Why Do the Achievement Gaps Exist?
Part of the problem in determining "how much" of the black-white achievement gap results from heredity versus environment is that a person's genes and environment influence each other in complicated ways. It is often difficult to tell what part of a person's situation is influenced by their genetic makeup and what part is shaped by their environment.
This reports some of the ideas and findings from the following source:
Phillips, M., Brooks-Gunn, J., Duncan, G. J., Klebanov P., & Crane, J. (1998). Family background, parenting practices, and the black-white test score gap. In C. Jencks and M. Phillips (Eds.),The black-white test score gap(pp. 103-145). Washington, DC: Brookings Institution.
To see other reports that originated from this same citation, go to the bibliography.
Scholars Meredith Phillips, Jeanne Brooks-Gunn, Greg J. Duncan, Pamela Klebanov, and Jonathan Crane study the effects of families on black and white children's test scores. However, because families share genes as well as home environments, it is important to try to determine the relative importance of each of these influences.
What makes this particularly difficult, say Phillips and her coauthors, is that genetic effects can often appear to be environmental. Before examining how a child's heredity and environment affect their test scores, it makes sense to look at how heredity and environment relate to each other.
Following the work of researchers Robert Plomin, J.C. DeFries, and John Loehlin, Phillips and her colleagues identify three ways that a child's heredity and environment may be correlated:
The authors argue that because genes and environment may be correlated, or related, in these ways, genetic effects can sometimes appear to be the result of environmental influences.
Parent's genes can influence both a child's environment and heredity.
For instance,very smart parents may enjoy reading more to their child than parents of average intelligence because a parent's genes affect their reading skills. They read better and so they enjoy reading more. If parents who read more to their children have children with higher vocabulary scores, then we have to ask:
It is difficult to decide. Because parents' genetic makeup affects both a child's genetic makeup and his or her environment, it is difficult to tell what the real cause is—or, how the causes work together. See Figure 1.
It makes a difference which way we answer the question. For instance, imagine that a school begins a program to encourage parents to read to their children. If the main influence on the child's vocabulary scores is environmental, we would expect children's vocabulary scores to rise. If, on the other hand, the main influence on the child's vocabulary scores was hereditary, we would not expect children's vocabulary scores to rise that much.
The authors say that a child's genetic makeup can also affect the environment that the child seeks out. For instance, if children's genes affect how much they enjoy being read to, then the fact that they respond positively to being read to could motivate their parents to read to them more often. In this situation, a child's genetic ability to pick up new words would be the cause of parents' reading (not the other way around). See Figure 2.
If a child's vocabulary and parents' reading were related in this way, then encouraging parents to read more to their children would not raise children's vocabulary scores as much.
Phillips and her colleagues say that a person's genes may have nothing to do with innate cognitive ability, but they may still influence how well he or she achieves academically. That is, if persons' genetic makeup influences the way that they look, and they are treated by others differently because of the way that they look, this can affect their academic achievement. For instance, because black skin and facial characteristics are important social signals in American society, black people may be systematically discriminated against (for instance, they may go to poorer schools or get less well paying jobs). In this circumstance, genetic differences between black and white Americans certainly makes a difference, but not because of cognitive differences between the two groups.
In this circumstance a child's environment "sorts" him or her into different environmental situations. Some situations foster high vocabulary. Some situations do not. What is important, though, is that the "sorting" mechanism has less to do with cognitive ability than with another (irrelevant) genetic characteristic. See Figure 3.
In this situation, white children may be sorted into schools that encourage parents to read to their children while black children are sorted into schools that do not encourage parents to read to their children.
After laying out the challenges to teasing out the relative influences of heredity and family environment on the black-white test score gap, Phillips and her colleagues attempt to move ahead and determine just how much influence family characteristics have on test scores.
What is the effect of family characteristics on the black-white test score gap?
What are the relative effects of small children's heredity versus their environment on their vocabulary scores?
Phillips and her colleagues draw their data from two sources:
Phillips and her colleagues sought to determine the relative importance of a wide range of family characteristics for children's vocabulary test scores. They did this by running statistical models in which they would factor in different influences and examine how the included variables changed the differences in black and white children's test scores.
This research was funded, in part, by the Mellon Foundation, the Spencer Foundation, and the National Institute for Child Health and Human Development's Research Network on Child and Family Well-being.
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