cueprepAP Psychology Unit 3: Sensation and Perception — Complete Review
Unit 3 examines how we detect physical energy from the environment (sensation) and how we organize and interpret that information (perception). You'll learn the difference between absolute thresholds, difference thresholds (Weber's law), and signal detection theory — concepts that explain why we notice some stimuli and miss others.
Vision and hearing receive the most attention. For vision, you'll trace the path from light hitting the cornea through the lens to the retina's rods and cones, then through the optic nerve to the visual cortex. For hearing, you'll follow sound waves from the outer ear through the cochlea's hair cells to the auditory cortex. You'll also study the chemical senses (taste and smell), touch, pain (gate-control theory), and the vestibular and kinesthetic senses.
The perception half of the unit covers how the brain organizes raw sensory data into meaningful experiences. Key topics include Gestalt principles (proximity, similarity, closure, continuity), depth perception (binocular and monocular cues), perceptual constancies, and top-down vs. bottom-up processing.
Key Concepts
Transduction
The conversion of physical energy (light, sound waves, pressure) into neural signals that the brain can process.
Absolute Threshold
The minimum stimulation needed to detect a stimulus 50% of the time — the faintest sound you can hear, dimmest light you can see.
Signal Detection Theory
The theory that stimulus detection depends not just on signal strength but also on the perceiver's experience, expectations, motivation, and alertness.
Weber's Law
The principle that the just noticeable difference (JND) between two stimuli is a constant proportion of the original stimulus, not a fixed amount.
Gestalt Principles
Rules the brain uses to organize sensory information: proximity, similarity, closure, continuity, and figure-ground.
Depth Perception
The ability to perceive distance, using binocular cues (retinal disparity, convergence) and monocular cues (relative size, interposition, linear perspective).
Top-Down vs. Bottom-Up Processing
Top-down processing uses prior knowledge and expectations to interpret stimuli; bottom-up processing builds perception from raw sensory data.
Gate-Control Theory
The theory that the spinal cord contains a 'gate' mechanism that can block or allow pain signals from reaching the brain.
Key Terms & Vocabulary
41 terms you need to know for Unit 3. Use our flashcards to memorize them with spaced repetition.
Study Unit 3 with Flashcards
Master Sensation and Perception using spaced repetition — the science-backed method that puts concepts in long-term memory with less study time.
Frequently Asked Questions
What is AP Psychology Unit 3 about?
Unit 3 covers sensation and perception — how our sensory organs detect stimuli from the environment (sensation) and how our brain organizes and interprets that information into meaningful experiences (perception). Key topics include vision, hearing, touch, the chemical senses, Gestalt principles, and depth perception.
How much of the AP Psychology exam is Unit 3?
Unit 3: Sensation and Perception accounts for approximately 6–8% of the AP Psychology exam.
What is the difference between sensation and perception?
Sensation is the process of detecting physical energy from the environment through sensory receptors (eyes, ears, skin, etc.). Perception is the brain's process of organizing and interpreting that sensory information to give it meaning. Sensation is bottom-up; perception often involves top-down processing.
What are the Gestalt principles of perception?
The Gestalt principles describe how we organize visual information: proximity (grouping nearby objects), similarity (grouping similar objects), closure (completing incomplete figures), continuity (seeing smooth patterns), and figure-ground (distinguishing objects from backgrounds).