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Discovering Psychology: Updated Edition

The Developing Child

The Developing Child is the fifth program in the Discovering Psychology series. This program introduces examples of cognitive, perceptual, and behavioral development in children. You'll explore the roles of heredity and environment in child development, and children's incremental understanding of such phenomena as object permanence, symbolic reasoning, and perception of visual depth.

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Interview Excerpt: Judy Deloache on Symbolic Reasoning

Researcher Judy Deloache describes how children’s recognition of scale models as representations reflects development of symbolic reasoning.

One of the most distinctive human characteristics is the ability to understand and use symbols. We have a variety of symbol systems in our everyday lives. We use language, we read, we use pictures, and we understand computer programs. We’re not born with this ability, so what I’m studying are the earliest forms of symbolic reasoning that a child understands, and when that cognitive ability to reason develops.

Specifically, I’m concerned with a child’s understanding of a scale model, a symbol, that represents a larger space. When the child sees the scale model of a miniature playroom, does the child understand that this little playroom represents a bigger room? And when does a child acquire symbolic understanding? The interesting feature of this research is that we see an abrupt change between ages two-and-a-half and three in a child’s ability to understand scale models. When we experiment with scale models of playrooms, the two-and-a-half-year-old doesn’t understand the relationship between the symbolic room and the actual room, and instead treats it as a separate object. The three-year-old, on the other hand, understands immediately that the model is a symbol for an actual room.

In becoming symbolic creatures, we learn to think abstractly. At age three, children acquire the ability to think about things in two different ways at the same time: as both an object and a symbol for something else. Acquiring symbolic understanding is an important milestone in the cognitive development that helps us figure out how the world operates. Later in life, for example, we use it to read maps and understand languages.

This research helps us appreciate the complexity of human thought in young children. The clearer our knowledge of what children know, the better we can work with them as educators and as parents.


Behaviorism: A framework for understanding human behavior through observable, measurable data. Emphasizes objective stimulus and response over more subjective analysis of internal states. Key figures in behaviorism include American psychologists John B. Watson (1878-1958) and B.F. Skinner (1904-1990).

Depth Perception: The ability to understand the relationship among objects in space. Human beings develop a sense of depth perception as infants.

Habituation: The change in one’s response when a stimulus is presented repeatedly.

Inherited Behavioral Differences: Human characteristics, such as shyness, which may result from inherited genetic traits.

Nature Vs. Nurture Debate: The persistent controversy about whether behavior or other human characteristics are genetically predetermined, or if they are shaped predominantly by the environment and events in an individual’s life.

Object Permanence: The understanding that physical objects continue to exist even though we cannot see them; early stage in the psychological development of the child.

Symbolic Reasoning: The cognitive ability to relate one concept to another that represents it in some way. For example, a young child’s ability to reason symbolically can be tested by placing a small doll in a model room, and then asking the child to find the full-size doll in an analogous place in a normal-size room.

Volume Perception: The understanding that containers of different shapes or proportions may hold the same volume.