Are children whose parents or older siblings have exhibited reading problems at greater risk for reading difficulties than are other children of otherwise similar backgrounds? Decades of research on the familial aggregation of reading problems suggest that this is so.
Factors identified as family risk factors include family history of reading problems, home literacy environment, verbal interaction, language other than English, nonstandard dialect, and family-based socioeconomic status (SES). It is important to bear in mind, however, that family patterns of reading problems can be attributed either to shared genetic or to shared environmental factors.
If a child is diagnosed with a reading disability, there is a higher than normal probability that other family members will also have difficulties with reading (see Finucci et al., 1976; Hallgren, 1950; Gilger et al., 1991; Vogler et al., 1985). The exact probability seems to depend on a variety of factors, including the severity of the child’s reading disability.
Furthermore, when the parents’ diagnosis for reading disability is based on self-report, the family incidence tends to be lower than when the diagnosis is based on the direct measurement of parents’ reading skills (Gilger et al., 1991).
Most studies of familial incidence first diagnose a child with reading disability using a severity criterion that would identify 5 to 10 percent of children who have normal intelligence and have had what for the majority of children is effective education.
The investigators then attempt to use a similar severity criterion to diagnose reading disability in the parents. Evidence for the family nature of reading disability is based on parental rates that are substantially above the 5 to 10 percent rate estimated for the population. Scarborough (1998) computed the average rate of reading disability among parents across eight family studies that included a total of 516 families. The rate across studies varied from 25 to 60 percent, with a median value of 37 percent.
Thus, all studies found rates for reading disability among parents of reading-disabled children that were considerably higher than expected in the normal population. The median proportion of reading disability among fathers (46 percent) was slightly higher than the median proportion among mothers (33 percent).
A few studies have attempted to estimate the prospective risk to the child when parental disabilities are identified first (Finucci et al., 1985; Fowler and Cross, 1986; Scarborough, 1990). Those prospective studies clearly show that parents’ reading disabilities predict a higher than normal rate of reading disabilities in their children (31 to 62 percent versus 5 to 10 percent).
Although parental reading disabilities are not completely predictive of their children’s reading disabilities, the substantially greater risk at least warrants very close monitoring of their children’s progress in early language and literacy development. Results from two predictive studies (Elbro et al., 1996; Scarborough, 1989, 1990, 1991) suggest that whether these children develop reading problems can be predicted from preschool measures of language and literacy skills.
If so, it would be potentially affordable to assess that small subset of the population a year or two before kindergarten and to provide intervention to those with the weakest skills. Of course, to do so would require an effective means of persuading parents with a history of reading problems to step forward so that this service could be provided for their offspring. This sort of recruitment program has never been attempted, so its feasibility is unknown.