just Noticeable Difference (jnd)

The smallest difference in stimulation that can be detected 50% of the time; described by Weber’s Law.

Absolute Threshold

The minimum intensity of stimulus that must be detected for a person to sense it.

Signal Detection Theory

A theory that explains how and when we detect the presence of a faint stimulus amid background noise.

Habituation

A decrease in response to a stimulus after repeated presentations.

Adaptation

The process in which sensory receptors become less sensitive to constant stimuli.

Subliminal Stimuli

Stimuli that are below the threshold of conscious perception.

Top Down Processing

Information processing guided by higher-level mental processes, as we construct perceptions drawing on our experience and expectations.

Bottom Up Processing

Information processing that begins with sensory input, focusing on the analysis of smaller features to build up to a complete perception.

Properties of Light

Characteristics of light, including wavelength, intensity, and purity that influence our perception.

Cornea

The transparent front part of the eye that covers the iris and pupil.

Aqueous humor

The fluid found in the anterior chamber of the eye, providing nourishment and maintaining intraocular pressure.

Iris

The colored part of the eye that regulates the size of the pupil and controls the amount of light entering the eye.

Pupil

The adjustable opening in the center of the iris through which light enters the eye.

Lens

The transparent structure behind the pupil that changes shape to help focus images on the retina.

Retina

The light-sensitive layer at the back of the eye that converts light into neural signals.

Fovea

The central focal point in the retina, where visual acuity is highest.

Optic nerve

The nerve that carries neural impulses from the eye to the brain.

Vitreous humor

The clear gel that fills the space between the lens and the retina.

Rods

Photoreceptor cells in the retina that are sensitive to light and allow for vision in dim conditions.

Cones

Photoreceptor cells in the retina responsible for color vision and detail in bright light.

Ganglion cells

Neurons in the retina that receive input from bipolar cells and send visual information to the brain.

Bipolar cells

Cells that connect photoreceptors (rods and cones) to ganglion cells in the retina.

Visual accommodation

The process by which the lens of the eye changes shape to focus on nearby or distant objects.

Farsighted

A condition in which distant objects are seen clearly but nearby objects are blurry.

Nearsighted

A condition in which nearby objects are seen clearly but distant objects appear blurry.

Blindspot

The area on the retina where the optic nerve leaves the eye; no photoreceptor cells are present.

Dark adaptation

The process by which the eyes become more sensitive to low light levels.

Light adaptation

The process by which the eyes decrease sensitivity to light after exposure to bright light.

Trichromatic theory

The theory that color perception is based on three primary colors: red, green, and blue.

Opponent-process theory

The theory that color perception is controlled by the activity of three opponent systems: red-green, blue-yellow, and black-white.

After Image Effect

The phenomenon in which an image continues to appear in one's vision after the exposure to the original image has ceased.

Color blindness

A genetic condition where individuals are unable to perceive differences in certain colors; types include Monochrome, Red/Green, and Yellow/Blue.