Invitation to Psychology

ChapTer 3 Development Over the Life Span 91

become capable of abstract reasoning and enter

the formal operations stage. They are able to rea-

son about situations they have not experienced

firsthand, and they can think about future pos-

sibilities. They are able to search systematically

for solutions to problems. They are able to draw

logical conclusions from premises common to

their culture and experience.

explore the concept Piaget’s Stages of

Cognitive Development at MyPsychLab

Current Views of Cognitive

Development Lo 3.8

Piaget’s central idea has been well supported:

New reasoning abilities depend on the emer-

gence of previous ones. You cannot learn algebra

before you can count, and you cannot learn

philosophy before you understand logic. But

since Piaget’s original work, the field of develop-

mental psychology has undergone an explosion

of imaginative research that has allowed investi-

gators to get into the minds of even the youngest

infants. The result has been a major modifica-

tion of Piaget’s ideas. Here’s why.

glass, preoperational children will say there is more
liquid in the second glass. They attend to the ap-
pearance of the liquid (its height in the glass) to
judge its quantity, and so they are misled (see
Figure 3.2).
From the ages of 7 to about 12, Piaget said,
children increasingly become able to take other
people’s perspectives and they make fewer logi-
cal errors. Piaget called this the concrete operations
stage because he thought children’s mental abilities
are tied to information that is concrete, that is, to
actual experiences that have happened or concepts
that have a tangible meaning to them. Children at
this stage make errors of reasoning when they are
asked to think about abstract ideas such as “patrio-
tism” or “future education.” During these years,
nonetheless, children’s cognitive abilities expand
rapidly. They come to understand the principles
of conservation and cause and effect. They learn
mental operations, such as basic arithmetic. They
are able to categorize things (for example, oaks as
trees) and to order things serially from smallest to
largest, lightest to darkest, and shortest to tallest.
Finally, said Piaget, beginning at about age
12 or 13 and continuing into adulthood, people

FiGure 3.2 Piaget’s Principle of Conservation
In one test for conservation of size (left), the child must say which is bigger—a round lump of clay or the same
amount of clay pressed flat. Preoperational children think that the flattened clay is bigger, because it seems to take
up more space. In a test for conservation of quantity (right), the child is shown two short glasses with equal amounts
of liquid. Then the contents of one glass are poured into a tall, narrower glass, and the child is asked whether one
container now has more. Most preoperational children do not understand that pouring liquid from a short glass into a
taller one leaves the amount of liquid unchanged. They judge only by the height of the liquid in the glass.

Get Involved! a Test of Conservation

If you know any young children, try one of Piaget’s conservation experiments. A simple one is to make two

rows of seven buttons or pennies, aligned identically. Ask the child whether one row has more. Now simply

spread out the buttons in one of the rows, and ask the child again whether one row has more. If the child

says, “Yes,” ask which one and why. Try to do this experiment with a 3-year-old and a 7- or 8-year-old. You

will probably see a big difference in their answers.