Unit 2 covers the mental processes behind how we perceive the world, think through problems, remember experiences, and measure intelligence. It accounts for roughly 13–17% of the AP exam.
The unit opens with perception — how the brain constructs experience from sensory input using top-down and bottom-up processing, Gestalt principles, and prior knowledge. From there it moves to thinking and decision-making: the heuristics (availability, representativeness) and cognitive biases (confirmation bias, framing effect, functional fixedness) that shape and sometimes distort our judgment.
The largest section covers memory — the three-stage model (sensory, working, long-term), encoding through levels of processing and mnemonics, and the many ways we forget (interference, misinformation effect, source amnesia). The unit closes with intelligence: how it's defined, measured, and tested — including reliability, validity, standardization, and stereotype threat.
Key terms preview
A taste of what you’ll find in The Essentials and Flashcards.
Availability heuristic
Judging likelihood by how easily examples come to mind — overestimates dramatic or recent events.
Working memory
Briefly holds and actively manipulates information; limited capacity maintained by rehearsal.
Misinformation effect
Misleading post-event information can distort how we remember the original event (Loftus).
Levels of processing
Deeper, more meaningful encoding creates much stronger memories than shallow processing.
Stereotype threat
Concern about confirming a negative group stereotype can impair test performance.
Confirmation bias
Seeking and favoring information that confirms what we already believe.
Big Idea 1. Perception is constructed, not just received
Your brain combines bottom-up sensory data with top-down expectations to build what you 'see.' Gestalt principles, prior knowledge, and context all shape perception — meaning two people can witness the same event and perceive it differently.
Big Idea 2. We rely on mental shortcuts that usually work but sometimes fail
Heuristics like availability and representativeness help us decide quickly. These shortcuts are mostly useful but introduce predictable biases — confirmation bias, framing effects — that can lead to systematic errors in judgment.
Big Idea 3. Memory is a multi-stage process — and forgetting happens at every stage
Information moves from sensory memory to working memory to long-term memory through encoding. Each stage has different capacities and durations. Interference, decay, and retrieval failures explain why we forget.
Big Idea 4. How you encode determines what you remember
Deeper, meaningful (semantic) processing creates far stronger memories than shallow processing. Mnemonics, spacing practice, retrieval practice, and connecting new information to prior knowledge all dramatically improve recall.
Big Idea 5. Memory is reconstructive, not a recording
Each time you remember an event, you rebuild it from fragments. The misinformation effect (Loftus) and source amnesia show memories can be subtly altered by later information — a major reason eyewitness testimony is less reliable than intuition suggests.
Big Idea 6. Intelligence is real, measurable, and contested
Standardized tests aim for reliability and validity, but defining intelligence is debated — g-factor vs. multiple intelligences. Scores are influenced by culture, opportunity, and stereotype threat, not just innate ability.