AP Psychology Unit 1.6–1.9: Sensation, Vision, and Perception

Sensation

The process by which sensory receptors detect information from the environment, such as light, sound, and temperature, and send signals to the brain.

Perception

The process by which the brain organizes and interprets sensory information, allowing us to recognize and understand what we're experiencing.

Bottom-Up Processing

Processing that begins with sensory receptors detecting information and builds toward a complete perception.

Top-Down Processing

Processing in which the brain uses previous experiences, expectations, and existing knowledge to interpret sensory information.

Selective Attention

The ability to focus conscious awareness on one particular stimulus while filtering out other information competing for attention.

Cocktail Party Effect

The ability to focus on one conversation in a noisy environment while still noticing personally important information, such as someone saying your name.

Inattentional Blindness

Failing to notice a visible but unexpected object or event because your attention is focused on something else.

Change Blindness

Failing to notice changes in the environment, especially when the change occurs during a distraction or interruption.

Transduction

The process by which sensory receptors convert physical or chemical stimulation, such as light or sound vibrations, into electrical signals that the nervous system can process.

Absolute Threshold

The minimum intensity of a stimulus required for a person to detect it at least 50% of the time.

Subliminal Stimuli

Stimuli that are below the absolute threshold and therefore cannot be consciously detected reliably.

Signal Detection Theory

A theory explaining how people determine whether a faint stimulus is present.

Hit

Correctly detecting a stimulus that is present.

Miss

Failing to detect a stimulus that is present.

False Alarm

Reporting a stimulus when none is present.

Correct Rejection

Correctly identifying that no stimulus is present.

Difference Threshold (Just Noticeable Difference)

The smallest difference between two stimuli that a person can detect at least 50% of the time.

Weber's Law

The principle that detecting a difference between two stimuli generally requires a constant percentage change rather than a fixed amount.

Sensory Adaptation

A decrease in sensitivity to a constant, unchanging stimulus after prolonged exposure.

Wavelength

The distance between successive peaks of a light wave.

Amplitude

The height of a wave, which relates to its intensity.

Cornea

The transparent outer covering at the front of the eye that protects it and helps bend incoming light toward the retina.

Pupil

The adjustable opening in the center of the iris that allows light to enter the eye.

Iris

The colored muscular part of the eye that controls pupil size and regulates how much light enters.

Lens

A transparent, flexible structure that changes shape to focus incoming light onto the retina.

Retina

The light-sensitive tissue lining the back of the eye that contains rods and cones and begins processing visual information.

Rods

Photoreceptor cells that are highly sensitive to dim light and help with peripheral vision.

Cones

Photoreceptor cells responsible for color vision and fine visual details.

Fovea

A small central area of the retina with a high concentration of cones, responsible for the sharpest and most detailed vision.

Optic Nerve

The bundle of nerve fibers that carries visual information from the retina toward the brain.

Blind Spot

The location where the optic nerve exits the eye.

Bipolar Cells

Retinal neurons that receive signals from rods and cones and transmit information toward ganglion cells.

Ganglion Cells

Retinal neurons that receive processed visual information.

Visual Pathway

The sequence through which visual information travels: Rods/cones → Bipolar cells → Ganglion cells → Optic nerve → Thalamus → Visual cortex in the occipital lobe.

Feature Detectors

Specialized neurons in the visual cortex that respond to specific features of visual stimuli.

Parallel Processing

The brain's ability to process multiple aspects of visual information simultaneously.

Young-Helmholtz Trichromatic Theory

The theory that color vision begins with three types of cones sensitive to short, medium, and long wavelengths.

Opponent-Process Theory

The theory that color information is processed through opposing channels: red-green, blue-yellow, and black-white.

Afterimage

A visual sensation that continues after the original stimulus disappears, often appearing in an opposing color because of adaptation in visual processing.

Nearsightedness (Myopia)

A condition in which nearby objects appear clearer than distant objects because light from distant objects focuses in front of the retina.

Farsightedness (Hyperopia)

A condition in which nearby objects may appear blurry because the eye's focusing power is insufficient, causing light to focus behind the retina without accommodation.

Dichromatism

A form of color-vision deficiency in which a person has only two functioning cone color channels instead of the usual three.

Monochromatism

A condition in which a person has only one functioning color channel, resulting in little or no ability to distinguish different hues.

Olfaction

The sense of smell, which occurs when airborne chemicals activate receptors in the nose.

Gustation

The sense of taste, which occurs when chemicals in food activate taste receptor cells.

Sensory Interaction

The principle that different senses work together and influence one another to create our overall perception of the environment.

Tactile Sense

The sense of touch, involving receptors that detect physical stimulation such as pressure and vibration.

Nociceptors

Sensory receptors that respond to potentially damaging stimuli and send signals that contribute to the experience of pain.

Gate-Control Theory

The theory that pain signals can be increased or reduced by neural mechanisms in the spinal cord.

Kinesthesia

The sense that allows you to detect the movement of your body parts without needing to look at them.

Proprioception

Your awareness of the position and movement of your body parts, based on information from receptors in muscles, tendons, and other tissues.

Vestibular Sense

The sense responsible for detecting head movement, orientation, and balance.

McGurk Effect

A perceptual illusion in which conflicting visual and auditory speech information causes a person to hear a different sound from the one actually being played.

Perceptual Set

A mental predisposition to interpret sensory information in a particular way based on previous experiences, expectations, and assumptions.

Context Effects

The influence of surrounding information on how a stimulus is perceived.

Emotion and Motivation

Internal feelings and desires that influence what we pay attention to and how we interpret information.

Extrasensory Perception (ESP)

The claimed ability to receive information without using ordinary sensory processes.

Telepathy

The claimed ability to communicate thoughts directly between minds without using ordinary communication.

Clairvoyance

The claimed ability to perceive hidden or distant information without using normal senses.

Precognition

The claimed ability to know or predict future events through means other than ordinary reasoning or available evidence.

Confirmation Bias

The tendency to seek out, interpret, and remember information that supports existing beliefs while ignoring or undervaluing contradictory evidence.

Hindsight Bias

The tendency to believe that an event was predictable after already knowing its outcome, even if it was difficult to predict beforehand.

Gestalt Psychology

An approach to perception emphasizing that the brain organizes individual sensory elements into meaningful, unified patterns.

Figure-Ground Relationship

The brain's tendency to separate a visual scene into a figure, which is the main object of attention, and the ground, which is the surrounding background.

Proximity

The Gestalt principle that objects positioned close together tend to be perceived as belonging to the same group.

Similarity

The Gestalt principle that objects sharing characteristics such as color, shape, or size tend to be grouped together.

Closure

The tendency to mentally fill in missing information to perceive incomplete shapes or patterns as complete objects.

Continuity

The tendency to perceive lines and patterns as following smooth, continuous paths rather than as disconnected pieces.