How Do Infants Build Knowledge and Skills?

From looking and listening to reaching and learning: how emerging abilities become evidence about development.

Level: Introductory
Reading load: 11 core readings in 6 units
Prerequisites: No prior course in infant development is required. The guides introduce the key terms. How Do We Develop Across the Lifespan? provides a useful broader framework; How to Read Psychological Science introduces causal inference, measurement, and replication.
Last reviewed: September 2026

Introduction

An infant's knowledge must be approached through acts that cannot yet be explained in words: a gaze held, a head turned, a reach across a gap. Each response offers evidence, though its meaning depends on the task, the child's experience, and the capacities the task requires. Success and failure can both illuminate development when we understand what produced them.

This path begins with the problem of interpreting infant behavior and an influential account of early knowledge. It then connects looking and reaching, experience-dependent perception, the learning of patterns, changes in action, and learning in social settings. A large collaborative study closes the sequence by examining variation across methods and language backgrounds. The aim is to explain emerging abilities while keeping observation, mechanism, and developmental history distinct.

By the end, you should be able to reconstruct what a task asks of an infant, compare explanations of its outcome, and propose evidence that would connect a short laboratory result to development over time. The final article is longer and more technical than the earlier studies; understanding its design and inferences does not require reproducing the statistical models.

Unit 1 of 6

How can behavior reveal infant knowledge?

Begin with the bridge between an observed response and a claim about the mind. Aslin makes that bridge explicit; Spelke and Kinzler use patterns of success and limitation to propose a structure for early knowledge. Treat their claims as questions about evidence rather than labels to attach to any infant response.

Reading
1 of 11
What’s in a Look?
Aslin, R. N. (2007). What’s in a look? Developmental Science, 10(1), 48–53. https://doi.org/10.1111/j.1467-7687.2007.00563.x
Methodological contribution · Critical reappraisal · Moderate · Full work: 6 pages
Establish the distinction the whole path will use: a measured response and the psychological interpretation placed on it. Keep the idea of a linking hypothesis available as you encounter each subsequent task.
A question to consider. If infants look equally at two events, what would you need to know before concluding that they cannot distinguish them?
Reading
2 of 11
Core Knowledge
Spelke, E. S., & Kinzler, K. D. (2007). Core knowledge. Developmental Science, 10(1), 89–96. https://doi.org/10.1111/j.1467-7687.2007.00569.x
Foundational argument · Major synthesis · Moderate · Full work: 8 pages
Use the proposed systems to formulate claims that go beyond a single task. Bring Aslin’s question about measurement to the argument from recurring signatures across ages, tasks, and species.
A question to consider. Choose one proposed system. What pattern across two different tasks would strengthen the account, and what pattern would force it to change?

Unit 2 of 6

What do looking and reaching reveal about objects?

Now examine an influential experiment and a different explanatory approach. Looking at an occluded object and perseverative reaching are not identical tests. Their comparison matters because an account of development must explain both the abilities a task reveals and the demands that can conceal or alter them.

Reading
3 of 11
Object Permanence in Five-Month-Old Infants
Baillargeon, R., Spelke, E. S., & Wasserman, S. (1985). Object permanence in five-month-old infants. Cognition, 20(3), 191–208. https://doi.org/10.1016/0010-0277(85)90008-3
Landmark empirical study · Methodological contribution · Moderate · Full work: 18 pages
Apply the linking-hypothesis approach to the drawbridge experiment. Connect its control condition to the object principles discussed by Spelke and Kinzler, while distinguishing a looking difference from a comprehensive object concept.
A question to consider. How does moving the box beside the screen help evaluate the explanation, and what further comparison would still be needed to establish where the expectation came from?
Reading
4 of 11
Development as a Dynamic System
Smith, L. B., & Thelen, E. (2003). Development as a dynamic system. Trends in Cognitive Sciences, 7(8), 343–348. https://doi.org/10.1016/S1364-6613(03)00156-6
Foundational argument · Major synthesis · Moderate · Full work: 6 pages
Introduce a process account of task performance and change. Compare the authors’ explanation of reaching with the assumptions needed to interpret the drawbridge task, without treating one as a direct replication of the other.
A question to consider. Design a change in a reaching task that would discriminate between an account based only on a fixed competence and one sensitive to recent actions and current cues.

Unit 3 of 6

How does experience tune perception and learning?

Developmental change can involve a narrowing of measured sensitivity and an increasing ability to exploit regularities. Compare changes across months in speech discrimination with learning during a brief exposure. These timescales offer different evidence about a developmental mechanism.

Reading
5 of 11
Cross-Language Speech Perception: Evidence for Perceptual Reorganization During the First Year of Life
Werker, J. F., & Tees, R. C. (1984). Cross-language speech perception: Evidence for perceptual reorganization during the first year of life. Infant Behavior and Development, 7(1), 49–63. https://doi.org/10.1016/S0163-6383(84)80022-3
Landmark empirical study · Moderate · Full work: 15 pages
Use the age and language comparisons to examine perceptual specialization. Connect their interpretation to the earlier warning that a behavioral criterion is not a direct reading of an underlying capacity.
A question to consider. Which comparison best challenges a general age-related decline in task engagement, and what would establish that particular experience contributes to the change?
Reading
6 of 11
Statistical Learning by 8-Month-Old Infants
Saffran, J. R., Aslin, R. N., & Newport, E. L. (1996). Statistical learning by 8-month-old infants. Science, 274(5294), 1926–1928. https://doi.org/10.1126/science.274.5294.1926
Landmark empirical study · Moderate · Full work: 3 pages
Examine a learning process under controlled input. Compare what exposure to a syllable stream establishes with what Werker and Tees’s developmental comparisons establish; neither design supplies the other’s evidence.
A question to consider. How could you connect this short-term learning effect to a change over infancy without assuming that a brief laboratory demonstration explains the whole developmental course?

Unit 4 of 6

How do new actions change what infants can learn?

A developing body changes both the problems an infant must solve and the experiences available to solve them. A broad review introduces these connections; an experiment then asks how specifically learning is tied to the action being performed. Cultural practices belong in this account because they shape opportunities to act.

Reading
7 of 11
Motor Development: Embodied, Embedded, Enculturated, and Enabling
Adolph, K. E., & Hoch, J. E. (2019). Motor development: Embodied, embedded, enculturated, and enabling. Annual Review of Psychology, 70(1), 141–164. https://doi.org/10.1146/annurev-psych-010418-102836
Major synthesis · Accessible · Full work: 24 pages
Broaden the dynamic-systems argument into a view of embodied, situated development. Follow one route through which a new action changes an infant’s encounters with objects or people, then distinguish that opportunity from a demonstrated downstream effect.
A question to consider. Two communities offer different opportunities for infants to move. What would you measure to study the developmental process without ranking one timetable as inherently better?
Reading
8 of 11
Specificity of Learning: Why Infants Fall Over a Veritable Cliff
Adolph, K. E. (2000). Specificity of learning: Why infants fall over a veritable cliff. Psychological Science, 11(4), 290–295. https://doi.org/10.1111/1467-9280.00258
Landmark empirical study · Moderate · Full work: 6 pages
Make the transfer question concrete through sitting and crawling. Compare a general claim about perceiving danger with an account of calibration to a particular body and action.
A question to consider. Why would successful avoidance in one posture be insufficient to predict behavior in another, and how do the individual gap thresholds make that comparison more informative?

Unit 5 of 6

Return to language with two distinct learning problems: discriminating speech sounds and linking words with possible referents. A live encounter can supply several cues at once, while information across ambiguous encounters can support learning without resolving each encounter separately. These studies examine complementary possibilities rather than a single contest between social and statistical learning.

Reading
9 of 11
Foreign-Language Experience in Infancy: Effects of Short-Term Exposure and Social Interaction on Phonetic Learning
Kuhl, P. K., Tsao, F.-M., & Liu, H.-M. (2003). Foreign-language experience in infancy: Effects of short-term exposure and social interaction on phonetic learning. Proceedings of the National Academy of Sciences, 100(15), 9096–9101. https://doi.org/10.1073/pnas.1532872100
Landmark empirical study · Moderate · Full work: 6 pages
Revisit the perceptual reorganization question through an exposure intervention. Compare learning from complex speech in live and recorded settings with learning from Saffran and colleagues’ controlled stream.
A question to consider. Why would different outcomes in these studies not establish that either social interaction or statistical regularity is the sole basis of infant learning?
Reading
10 of 11
Infants Rapidly Learn Word-Referent Mappings via Cross-Situational Statistics
Smith, L., & Yu, C. (2008). Infants rapidly learn word-referent mappings via cross-situational statistics. Cognition, 106(3), 1558–1568. https://doi.org/10.1016/j.cognition.2007.06.010
Landmark empirical study · Moderate · Full work: 11 pages
Move from recognizing sound sequences to learning relations between labels and objects. Use the ambiguous trials to identify what information accumulates, then return to Aslin’s question about what preferential looking reveals.
A question to consider. What evidence would distinguish a learned word–object association from flexible understanding of the word across new speakers, objects, and situations?

Unit 6 of 6

Which findings hold across methods and samples?

The final study returns to measurement with many laboratories investigating a common phenomenon. Ask how much of the observed variation follows the infant, the language material, or the procedure. The question is both whether an effect recurs and what its variation can teach about development.

Reading
11 of 11
Quantifying Sources of Variability in Infancy Research Using the Infant-Directed-Speech Preference
The ManyBabies Consortium. (2020). Quantifying sources of variability in infancy research using the infant-directed-speech preference. Advances in Methods and Practices in Psychological Science, 3(1), 24–52. https://doi.org/10.1177/2515245919900809
Replication · Methodological contribution · Contemporary update · Challenging · Full work: 29 pages
Use the collaborative study to revisit every earlier inference from infant behavior. Distinguish preference for infant-directed speech from the learning outcomes in the preceding unit, and compare variation within a shared protocol with differences among published studies.
A question to consider. Choose one earlier experiment and propose a multilab extension: which materials would you hold constant, which variation would you deliberately study, and which populations would make the generalization claim more informative?

Scope and omissions

This is an introduction to mechanisms of emerging knowledge and skill, concentrated on the first year and the transition into the second. Its examples connect object representation, speech perception, statistical learning, motor action, and early word learning. Speech supplies several experimentally tractable cases; it does not stand for every sensory domain.

The path does not survey prenatal development, every infant sensory system, detailed brain maturation, attachment, social evaluation, number development, or clinical assessment. Later childhood language, schooling, and reasoning also require their own treatment. Examples of early competence cannot establish the origins of a capacity on their own, and a task result is not a developmental screening tool. Many selected studies use restricted populations; the cultural discussion and collaborative study make that limitation visible without removing it.

Synthesis

An infant's growing abilities emerge through changing relations among prior sensitivities, learning, bodily capacities, and surroundings. The readings disagree about starting points and mechanisms, but make a shared demand upon explanation: it must connect an observed response with a process of development. Looking, listening, and reaching reveal different aspects of that process under different demands; no age label or single success can tell the whole story.

Choose one result and make four statements: what behavior was observed; what representation or learning process was inferred; which comparison supports that inference; and what evidence would connect it to change over time. Then name an alternative account and a new comparison that could distinguish the two. Consider whether your proposed measure would work similarly across ages and settings.

A useful developmental account must explain both continuity and change, including why learning sometimes transfers and sometimes remains specific. Shared methods and broader participation can sharpen such accounts, but more observations do not automatically settle what a measure means.

Continue with How Do Children Develop Language and Thought? to examine word learning, generalization, conceptual change, causal exploration, and developing regulation in the social settings of childhood.

For a complementary path through the organization and use of language, continue with How Do We Understand and Use Language?. To place infancy back within a whole-life perspective, return to How Do We Develop Across the Lifespan?.