Understanding Psychology (10th Ed)

Conservation
of …
Modality
Change in
physical appearance
Average age
at full mastery
Number
Number of elements
in a collection
Rearranging or
dislocating elements
6–7 years
Substance
(mass)
Amount of a
malleable substance
(e.g., clay
or liquid)
Altering shape
7–8 years
7–8 years
Length
Length of a line or
object
Altering shape or
configuration
Area
Amount of surface
covered by a set of
plane figures
Rearranging the figures
8–9 years
Weight
Weight of an object
Altering shape
9–10 years
Volume
Volume of an object
(in terms of water
displacement)
Altering shape
14–15 years
FIGURE 10
These tests are frequently 
used to assess whether children have 
learned the principle of conservation 
across a variety of dimensions. Do you 
think children in the preoperational stage 
can be taught to avoid conservation 
mistakes before the typical age of 
mastery?
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408 Chapter 
12 
Development
propose that cognitive development is primarily quantitative rather than qualitative. 
They argue that although there are differences in when, how, and to what extent a 
child can use specifi c cognitive abilities—refl ecting quantitative changes, the under-
lying cognitive processes change relatively little with age (Gelman & Baillargeon, 
1983; Case & Okamoto, 1996). 
Piaget also underestimated the age at which infants and children can understand 
specifi c concepts and principles; in fact, they seem to be more sophisticated in their 
cognitive abilities than Piaget believed. For instance, some evidence suggests that 
infants as young as 5 months have rudimentary mathematical skills (Wynn, Bloom, 
& Chiang, 2002; McCrink & Wynn, 2007; van Marle & Wynn, 2009). 
Despite such criticisms, most developmental psychologists agree that although 
the processes that underlie changes in cognitive abilities may not unfold in the man-
ner Piaget’s theory suggests, he has generally provided us with an accurate account 
of age-related changes in cognitive development. Moreover, his theory has had an 
enormous infl uence in education. For example, Piaget suggests that individuals can-
not increase their cognitive performance unless both cognitive readiness brought 
about by maturation and appropriate environmental stimulation are present. This 
view has inspired the nature and structure of educational curricula and teaching 
methods. Researchers have also used Piaget’s theory and methods to investigate 
issues surrounding animal cognition, such as whether primates show object perma-
nence (they seem to; Hauser, 2000; Egan, 2005; Cunningham, 2006).