326 CHAPTER 8
The infants tested in this study ranged from 6 to 14 months in age. They were placed
on the middle of the table and then encouraged (usually by their mothers) to crawl over
either the shallow side or the deep side. Most babies—81 percent—refused to crawl over
the deep side, even though they could touch it with their hands and feel that it was solid.
They were upset and seemed fearful when encouraged to crawl across. Gibson and Walk
interpreted this as a very early sign of the concept of depth perception.Questions for Further Discussion- Does the fact that 19 percent of the infants did crawl over the deep side of the visual
cliff necessarily mean that those infants could not perceive the depth? - What other factors might explain the willingness of the 19 percent to crawl over the
deep side? - Are there any ethical concerns in this experiment?
- Ducks aren’t bothered by the visual cliff at all—why might that be?
Cognitive Development
- 7 Compare and contrast two theories of cognitive development, and define
autism spectrum disorder.
By the time the average infant has reached the age of 1 year, it has tripled its birth
weight and added about another foot to its height. The brain triples its weight in the
first 2 years, reaching about 75 percent of its adult weight. By age 5, the brain is at
90 percent of its adult weight. This increase makes possible a tremendous amount of
major advances in cognitive development, including the development of thinking,
problem solving, and memory.
PIAGET’S THEORY: FOUR STAGES OF COGNITIVE DEVELOPMENT One of the three
ways of examining the development of cognition that we will discuss in this chapter
is found in the work of Jean Piaget. Early researcher Jean Piaget developed his theory
from detailed observations of infants and children, most especially his own three chil-
dren. Piaget made significant contributions to the understanding of how children think
about the world around them; his theory shifted the commonly held view that chil-
dren’s thinking was that of “little adults” toward recognition that it was actually quite
different from adult thinking. Piaget believed that children form mental concepts or
schemes as they experience new situations and events. For example, if Sandy points to
a picture of an apple and tells her child, “that’s an apple,” the child forms a scheme for
“apple” that looks something like that picture. Piaget also believed that children first
try to understand new things in terms of schemes they already possess, a process called
assimilation. The child might see an orange and say “apple” because both objects are
round. When corrected, the child might alter the scheme for apple to include “round”
and “red.” The process of altering or adjusting old schemes to fit new information and
experiences is accommodation (Piaget, 1952, 1962, 1983).
Piaget also proposed that there are four distinct stages of cognitive develop-
ment that occur from infancy to adolescence, as shown in Ta b l e 8. 3 (Piaget, 1952, 1962,
1983).
THE SENSORIMOTOR STAGE The sensorimotor stage is the first of Piaget’s stages. It con-
cerns infants from birth to age 2. In this stage, infants use their senses and motor abilities
to learn about the world around them. At first, infants only have the involuntary reflexes
present at birth to interact with objects and people. As their sensory and motor develop-
ment progresses, they begin to interact deliberately with objects by grasping, pushing,
tasting, and so on. Infants move from simple repetitive actions, such as grabbing their
toes, to complex patterns, such as trying to put a shape into a sorting box.
cognitive development
the develoRment of thinMing RroDlem
solving and memory.
schemes
in this case a mental conceRt
formed through eZReriences with
oDLects and events.
sensorimotor stage
2iagetos first stage of cognitive devel-
oRment in which the infant uses its
senses and motor aDilities to interact
with oDLects in the environment.