Sensation and Perception: every key term you need (+ practice quiz)

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Sensation

The process of detecting physical energy from the environment through sensory receptors.

Perception

The process of organizing and interpreting sensory information to give it meaning.

Transduction

The conversion of physical stimulus energy (light, sound) into neural impulses the brain can read.

Absolute Threshold

The minimum stimulus intensity detectable 50% of the time.

Difference Threshold (JND)

The smallest detectable difference between two stimuli half the time; also called the just-noticeable difference.

Weber's Law

Two stimuli must differ by a constant proportion (not amount) to be perceived as different.

Signal Detection Theory

Predicts detection of faint stimuli depends on both intensity and the observer's expectations and motivation.

Sensory Adaptation

Reduced sensitivity to an unchanging stimulus over time, such as no longer noticing a smell.

Retina

Light-sensitive inner eye surface containing rods and cones where transduction of light begins.

Rods and Cones

Rods detect black, white, and gray in dim light; cones detect color and fine detail in bright light.

Optic Nerve & Blind Spot

The optic nerve carries visual information to the brain; where it exits creates a blind spot with no receptors.

Trichromatic Theory

The retina has three color receptors (red, green, blue) that combine to produce all color perception.

Opponent-Process Theory

Color vision relies on opposing pairs (red-green, blue-yellow, black-white); explains afterimages.

Cochlea

Coiled, fluid-filled tube in the inner ear where sound waves are transduced into neural impulses.

Place vs Frequency Theory

Place theory links pitch to the cochlear location stimulated; frequency theory links pitch to firing rate.

Bottom-Up Processing

Perception that starts with raw sensory input and builds toward the brain's interpretation.

Top-Down Processing

Perception guided by experience, expectations, and context to interpret sensory information.

Gestalt Principles

Rules by which the brain organizes elements into whole forms (figure-ground, proximity, similarity, closure).

Figure-Ground

Organizing the visual field into an object (figure) that stands out from its surroundings (ground).

Depth Perception

The ability to see in three dimensions and judge distance, present early per the visual cliff study.

Binocular Cues

Depth cues that require both eyes, such as retinal disparity and convergence.

Monocular Cues

Depth cues available to one eye, such as relative size, interposition, and linear perspective.

Perceptual Constancy

Perceiving objects as stable in shape, size, and color despite changes in the retinal image.

Perceptual Set

A mental predisposition to perceive one thing rather than another based on expectations.

Signal Detection Theory

Predicts when we detect faint stimuli amid noise; detection depends on experience, expectations, motivation, and fatigue, not a fixed threshold.

Weber's Law

To be noticed, two stimuli must differ by a constant proportion (not amount): about 2% for weight, 8% for light intensity.

Sensory Adaptation

Diminished sensitivity to an unchanging stimulus, letting us focus on informative changes; why you stop noticing a ticking clock.

Rods vs Cones

Rods: peripheral, dim-light, black-and-white; cones: fovea, color and detail, need bright light.

Feature Detectors

Hubel and Wiesel: visual cortex neurons respond to specific features such as edges, angles, and movement.

Parallel Processing

The brain simultaneously processes color, motion, form, and depth aspects of a scene, then integrates them.

Young-Helmholtz Trichromatic Theory

Retina has three cone types (red, green, blue); combinations produce all colors. Explains most color blindness.

Opponent-Process Theory

Retinal and thalamic cells process color in opposing pairs (red-green, blue-yellow, black-white); explains afterimages.

Place vs Frequency Theory

Place theory: pitch depends on where the cochlea's basilar membrane vibrates (high pitches); frequency theory: on the rate of neural firing (low pitches).

Conductive vs Sensorineural Deafness

Conductive: damage to eardrum/ossicles (mechanical); sensorineural: hair cell or auditory nerve damage — cochlear implants target this.

Gate-Control Theory

The spinal cord contains a neurological 'gate' that pain signals pass through; large-fiber activity (rubbing) or brain signals can close it.

Vestibular vs Kinesthetic Sense

Vestibular (semicircular canals) monitors head position and balance; kinesthesis (receptors in joints and muscles) tracks body-part position.

Gestalt Grouping Principles

Proximity, similarity, continuity, closure, and connectedness: rules by which we organize sensations into meaningful wholes.

Binocular Cues

Retinal disparity (greater difference between the two eyes' images = closer) and convergence (eye muscles turn inward for near objects).

Monocular Cues

Depth cues available to one eye: relative size, interposition, relative height, linear perspective, texture gradient, motion parallax.

Perceptual Constancy

Perceiving objects as unchanging in shape, size, color, and brightness even as retinal images change.

Perceptual Set

A mental predisposition, shaped by expectations and context, to perceive one thing and not another (top-down processing).

Sensory Interaction

One sense may influence another, as when smell shapes taste or the McGurk effect (seen lip movements alter heard speech).