How Do We Organize Knowledge?

Concepts, categories, and the knowledge we bring to an inference.

Level: Intermediate
Reading load: 8 core readings in 5 units
Prerequisites: No prior course in concepts or cognitive neuroscience is required. The path introduces its central terms, but several readings contain formal models or substantial theoretical discussion. How Can We Study the Mind? provides useful preparation in comparing models with evidence. How Do We Remember—and Why Do We Forget? offers background on memory, but neither is a prerequisite.
Last reviewed: September 2026

Introduction

Knowledge lets a new thing enter a familiar world. We recognize a chair, choose what to pack, or form an expectation about an animal we have never seen. Yet an object can belong to several useful groupings, and a typical example may teach us less than an unusual one. How do concepts make these judgments possible, and what would distinguish competing accounts?

Begin by separating levels of categorization from differences among members. Then compare a summary of a category with remembered examples, examine how background knowledge changes an inference, and ask what goals and cultural experience contribute. Finally, connect accounts of how knowledge and meanings are organized with evidence about how we represent that knowledge and select what is relevant to a task.

The eight core works include conceptual arguments, experiments, a book chapter, and research syntheses. Treat their disagreements as opportunities to compare predictions: what information does an account assume, what process uses it, and what finding would make us revise it?

Unit 1 of 5

What makes something a good example?

A category can be broad or narrow, and its members can differ in typicality. Start by keeping those observations separate from claims about the mechanism that produces them. A familiar example makes the distinctions concrete without settling the theory.

Reading
1 of 8
Principles of Categorization
Rosch, E. (1978). Principles of categorization. In E. Rosch & B. B. Lloyd (Eds.), Cognition and categorization (pp. 27–48). Lawrence Erlbaum Associates.
Foundational argument · Major synthesis · Moderate · Full work: 22 pages
Use this chapter to distinguish levels of categorization, family resemblance, and typicality. Carry that descriptive framework into the later comparisons without assuming that a typicality effect proves a stored average.
A question to consider. Choose an everyday object and give it broad, basic, and narrower labels. How would you investigate its typicality separately from the question of whether it belongs to each category?

Unit 2 of 5

Do we classify by summaries or remembered examples?

Different representations can produce similar-looking judgments. The task is to find a comparison on which they diverge. This formal paper develops an instance-based account and uses training and transfer patterns to challenge specific alternatives.

Reading
2 of 8
Context Theory of Classification Learning
Medin, D. L., & Schaffer, M. M. (1978). Context theory of classification learning. Psychological Review, 85(3), 207–238. https://doi.org/10.1037/0033-295X.85.3.207
Foundational argument · Landmark empirical study · Challenging · Full work: 32 pages
Turn Rosch's distinction between a phenomenon and its explanation into a model comparison. Follow the verbal meaning of the equations and the transfer predictions; a typical-looking response can arise without consulting an abstract prototype.
A question to consider. Which training or transfer comparison would distinguish the context model from the independent-cue accounts tested, even if both predict a general advantage for typical items?

Unit 3 of 5

How does knowledge support an inference?

Similarity becomes an explanation only when we specify what makes two things similar for the task. Medin examines this problem conceptually; Heit and Rubinstein then vary the property people are asked to generalize. Use the experiment to sharpen the argument rather than expecting it to settle every theory of concepts.

Reading
3 of 8
Concepts and Conceptual Structure
Medin, D. L. (1989). Concepts and conceptual structure. American Psychologist, 44(12), 1469–1481. https://doi.org/10.1037/0003-066X.44.12.1469
Major synthesis · Critical reappraisal · Moderate · Full work: 13 pages
Ask what prototypes and exemplars leave open about why particular features matter. Examine the premises of the knowledge-based argument and its obligation to make constrained predictions.
A question to consider. Why might changing what you believe about an object's mechanism alter its category without changing its appearance, and what would a similarity account need to specify to explain that change?
Reading
4 of 8
Similarity and Property Effects in Inductive Reasoning
Heit, E., & Rubinstein, J. (1994). Similarity and property effects in inductive reasoning. Journal of Experimental Psychology: Learning, Memory, and Cognition, 20(2), 411–422. https://doi.org/10.1037/0278-7393.20.2.411
Landmark empirical study · Methodological contribution · Moderate · Full work: 12 pages
Apply the preceding argument to a crossed experimental comparison. Distinguish an animal pair's overall resemblance from the features relevant to the property being inferred.
A question to consider. What pattern of judgments would rule out one fixed similarity ranking across anatomical and behavioral questions, and what alternative mechanisms would still remain possible?

Unit 4 of 5

How do goals and experience change categories?

Useful groupings depend partly on what people are trying to accomplish and the knowledge their activities make available. Compare categories assembled for a goal with patterns observed across expertise and cultural settings. Ask which claims generalize beyond the task and population studied.

Reading
5 of 8
Ad Hoc Categories
Barsalou, L. W. (1983). Ad hoc categories. Memory & Cognition, 11(3), 211–227. https://doi.org/10.3758/BF03196968
Landmark empirical study · Foundational argument · Moderate · Full work: 17 pages
Return to typicality with categories whose members may share a purpose rather than a familiar label. Compare graded judgments with evidence that category links are already established in memory.
A question to consider. For a category such as things to take on a rainy walk, what would distinguish a shared typicality ordering from fast, familiar access to its members?
Reading
6 of 8
The Native Mind: Biological Categorization and Reasoning in Development and Across Cultures
Medin, D. L., & Atran, S. (2004). The native mind: Biological categorization and reasoning in development and across cultures. Psychological Review, 111(4), 960–983. https://doi.org/10.1037/0033-295X.111.4.960
Major synthesis · Critical reappraisal · Methodological contribution · Challenging · Full work: 24 pages
Reconsider the earlier accounts using people whose everyday activities support different biological knowledge. Examine the comparisons that help explain variation without treating cultural labels as causes.
A question to consider. If experts and novices differ in generalizing a disease, which comparison could distinguish ecological knowledge from a failure to understand the task, and how might it change your interpretation of the earlier induction experiments?

Unit 5 of 5

How is meaning organized and used?

An account of knowledge needs both a representation and a process that uses it. First examine a historical network model with explicit timing predictions. Then consider a neural and computational framework that separates representing concepts from selecting the information relevant now.

Reading
7 of 8
Retrieval Time from Semantic Memory
Collins, A. M., & Quillian, M. R. (1969). Retrieval time from semantic memory. Journal of Verbal Learning and Verbal Behavior, 8(2), 240–247. https://doi.org/10.1016/S0022-5371(69)80069-1
Landmark empirical study · Historical turning point · Moderate · Full work: 8 pages
Make the proposed network answer to response-time evidence. Relate its hierarchical organization to Rosch's category levels while keeping a descriptive taxonomy separate from a retrieval mechanism.
A question to consider. What assumptions must hold before a longer verification time counts as evidence for traversing more links, and how could expertise complicate that inference?
Reading
8 of 8
The Neural and Computational Bases of Semantic Cognition
Lambon Ralph, M. A., Jefferies, E., Patterson, K., & Rogers, T. T. (2017). The neural and computational bases of semantic cognition. Nature Reviews Neuroscience, 18(1), 42–55. https://doi.org/10.1038/nrn.2016.150
Major synthesis · Foundational argument · Challenging · Full work: 14 pages
Bring representation and task-dependent use together. Compare the framework's evidence about integration and control with the earlier behavioral accounts of similarity, knowledge, and goals.
A question to consider. If someone knows an object's usual function but struggles to use it for a new goal, what evidence would distinguish a limitation in represented knowledge from difficulty controlling its use?

Scope and omissions

The path concentrates on object and biological concepts, category-based inference, and semantic cognition. It distinguishes a category's structure from its mental representation, and representation from the processes used in a particular judgment. Formal and neural models are introduced through the claims they help evaluate.

It is not a comprehensive account of all human knowledge. Abstract and social concepts, conceptual combination, relational concepts, scripts and schemas, and discourse receive limited treatment. Development and cultural experience enter through selected comparisons, not complete surveys. Optional works extend exemplar models, developmental inference, semantic networks, and later theories of induction. Clinical classification and the measurement of individual differences have different purposes from the categorization tasks examined here.

Synthesis

Knowledge gives new experience an order, but the order we use depends partly on the judgment we need to make. Category summaries, remembered examples, and knowledge of mechanisms offer different resources for recognition and inference. Goals and cultural experience can change their use. The central distinction is between the organization visible in judgments, the representation proposed to explain it, and the processes that bring it to bear.

Imagine organizing unfamiliar tools for two purposes: identifying what each one is and choosing something to solve a new practical problem. Explain how a prototype, remembered examples, and knowledge of mechanisms could support different judgments. Specify one observation on which two of those accounts would disagree.

Then change the person's goal or experience. Explain which grouping or inference might change and why that need not mean the person has forgotten the objects. Distinguish the structure you observe in judgments, the representation you propose, and the process that uses it. Describe a comparison involving cues or task demands that could help separate knowledge from control.

Conclude with the limits of your account: what would you need to know about the materials, community, learning history, and task before generalizing it? The readings support several ways to constrain an explanation, not one formula for every concept.

For the selection and coordination of information during a task, continue to How Do We Direct Attention and Control Thought?. For the retention and retrieval of knowledge, see How Do We Remember—and Why Do We Forget?.

To examine how knowledge supports words, sentences, connected discourse, and conversation, continue to How Do We Understand and Use Language?.