Cognitive Development: Age 0–2

Much of modern cognitive developmental theory stems from the work of the Swiss psychologist, Jean Piaget. In the 1920s, Piaget observed that children's reasoning and understanding capabilities differed depending on their age. Piaget proposed that all children progress through a series of cognitive stages of development, just as they progress through a series of physical stages of development. According to Piaget, the rate at which children pass through these cognitive stages may vary, but boys and girls eventually pass through all the stages, in the same order.

Piaget's sensorimotor stage

During Piaget's sensorimotor stage (birth to age 2), infants and toddlers learn by doing: looking, hearing, touching, grasping, and sucking. The learning process appears to begin with coordinating movements of the body with incoming sensory data. As infants intentionally attempt to interact with the environment, infants learn that certain actions lead to specific consequences. These experiences are the beginning of the infants' understanding of cause‐and‐effect relationships.

Piaget divided the sensorimotor stage into six substages. In stage 1 (birth through month 1), infants exclusively use their reflexes, and their cognitive capabilities are limited. In stage 2 (months 1 through 4), infants engage in behaviors that accidentally produce specific effects. Infants then repeat the behavior to obtain the same effect. An example is the infant's learning to suck on a pacifier following a series of trial‐and‐error attempts to use the new object. In stage 3 (months 4 through 8), infants begin to explore the impact of their behaviors on the environment. In stage 4 (months 8 through 12), infants purposefully carry out goal‐directed behaviors.

Object permanence, or the knowledge that out‐of‐sight objects still exist, may begin to appear at about month 9 as infants search for objects that are hidden from view. In stage 5 (months 12 through 18), toddlers explore cause‐and‐effect relationships by intentionally manipulating causes to produce novel effects. For example, a toddler may attempt to make her parents smile by waving her hands at them. In stage 6 (months 18 through 24), toddlers begin to exhibit representational (symbolic) thought, demonstrating that they have started to internalize symbols as objects, such as people, places, and things. The child at this stage, for instance, uses words to refer to specific items, such as milk, dog, papa, or mama.

Piaget's model introduces several other important concepts. Piaget termed the infant's innate thinking processes as schemas. In the sensorimotor period, these mental processes coordinate sensory, perceptual, and motor information so that infants eventually develop mental representations. In other words, reflexes provide the basis for schemas, which in turn provide the basis for representational thinking. For example, a child repeatedly touches and sees its rattle and thus learns to identify the rattle by forming an internalized image of it.

According to Piaget, cognitive development occurs from two processes: adaptation and equilibrium.

Adaptation involves children changing their behavior to meet situational demands and consists of two subprocesses: assimilation and accommodation.

  • Assimilation is the application of previous concepts to new concepts, such as a child who refers to a whale as a fish.

  • Accommodation is the altering of previous concepts in the face of new information, such as a child who discovers that some creatures living in the ocean are not fish and then correctly refers to a whale as a mammal.

Equilibrium is Piaget's term for the basic process underlying the human ability to adapt—is the search for balance between self and the world. Equilibrium involves the matching of children's adaptive functioning to situational demands, such as when a child realizes that he is one member of a family and not the center of the world. Equilibrium, which helps remove inconsistencies between reality and personal perspectives, keeps children moving along the developmental pathway, allowing them to make increasingly effective adaptations and decisions.

Evaluating Piagetian theory

The majority of researchers today accept Piaget's primary tenet: New cognitive skills build upon previous cognitive skills. Researchers see infants and toddlers as active learners who purposefully see, touch, and do, and who consequently develop additional cognitive skills. Developmentalists see cognitive development as involving both advancement and limitation. Devlopmentalists also applaud Piaget's role in stimulating professional interest in the cognitive world of children.

Piaget's research and theories are not unchallenged, however. Some of the more prominent critics of Piaget include Robbie Case, Pierr Dasen, Kurt Fischer, and Elizabeth Spelke. These critics and others maintain that the stages of development described by Piaget are not so distinct and clearly defined as Piaget originally indicated. These detractors also note that all children do not necessarily pass through Piaget's stages in precisely the same way or order. Piaget was aware of this phenomenon, which he termed decalage, but he never adequately explained decalage in light of the rest of his model.

Critics also suggest that toddlers and preschoolers are not as egocentric or as easily deceived as Piaget believed. Preschoolers may empathize with others, or put themselves into another person's shoes, and young children may make inferences and use logic. Preschoolers also develop cognitive abilities in relation to particular social and cultural contexts. These abilities may develop differently within enriched or deprived cultural environments. In other words, children who grow up in middle and upper‐class families may have more opportunities to develop cognitive skills than those who grow up in lower‐class families.

Children appear to employ and more deeply understand symbols at an earlier age than was previously thought. In as early as the first 3 months, infants display a basic understanding of how the world works. For example, infants pay closer attention to objects that seem to defy physical laws, such as balls that appear to roll through walls or rattles that appear to hang in mid‐air as opposed to stationary objects.


Central to early cognitive development is memory development. Memory is the ability to encode, retain, and recall information over time. Researchers generally refer to sensory (less than 1 second), short‐term (less than 30 seconds), and long‐term (indefinite) memory stores. Children are not able to habituate or learn if they are unable to encode objects, people, and places and eventually recall them from long‐term memory.

Researchers are unclear about the exact nature of infantile memory, however. The unclear facts about infantile memory include how long such memories last, as well as how easily memories are retrieved from long‐term stores. Evidence suggests that babies begin forming long‐term memories during the first 6 months. Infants may recognize and remember primary caretakers, as well as familiar surroundings. Early memory experiences help infants and toddlers to understand basic concepts and categories, all of which are central to more completely understanding the world around them.


Language skills begin to emerge during the first 2 years. Psycholinguists, specialists in the study of language, indicate that language is an outgrowth of children's ability to use symbols. Physical development determines the timing of language development. As the brains develop, preschoolers acquire the capacity for representational thinking, which lays the foundation for language. In this way, cognitive development also determines the timing of language development. Observational learning (imitation) and operant conditioning (reinforcement) play important roles in the early acquisition of language. Children are reinforced to speak meaningfully and reasonably by imitating the language of their caregivers; in turn caregivers are prompted to respond meaningfully and reasonably to the children.

Psycholinguists are especially interested in three elements of language: content (what is meant), form (what is actually said), and use (how and to whom it is said). Psycholinguists claim that all members of the human race use these three elements in some combination to communicate with each other. Noam Chomsky suggested that the learning of a language is rooted in an inborn capacity to comprehend and structure language, which he defined as the language acquisition device.

According to psycholinguists, acquisition of language also occurs within a social and cultural context. Socializing agents—family members, peers, teachers, and the media—teach children how to think and act in socially acceptable ways. Children learn about the world and society as they learn to use language.

Infants and toddlers understand language before actually speaking language; children have receptive language, or an understanding of the spoken and written word, before acquiring productive language, or an ability to use the spoken or written word. Before saying their first words, infants babble. That is, babies make meaningless sounds while learning to control their vocalizations. By the end of the first year, most babies are uttering single words. Soon infants begin to use holophrastic speech, or single words that convey complete ideas. “Mama” (meaning “Mama, come here!”) and “Milk!” (meaning “Give me some milk!”) are examples of holophrastic speech. When starting to put words together to form sentences, children first use telegraphic speech, in which words that are the most meaningful are used, such as “Want milk!”