Piaget and Kohlberg: Developmental Psychology Theories

Introduction to Developmental Psychology

Developmental psychology draws on a range of theoretical frameworks to explain how human beings grow cognitively, morally, and socially from infancy through adulthood. Two of the most influential contributors to this field are Jean Piaget, whose theory of cognitive development maps the stages through which children acquire and use knowledge, and Lawrence Kohlberg, whose theory of moral development charts how children come to reason about right and wrong. Kohlberg's work builds directly on Piaget's earlier moral framework, making the two theories closely linked and mutually illuminating. This paper examines both theories in turn, outlining Piaget's four stages of cognitive development and Kohlberg's three-level, six-stage model of moral reasoning.

Piaget's Four Stages of Cognitive Development

Jean Piaget developed the theory of cognitive development, which suggests there are four key stages through which children advance as their minds mature. The theory focuses largely on understanding the nature of knowledge and intelligence, and how children acquire and apply both. Piaget argues that cognitive development is central to human development as a whole, and that language skills depend on cognitive development (Fiore, 2011, p. 35).

Sensorimotor and Preoperational Stages

The first stage of development is the sensorimotor stage, which spans from birth to approximately 24 months. During this period, the child begins to know the world through sensations and actions. As Piaget (1983, p. 152) describes, assimilation is the process whereby children encounter the environment and process new information using pre-existing knowledge. For example, when a child sucks their thumb for the first time and gains pleasure from the action, they may intentionally repeat it. Accommodation, on the other hand, occurs when children alter pre-existing schemas in order to understand new information (Piaget & Inhelder, 1973, p. 31).

During this stage, infants learn that objects continue to exist even when they are out of view — a phenomenon known as object permanence. They also learn to differentiate objects from people and begin to realize that their actions have consequences, which they come to understand through the interrelated processes of assimilation and accommodation (Rathus, 2011, p. 17). A characteristic example is when a child tries different sounds to attract a caregiver's attention and learns, from the caregiver's response, which sound is most effective.

The second stage is the preoperational stage, spanning ages 2 to 7 years. At this stage, the child begins to think symbolically and uses pictures and words to represent and express ideas. Piaget and Inhelder (1973) argue that children at this stage are often egocentric, meaning they can only see objects and people from their own point of view and find it difficult to adopt another person's perspective (p. 37–38). Role-playing is central to this stage: children mimic and imitate the behavior of parents and caregivers as a means of acquiring language and social understanding. A typical example is a child using a stick as a pretend horse or treating an everyday object as a toy car.

Kohlberg's Theory of Moral Development

Children in this stage use inductive reasoning to move from specific observations to general principles. For instance, a child can reason that her pet is a poodle, a poodle is a dog, and dogs are animals. As Rathus (2008, p. 23) notes, children at this stage "can focus on multiple parts of a problem at once," allowing them to perceive objects and situations from more than one point of view.

The fourth and final stage is the formal operational stage, beginning around age 12 and continuing into adulthood. During this stage, adolescents become capable of abstract thought — reasoning that does not require reference to concrete objects (Brain & Mukherji, 2005, p. 77). They also develop the capacity to use reason when solving problems and to reflect on moral, political, philosophical, and social questions. Deductive reasoning emerges at this stage, enabling individuals to "consider past experiences, present demands, and future consequences in attempting to maximize the success of his or her adaptation to the world" (Salkind, 2004, p. 107).

Lawrence Kohlberg presents six moral development stages that children progress through. These six stages are essentially an extension of Piaget's earlier two-stage process of moral development (Fiore, 2011, p. 168). Piaget's two-stage theory groups children by age, arguing that children below age 10 reason about moral dilemmas according to a fixed set of rules provided by adults and God, while those above this age understand that rules may sometimes be adjusted depending on the situation (Piaget, 1932, p. 137).

Kohlberg's theory is based on research with groups of children to whom he presented a series of moral dilemmas, then interviewed them in order to analyze their reasoning processes (Kohlberg, 1973, p. 632). His focus was not on the final decision reached but on the thought process that led to it. Using these experiments — most famously the dilemma of "Heinz steals the drug" — he developed three levels of moral development: pre-conventional, conventional, and post-conventional morality, each containing two stages (Kohlberg, 1973, p. 641).