How Logical Reasoning Changes With Age

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Tweens experience a variety of cognitive changes, including an increase in logical thinking. According to the American Psychological Association, children between the ages of about 7 and 12 develop more concrete logic and problem-solving skills in three main ways: conservation, classification, and reversibility. The cognitive processes of older tweens, in particular, transition from child-like reasoning to a more adult-like way of thinking, which is increasingly complex and abstract.

Conservation: Outward Appearance Less Important

Eminent psychologist Jean Piaget (1896-1980) theorized that until around age 6, children lack a clear understanding of how two things with different outward appearances might actually be the same.

In a classic study, Piaget poured liquid from a tall, thin glass into a thick, short glass right in front of their eyes. Younger children thought the liquid became a smaller amount simply because the liquid's outward appearance changed. In other words, the perception was that shorter equals less. As children develop their reasoning skills, they eventually understand that the amount of liquid doesn't change.

Younger children tend to focus on only one feature of a problem at a time.

Younger children will think that the amount of liquid changed because they were only paying attention to the height or the width of the glass, not both. However, as children learn to mentally manipulate information, they can understand that the shorter height is made up for by the thicker glass, therefore, providing the same amount of space overall. By the time they are tweens, they are able to imagine various hypothetical scenarios with containers of all shapes and sizes.

The ability to consider multiple features at once extends well beyond the physical world. For example, as tweens start to develop more abstract reasoning skills, it allows them to grasp complex social dilemmas that have multiple pros and cons. They also begin to think hypothetically and can see how an action by one person or group could offset an action made by another.

Classification: Categorizing by Similar Properties

Children become highly skilled at categorizing people and objects—another development in logical reasoning. They also realize that hierarchies of groupings exist. For example, they know that "animals" can be divided into groups including "mammals" and "reptiles." They also know the mammal group can be further broken down into types of mammals like "dogs" and "leopards."

Children can grasp that there is always a greater quantity of objects within a broad category (such as "animal") than there are in a specific category (such as "dog").

As children approach adolescence, they will learn to apply what they have learned from these classifications and make generalizations and logical inferences. For instance, they will know that a "chair" will float or burn because it is made of "wood."

While these concepts seem obvious to most adults, understanding them is a major step forward in a child's cognitive development. The ability to make logical inferences paves the way for more advanced comprehension of science and math, as well as the complex language skills and perspective required for more meaningful social interactions.

Reversibility: Things Can Change Back to Original Form

A final key logical reasoning development for children is understanding the concept of reversibility. Reversibility refers to how things can be altered and changed back to their original state.

One simple example that kids understand early on is that you can roll a ball of clay into a long snake (conservation), then roll it back into a ball (reversibility) without changing its internal properties.

Later, children will be able to understand more complex ideas about reversibility and irreversibility. For example, water can be frozen and then thawed, but eggs cannot be unscrambled.

A full understanding of the consequences of reversibility continues to develop from early childhood into adolescence. For example, young children begin to learn reversibility when solving simple math problems. They learn that 5 + 3 = 8 and 8 – 5 = 3. This later evolves into more complex math problems with division and multiplication such as 12 x 5 = 60 and 60 / 5 = 12.  

This concept of reversibility is built upon throughout their education, and by the time they are tweens, they are solving higher-order math and science problems as compared to their younger counterparts. For example, they learn to solve for 'x' in algebraic equations.

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