Intellectual (Cognitive) Development — Piaget & Kohlberg
What Is Intellectual Development?
Intellectual development, also called cognitive development, is about how the mind grows. It covers memory, concentration, reasoning, problem-solving, language acquisition, and the ability to think in abstract terms. Like physical development, cognitive development follows a broadly predictable sequence — but theorists such as Jean Piaget and Lawrence Kohlberg have given us specific frameworks to describe how thinking changes at each life stage.
In health and social care, understanding cognitive development helps practitioners communicate appropriately. A support worker in a nursery setting needs to know that a 3-year-old thinks very differently from a 10-year-old. A mental health nurse working with an older adult needs to understand what normal age-related memory change looks like — and what might indicate dementia.
Piaget’s Four Stages of Cognitive Development
Jean Piaget (1896–1980) was a Swiss psychologist who argued that children move through four distinct stages of cognitive development. Each stage represents a qualitatively different way of thinking — not just knowing more, but thinking in a fundamentally different way. Piaget called the mental frameworks through which we interpret the world schemas. As children encounter new experiences that don’t fit existing schemas, they either assimilate the new information or adapt their schemas to accommodate it.
Piaget’s four cognitive development stages, in order: sensorimotor (birth–2 years), pre-operational (2–7 years), concrete operational (7–11 years), formal operational (12 years+). Questions often ask you to name the stage AND describe one feature of it.
In the sensorimotor stage, infants learn about the world through their senses (sight, touch, taste, sound, smell) and through physical actions — reaching, grasping, mouthing objects. Thinking at this stage is tied entirely to what is immediately present and perceived. A key milestone Piaget identified is object permanence — the understanding that objects continue to exist even when out of sight. This typically develops at around 8–12 months. Before object permanence, an infant will not search for a toy hidden under a cloth; after it, they will.
In the pre-operational stage, children develop language rapidly and begin to use symbols (words and images) to represent objects. However, their thinking has important limitations. It is egocentric — the child cannot easily take another person’s viewpoint. A child in this stage will assume that because they can see something, everyone else can see it too. Piaget also noted that pre-operational children lack conservation — the understanding that quantity stays the same even when appearance changes. For example, a child in this stage will say there is “more water” in a tall thin glass than in a short wide one, even when told the same amount was poured.
In the concrete operational stage, children can now think logically, but only about concrete, real-world events they can observe directly — not about hypothetical or abstract situations. They master conservation, can sort objects by multiple criteria (e.g. size and colour), and understand that actions can be reversed (reversibility). Children at this stage can follow instructions in a step-by-step way and solve practical problems, making this stage important for understanding school-age learning.
In the formal operational stage, the individual can now think abstractly — about hypothetical situations, ideals, and possibilities that don’t exist in front of them. They can reason systematically (like a scientist testing a hypothesis), consider multiple viewpoints simultaneously, and form their own values and beliefs. This stage maps onto adolescence and continues into adulthood. Not all adults reach or consistently use formal operational thinking in all contexts.
Kohlberg’s Three Levels of Moral Development
Lawrence Kohlberg (1927–1987) built on Piaget’s work to describe how moral reasoning develops across the lifespan. He presented people with moral dilemmas (including the famous “Heinz dilemma”, in which a man must decide whether to steal a drug to save his wife’s life) and studied the reasons they gave for their answers, not just the answers themselves. Kohlberg identified three levels of moral development, each divided into two stages.
Kohlberg’s three levels of moral development are: pre-conventional (self-interest and consequences), conventional (rules, authority, social order), and post-conventional (abstract ethical principles). Most children operate at pre-conventional; most adults at conventional; a minority reach post-conventional.
Pre-Conventional Morality (Kohlberg’s first level) is typical of young children. Moral decisions are based on self-interest: behaviour is right if it avoids punishment or gains a reward. A child at this level might say stealing is wrong because they would get into trouble — not because it harms another person.
Conventional Morality (Kohlberg’s second level) is typical of older children, adolescents, and most adults. The individual follows rules because they value social order, the approval of others, and the expectations of family, peers, and society. Doing what is “right” means following the law, being a good friend, or meeting social expectations.
Post-Conventional Morality (Kohlberg’s third level) involves reasoning beyond rules and social approval. The individual recognises that laws can be unjust and applies universal ethical principles (such as justice, human dignity, equality) even when they conflict with social rules. Kohlberg believed this level is reached by only a minority of adults. A health worker who challenges an unethical policy on principle is demonstrating post-conventional reasoning.
Cognitive Development in Later Adulthood
Piaget’s framework does not describe specific changes in later adulthood — his stages are complete by adolescence. However, cognitive changes do occur as people age. Processing speed typically slows, and episodic memory (recall of recent events) is often the first to decline. Acquiring new knowledge and learning new skills remains possible throughout later adulthood, though it may take longer. Maintaining mental stimulation through reading, puzzles, social interaction, and learning new activities is linked to better cognitive outcomes.