AP Psych: Sensory Thresholds & Adaptation, Perceptual Organization & Interpretation, Vision: Photoreceptors & Processing, Depth & Visual Perception and Sensory Integration & Cognition

Absolute threshold

The minimum stimulation needed to detect a stimulus 50% of the time. Example: The quietest sound you can hear about half the time.

Signal detection theory

The idea that detecting a stimulus depends on both the stimulus itself and your alertness, expectations, and motivation. Example: Hearing your name in a noisy room.

Difference threshold

The minimum difference between two stimuli that a person can detect 50% of the time. Also called the just noticeable difference (JND). Example: Noticing that one backpack is slightly heavier than another.

Weber's law

The principle that the difference needed to notice a change depends on the original intensity of the stimulus. Example: Adding one pound to a 5-pound object is easier to notice than adding one pound to a 50-pound object.

Sensory adaptation

When sensory receptors become less sensitive to constant, unchanging stimulation. Example: No longer noticing the smell of perfume after wearing it for a while.

Gustav Fechner

Psychologist who helped establish psychophysics by studying the relationship between physical stimuli and psychological experiences.

Ernst Weber

Psychologist known for Weber's law, which explains how much a stimulus must change for us to notice a difference.

Perceptual set

A mental expectation that influences how you interpret sensory information. Example: Expecting to see a certain word makes you more likely to read a blurry word that way.

Gestalt

The idea that we naturally organize information into meaningful patterns and see the whole rather than just individual parts. Example: Seeing a complete picture instead of separate shapes.

Figure-ground

Organizing what you see into a main object (figure) and its background (ground). Example: Reading black words (figure) on a white page (ground).

Grouping

The brain's tendency to organize separate pieces of information into groups or patterns. Example: Seeing nearby dots as belonging together.

Perceptual constancy

Recognizing that an object stays the same even when its appearance changes. Example: A door still looks like the same door when it opens.

Color constancy

Perceiving an object's color as relatively unchanged even under different lighting conditions. Example: A white shirt still looks white in sunlight or shade.

Perceptual adaptation

The ability to adjust to changes in sensory information or the environment. Example: Adjusting to wearing glasses that slightly distort your vision.

Phi phenomenon

An illusion of movement created when separate stationary lights flash on and off quickly. Example: Marquee lights that appear to move around a theater sign.

Young-Helmholtz trichromatic (three-color) theory

The theory that color vision comes from three types of cones sensitive to red, green, and blue wavelengths. Example: Combining signals from these cones allows us to see many different colors.

Opponent-process theory

The theory that color vision works through opposing color pairs: red-green, blue-yellow, and black-white. Example: Seeing a green afterimage after staring at red.

Feature detectors

Specialized brain cells that respond to specific visual features, such as lines, edges, angles, and movement.

Parallel processing

The brain's ability to process multiple aspects of information at the same time. Example: Recognizing an object's color, shape, and movement simultaneously.

Depth perception

The ability to see objects in three dimensions and judge their distance. Example: Knowing how far away a car is.

Visual cliff

An experiment used to study depth perception in infants by creating the appearance of a drop-off over a safe surface.

Binocular cue

A depth cue that requires both eyes to work together.

Retinal disparity

The slight difference between the images seen by your left and right eyes. The brain uses this difference to judge depth.

Monocular cue

A depth cue that can be used with just one eye. Example: Objects that appear smaller often seem farther away.

Sensory interaction

The way different senses work together and influence one another. Example: Smell and taste working together to help you enjoy food.

Embodied cognition

The idea that our physical sensations and body movements can influence our thoughts, judgments, and decisions. Example: Holding a warm drink may make someone perceive another person as friendlier.