Prevention Science, Vol. 5, No. 4, December 2004 (
How Early Experience Matters in Intellectual Development
in the Case of Poverty
and Clancy Blair
Experiments with rodents indicate that severe early psychological and social deprivation has
lasting detrimental effects on learning ability that are not remedied by exposure to enriching
experiences in adulthood. Findings indicate that environmental adversity early in life works to
limit the development of intelligence with consequences for later functioning. Animal experi-
ments are best viewed as supplying a rationale for early intervention in disadvantaged infants
and children who would otherwise be likely to evince low intellectual capabilities later in life.
Animal experiments conducted to date do not support an interpretation that early enrich-
ment necessarily boosts later intellectual performance beyond the normal or species-typical
range. They indicate that early intervention promotes normative development by preventing
adverse early rearing conditions from leading to negative consequences for cognitive ability
and self-regulation. The Abecedarian Project, an early enrichment intervention with infants
from economically deprived backgrounds, is presented as an example of how early experience
matters in terms of human intellectual development in disadvantaged populations. The results
of that program reﬂect what one would expect from the rodent studies mentioned above.
KEY WORDS: early intervention; intelligence; animal models.
The evidence to be reviewed in the ﬁrst section of
the paper indicates that rodents reared in “enriched”
psychological environments show better learning
ability than animals reared under psychologically
and socially impoverished circumstances. However,
there is no evidence that animals reared in so-called
enriched laboratory environments show learning
abilities beyond the normal or species-typical range.
Rather, the rodent research indicates that the en-
riched early experience averts the deterioration of
learning ability that is seen when animals are reared
This article is based, in part, on an invited presentation by the
ﬁrst author at the 2002 meeting of the American Psychological
Association, in Chicago.
Center for Developmental Science, University of North Carolina
at Chapel Hill, Chapel Hill, North Carolina.
Human Development and Family Studies, Pennsylvania State Uni-
Correspondence should be directed to Gilbert Gottlieb, Center for
Developmental Science, CB# 8115, University of North Carolina
at Chapel Hill, Chapel Hill, North Carolina 27599-8115; e-mail:
under impoverished conditions early in life. Exposure
to enriched conditions later in life is without effect in
rodents that have been severely deprived early in life.
These ﬁndings suggest that interventions with impov-
erished human populations should be instigated as
early as possible with a view to preventing intellec-
tual deterioration in such populations.
The earliest systematic study of the role of early
experience in inﬂuencing the later learning abilities
of rodents was done by Bernard Hymovitch (1952), a
doctoral student of Donald Hebb. Hymovitch reared
young rats under four conditions and then later tested
them in the very challenging Hebb-Williams maze.
The maze test consists of a series of twelve problems
in which the path between the start and ﬁnish (food)
boxes is altered from problem to problem by rear-
ranging the internal walls of the maze. This maze is
considerably more difﬁcult than a Y- or T-maze, so it
taxes the animal’s learning ability to a much greater
degree than usual maze tasks.
Hymovitch’s animals were housed individually in
(1) a stovepipe cage (which permitted little motor or
2004 Society for Prevention Research