AP Psychology Unit 2: Cognition

If you're studying for the AP Psychology exam, Unit 2 is where things get interesting. This unit covers how you perceive the world, think through problems, remember information, and measure intelligence. These concepts show up everywhere on the multiple choice section and in the free response questions, so understanding cognition is essential to your score.

In this review, we'll break down the eight topics in Unit 2, highlight what actually matters for test day, and show you where students typically make mistakes.

Topic 2.1: Perception

Sensation and perception are different, and the AP exam loves testing whether you know the difference. Sensation is when your sensory receptors pick up information from the environment. Perception is what your brain does with that information, organizing and interpreting it into something meaningful.

This topic focuses on how you perceive the world around you through visual, auditory, and other sensory systems. The key is understanding that perception isn't just about the information coming in—it's also shaped by your expectations, your past experiences, and what's going on around you.

Key concepts to know:

• Bottom-up and top-down processing: Bottom-up is when you build perceptions from raw sensory data working upward. Top-down is when your expectations and knowledge influence what you perceive. Both happen at the same time in real perception.
• Gestalt principles: These explain how your brain groups visual elements together. Closure means you fill in gaps to complete a figure. Figure-ground means you separate foreground from background. Proximity means elements close together seem related. Similarity means elements that look alike seem grouped. The exam tests these constantly.
• Depth cues: Your brain figures out how far away things are using binocular cues (like eye convergence and stereopsis) that require both eyes, and monocular cues (like linear perspective, relative size, texture gradient, interposition, and relative clarity) that work with just one eye.
• Perceptual constancies: You perceive objects as staying the same even when the sensory input changes. A white shirt looks white in daylight and shadow. Your phone looks the same size whether it's near or far. This is size constancy, shape constancy, and color constancy.
• Attention and selective attention: You can't process everything at once, so your brain focuses on what matters. The cocktail party effect is when you hear your name across a noisy room—your brain picks it out because it's important to you.
• Change blindness: Sometimes dramatic changes right in front of you go unnoticed if they happen during a moment you're not paying attention. This shows that perception requires attention.

Topic 2.2: Thinking, Problem-Solving, Judgments, and Decision-Making

This topic is about how you think through problems and make decisions. It covers the mental shortcuts you use, the cognitive biases that trip you up, and why you sometimes make irrational choices even when you have good information.

The core idea is that your brain uses different strategies depending on the situation. Sometimes you think carefully through every step. Sometimes you use mental shortcuts that usually work but can lead you astray.

Key concepts to know:

• Concepts and prototypes: A concept is a mental category, like "furniture" or "basketball player." A prototype is the best example of that category in your mind—so a couch is a prototypical piece of furniture, but a lamp is less prototypical. When you decide if something fits a category, you compare it to your prototype.
• Algorithms and heuristics: An algorithm is a step-by-step procedure that will always give you the right answer, like a math formula. A heuristic is a mental shortcut that usually works but isn't guaranteed. You use heuristics all the time because they save mental energy.
• Availability heuristic: You judge how common or likely something is based on how easily examples come to mind. If you just heard about a plane crash, you might overestimate how dangerous flying is because that example is vivid and easy to remember.
• Representativeness heuristic: You judge the probability of something based on how much it resembles a typical example. If someone is quiet and likes books, you might think they're more likely to be a librarian than an accountant, even if accountants outnumber librarians.
• Mental set and functional fixedness: A mental set is when you approach a problem the same way you've solved similar problems before, which can prevent you from seeing a fresh solution. Functional fixedness is when you can only think of an object's typical use, so you can't imagine using it in a new way.
• Priming and framing: Priming is when exposure to something activates related thoughts in your mind. Framing is when the way a choice is presented affects your decision. If a choice is framed as a loss, you're more likely to take risks to avoid it. If it's framed as a gain, you're more cautious.
• Common decision-making biases: The gambler's fallacy is thinking past results change the odds of future events (they don't). The sunk-cost fallacy is throwing good money after bad because you've already invested so much. Confirmation bias is seeking information that confirms what you already believe.
• Creativity and divergent vs. convergent thinking: Convergent thinking gets you to one correct answer by logical steps. Divergent thinking generates multiple possible answers by thinking flexibly. Creativity requires both—you need novel ideas (divergent) that actually solve the problem (convergent).

Topic 2.3: Introduction to Memory

Memory is one of the most heavily tested topics in Unit 2. The key is understanding the different types of memory and the models that explain how memory works.

There are different types of memories based on what you're remembering and how conscious you are of remembering it. Explicit memory (also called declarative) is when you consciously remember something—you know you're remembering. Implicit memory (also called nondeclarative) is when something influences your behavior without conscious awareness, like knowing how to ride a bike.

Key concepts to know:

• Types of explicit memory: Episodic memory is your memory for specific events, like what you had for lunch yesterday. Semantic memory is your memory for facts and general knowledge, like the capital of France.
• Types of implicit memory: Procedural memory is for skills and how to do things, like playing an instrument. Prospective memory is remembering to do something in the future, like remembering to study tomorrow.
• The multi-store model: This classic model says memory has three stages. Sensory memory holds information from your senses for a very short time (less than a second). Short-term or working memory holds a small amount of information for about 20-30 seconds. Long-term memory can hold unlimited information for years or life.

• Working memory model: A newer view of memory emphasizes that you actively manipulate information in working memory. It's not just a passive storage space—it's where thinking happens.
• Long-term potentiation: This is the physical basis of memory. When neurons fire together repeatedly, the connections between them strengthen. This is how memories get stored in your brain at the neural level.
• Levels of processing: The deeper you think about information, the better you remember it. Just reading words and noticing their appearance is shallow processing. Thinking about meaning is deep processing. Deep processing leads to better memory.

Topic 2.4: Encoding Memories

Encoding is getting information into memory in the first place. Different encoding strategies make huge differences in what you remember.

Key concepts to know:

• Mnemonic devices: These are techniques you use to encode information in a way that makes it easier to remember. The method of loci is when you mentally place items in specific locations (like rooms in a house) to remember them. First-letter mnemonics make a phrase out of first letters. Rhymes and patterns also work. The more creative and personal your mnemonic, the better it usually works.
• Chunking: You remember information better when you group it into meaningful chunks. Your phone number breaks into chunks. A date like 1492 chunks as a year. Chunking increases the amount of information you can hold in working memory.
• Spacing effect: Information spaced out over time is remembered better than information crammed all at once. This is huge for exam prep. Studying for 30 minutes daily for two weeks beats one 12-hour cram session before the exam.
• Serial position effect: You remember items at the beginning of a list (primacy effect) and the end of a list (recency effect) better than items in the middle. This happens because early items get more rehearsal and encoding, and recent items are still in working memory.

Topic 2.5: Storing Memories

Storing memories means keeping them in long-term memory over time. The strength of a memory depends on how you encoded it and how you maintain it.

Key concepts to know:

• Maintenance vs. elaborative rehearsal: Maintenance rehearsal is just repeating information to keep it in working memory (like saying a phone number over and over). Elaborative rehearsal is thinking about meaning and connecting new information to what you already know. Elaborative rehearsal creates stronger long-term memories.
• Storage duration and capacity: Your long-term memory seems to have unlimited capacity and can last a lifetime. This is a key difference from working memory, which is limited in both duration and capacity.
• Autobiographical memory: This is your memory for your own life experiences. It's shaped by emotion, importance, and how many times you've remembered it. Your most vivid autobiographical memories are often from important life events, like graduation or first dates.
• Amnesia types: Anterograde amnesia means you can't form new memories after brain injury. Retrograde amnesia means you can't remember events from before brain injury. Both show that memory involves physical changes in the brain.
• Alzheimer's disease: This neurodegenerative disease destroys neurons and causes severe memory loss, starting with episodic and semantic memories while procedural memory lasts longer.

Topic 2.6: Retrieving Memories

Retrieval is getting memories back out when you need them. Two main types of retrieval show up on the exam: recall and recognition.

Key concepts to know:

• Recall vs. recognition: Recall is retrieving information from memory with no cues, like on an essay test. Recognition is identifying information as familiar when you see it again, like on a multiple choice test. Recognition is usually easier because you have cues.
• Context-dependent memory: You remember information better when you're in the same context where you learned it. This is why cramming in your bedroom might not help you remember during the exam in the gym.
• Mood-congruent memory: When you're in a certain mood, you more easily remember information that matches that mood. If you're sad, sad memories come to mind more easily.
• State-dependent memory: You remember information better when you're in the same physical or mental state you were in when learning it. This is related to context but focuses on your internal state.
• Retrieval practice and the testing effect: Actually retrieving information (answering questions, taking practice tests) makes you remember it better than just studying. The more you retrieve, the stronger the memory becomes. This is one of the most important findings in learning science, and it applies directly to how you should study.

Topic 2.7: Forgetting and Other Memory Challenges

Forgetting isn't a failure of your memory system—it's often a normal and useful part of how memory works. But understanding why you forget helps explain what happens when memory goes wrong.

Key concepts to know:

• Encoding failure: You forget because you never encoded the information properly in the first place. You can't remember something you never really learned. This explains why you forget where you put your keys—you didn't encode the location.
• Forgetting curve: Herman Ebbinghaus showed that you forget information quickly at first, then the rate of forgetting slows. The first hours and days are critical. This is why spacing your studying matters so much.

• Proactive and retroactive interference: Proactive interference is when old learning interferes with new learning. You learned French in high school, and now Spanish is harder because you keep thinking of French words. Retroactive interference is when new learning interferes with old learning. Studying Italian might make you forget your French.
• Repression: Freud suggested that traumatic memories are pushed into the unconscious to avoid emotional pain. While repression is still debated, modern evidence suggests that truly repressed memories that suddenly resurface are extremely rare.
• Misinformation effect: False information after the event can alter your memory of what actually happened. If someone suggests something happened differently, you might remember it that way instead.
• Source amnesia: You remember information but forget where it came from. You might remember a fact but not know if you read it on social media or heard it from an expert.
• Constructive memory: Memory isn't like recording a video. You actively construct memories based on what actually happened plus your expectations, beliefs, and what you've heard since. This makes memory unreliable in ways you don't realize.

Topic 2.8: Intelligence and Achievement

Intelligence is one of the most controversial topics in psychology, partly because it's hard to define and measure. The exam tests how intelligence is measured, what IQ scores mean, and the factors that influence intelligence.

Key concepts to know:

• General intelligence (g): Psychologist Charles Spearman proposed that there's one underlying general intelligence factor that explains performance across different cognitive tasks. Though there's debate about whether this is the whole picture, g predicts real-world outcomes pretty well.
• IQ scores and standardization: IQ is calculated so the average is 100 and the standard deviation is 15. This means about 68% of people score between 85 and 115. The scores are standardized, meaning they're compared to a large reference group. Regular restandardization is necessary because scores have been rising over time (the Flynn Effect).
• Validity and reliability: A test is valid if it measures what it claims to measure. It's reliable if it gives consistent results. An IQ test can be reliable without being valid for every purpose, and vice versa.
• Flynn Effect: IQ scores have been rising over generations, probably because of better nutrition, more education, and increased test familiarity. This shows that IQ is influenced by environment, not just genes.
• Stereotype threat: When you're reminded of negative stereotypes about your group's abilities, your performance actually gets worse. This affects test performance and artificially lowers scores for people in stereotyped groups.
• Aptitude vs. achievement: Aptitude tests measure your potential to learn. Achievement tests measure what you've already learned. The distinction matters because a low achievement test score might reflect inadequate teaching rather than low ability.
• Fixed vs. growth mindset: If you believe intelligence is fixed (fixed mindset), you see challenges as threats and avoid them. If you believe intelligence grows through effort (growth mindset), you see challenges as opportunities to learn. Growth mindset leads to better learning and resilience.

Study Tips for Unit 2

This unit is heavy with vocabulary and concepts, but they're testable and important. Here's how to ace it:

Summary, Review Questions & Practice

You've covered all eight topics in Unit 2. Before you move on, test yourself with these scenario-based questions. If you can answer them confidently, you're in great shape for this section of the exam.

Explore the Full AP Psychology Study Guide

Unit 2 builds on the biological foundations from Unit 1. The memory topics connect to neural structures and brain function. You'll see cognition come up again in Unit 3 when you study how development affects thinking, and in Unit 5 when you learn about mental health and cognitive therapies.

Check out the full AP Psychology study plan to see how everything fits together.

Other Unit Reviews:

• Unit 1: Biological Bases of Behavior
• Unit 3: Development and Learning
• Unit 4: Social Psychology and Personality
• Unit 5: Mental and Physical Health

For official AP Psychology resources, visit apcentral.collegeboard.org.

This review is aligned with the AP Psychology Course and Exam Description. AP is a registered trademark of the College Board, which was not involved in the production of this guide.