The Relative Value of Reading Ability and IQ as Predictors of Teacher-Reported Behavior Problems
of age, sex, and verbal IQ were controlled in the analysis of the data. Thus, the predictive significance of IQ for behavior problems may be a consequence of the confounding effects of reading disability, or vice versa. Furthermore, since levels of family Warren R. Stanton, Michael Feehan, Rob McGee, adversity are related to both IQ (Stanton, McGee, & Silva, 1989) and reading abiliand Phil A. Silva ty (McGee, Williams, & Silva, 1988), the reported relationships between low IQ scores, poor reading ability, and problem behavior could be accounted for by the Measures of early family adversity, pre-school-age IQ, school-age IQ, and reading ability were obtained from 779 Dunedin children. The data were used to examineeffects of family adversity. That is, after controlling for the effects of an adverse the role of reading ability in the relationship between intellectual performance and teacher-reported behavior problems. Results of regression analyses showed thatfamily background, there may be no evifamily adversity and pre-school-age IQ predicted problem behavior during the firstdence of the reported relationship beyear at school. However, reading scores accounted for a larger proportion of thetween reading, IQ, and problem behavior. Therefore, the aim of the present study variance in the later behavior problem scores than did school-age IQ scores, and was to examine the relative value of meawhen reading ability was entered in the regression equation before IQ, then reading but not IQ significantly predicted change in problem behavior during the primarysures of family adversity, reading, and IQ as predictors of problem behavior and school years. The results indicated that the association between IQ scores and probhence their relevance to models of problem behavior was mediated by reading ability and that a measure of school-age IQ lem behavior. has limited usefulness for models of primary school-age problem behavior.
R
eading ability and performance on IQ tests have been independently associated with the development of behavioral problems in childhood and early adolescence. Evidence to support a relationship between low IQ and behavioral problems was reported by Rutter, Tizard, and Whitmore (1970) in the Isle of Wight Study, and by McGee, Silva, and Williams (1983) in Dunedin, New Zealand. Hirschi and Hindelang (1977) reviewed the role of cognitive ability in the development of delinquency and concluded that lower intellectual performance is related to delinquent behavior through its effect on school performance. Similarly, others have reported a relationship between attention deficit disorder (ADD) or hyperactivity and IQ (August & Stewart, 1982; Schachar, Rutter, & Smith, 1981; Werry, Elkind, & Reeves, 1987). A link between reading difficulties and behavioral problems has been suggested by a number of researchers, including Carlson, Lahey, and Neeper (1986), McMichael (1979), Rutter et al. (1970), and Sturge (1982). Using the Rutter questionnaire, McGee et al. (1983) found that reading ability was significantly lower in groups of children with behavioral problems identified by the teacher alone, and by both parent and teacher, compared to the groups identified by parents only and 514
the remainder of the sample. Kavale, Alper, and Purcell (1981) suggested that reading disorder in children is strongly associated with teachers' judgments of behavior problems. However, reading ability and IQ have been shown to be significantly correlated. For example, Sattler (1982) reported a correlation of 0.6 for Wechsler Intelligence Scale for Children-Revised (WISCR) (Wechsler, 1974) Full Scale IQ scores and reading skills scores of the Wide Range Achievement Test (WRAT) (Jastak & Jastak, 1976). Share and Silva (1986) found that scores on the Burt Word Reading Test (Scottish Council for Research in Education, 1976) correlated with both the WISC-R Full Scale IQ scores (0.58) and the Performance IQ scores (0.42) administered at age 11 years. There is also evidence that changes in IQ scores can result from success in learning to read (Bishop & Butter worth, 1980; Share, McGee, & Silva, 1989). Few studies have examined the degree to which reading ability and IQ are related to problem behavior when the effect of the other is controlled in the analysis. Werry et al. (1987) reported a significant difference in reading scores between attention deficit disorder and conduct disorder groups and a control group, which persisted when the effects
METHOD Sample The sample consisted of children enrolled in the Dunedin Multidisciplinary Health and Development Study (DMHDS). They were part of a cohort born at the Queen Mary Maternity Hospital, Dunedin, between April 1, 1972, and March 31, 1973. A more detailed description of the sample is given by Silva (in press). In summary, the DMHDS is a longitudinal study of the health, development, and behavior of a cohort of New Zealand children. When the children were age 3 years, 1,139 were found to be living in Otago province. One thousand and thirty-seven (91%) were followed up and assessed at that age. The remaining children were either traced too late or their parents refused to participate in the study. This sample has been followed up at age 5 years (N= 991), age 7 years (7V=954), age 9 years (N=955), age 11 years (N= 925), age 13 years (N= 859), and most recently, age 15 years (Ar=976). The Dunedin sample is predominantly European and is underrepresentative of Polynesian children (about 3% in the sample compared with 12% for New Zealand). It is also slightly socioJournal of Learning Disabilities
economically advantaged when compared with the New Zealand population as a whole. At age 3 years, 22% of the sample came from an unskilled family background, 55% from a semi-skilled background, and 23% from a skilled background. The sample is representative of Dunedin children in terms of scores for tests of reading, spelling, mathematics, and listening comprehension, but is slightly underrepresentative of children with unmarried mothers. Members of the cohort were not chosen on the basis of any health, educational, or behavioral criteria, and are a representative sample of Dunedin children.
Reading Ability and IQ. At ages 7 and 9 years, reading ability was assessed with the Burt Word Reading Test-1974 Revision (Scottish Council for Research in Education, 1976). IQ scores were obtained at age 3 years with the Peabody Picture Vocabulary Test (Dunn, 1965), at age 5 years with the Stanford-Binet Intelligence Scale (Terman & Merrill, 1960), and at ages 7 and 9 years with the Wechsler Intelligence Scale for Children-Revised (WISC-R) (Wechsler, 1974). Additional information about the measures of reading and IQ can be found in Williams and Silva (1985).
Behavior Problems. In order to quantify the extent of behavioral problems shown by the children at school, the Family Adversity. Rutter (1978) sug- Child Scale B for completion by teachers gested that the number of risk factors, (Rutter et al., 1970) was administered as opposed to the nature of the risk fac- when the children were age 5, 7, 9, and tors, provides a more meaningful mea- 11 years. Teachers completed the Rutter sure of adversity in children's family questionnaire for children at age 5 years background. A cumulative risk index was during their first year at school. The used by Sameroff, Seifer, Barocos, Zax, Rutter questionnaire contains items reand Greenspan (1987) to examine the re- lating to hyperactive, antisocial, and lationship between family adversity and neurotic behaviors. IQ scores. An index of family adversity has also been used to examine the extent Data Analysis of problem behavior in the Dunedin sample at age 7 years (McGee, Silva, & IQ scores obtained at ages 3 and 5 years Williams, 1984). were standardized and averaged to obThe family adversity index used in the tain a more reliable and stable measure present study was derived from birth to of pre-school-age intellectual function3 years of age using a method similar to ing, which follows the procedure used by that described by Rutter (1978). The in- Share et al. (1989). A similar procedure dex was based on the following measures: was applied to the IQ scores obtained at father with semi-skilled or unskilled job ages 7 years (mean =106.9, SD= 14.5) at the time of the child's birth (based on and 9 years (mean= 104.4, SZ)=15.5), the SES Index developed by Elley & Irv- the reading scores obtained at ages 7 and ing, 1972) or solo mother at the time of 9 years, and the scores for the Rutter the child's birth; mother younger than 20 Child Scale B at ages 9 and 11 years. years old at the time of the birth of her There were 779 children (407 boys and first child; solo mother when study child 372 girls) for whom data were available was 3 years of age; family size of four for all these measures. An initial regresor more children; low maternal mental sion analysis was applied to the scores ability measured by the SRA Verbal scale obtained on the Child Scale B to deter(Thurstone & Thurstone, 1973) (score mine if there were significant effects for below the 10th percentile); mother's score the factors of family adversity (by age 3 on the Neuroticism scale of the Eysenck years) and pre-school-age IQ on behavior Personality Inventory (Eysenck & Ey- problems reported soon after school ensenck, 1964) above the 90th percentile. try. Further analyses were conducted to Each variable was scored as present (1) test for significant effects for the factors or absent (0), resulting in an index of of family adversity, reading ability, and scores with a possible range from 0 to 6, school-age IQ on changes in behavior indicating the degree of family adversity after school entry. Factors were entered by the child's third birthday. in the temporal order in which they could
Measures
Volume 23, Number 8, October 1990
be expected to influence children's development. The first analysis was performed on the behavior problem scores obtained during the first year at school (age 5 years). The second set of analyses was performed on the combined problem behavior scores obtained at ages 9 and 11 years. A third set of analyses was performed on these scores after controlling for problem behavior up to the children's first year at school. As multiple regression analyses were required to test each hypothesis, a level of significance of p< .01 was set for each analysis to minimize the Type I error rate.
RESULTS Table 1 gives the correlations between scores obtained on the measures of family adversity, pre-school-age IQ, reading ability, and school-age IQ measures. As the correlations were very similar for males and females, the data obtained for boys and girls were combined for the regression analyses described below. Results of the regression analyses (a-c) are shown in Table 2. A significant effect on problem behavior at age 5 was found for each of the factors entered in the order of family adversity and preschool-age IQ (p
of age, sex, and verbal IQ were controlled in the analysis of the data. Thus, the predictive significance of IQ for behavior problems may be a consequence of the confounding effects of reading disability, or vice versa. Furthermore, since levels of family Warren R. Stanton, Michael Feehan, Rob McGee, adversity are related to both IQ (Stanton, McGee, & Silva, 1989) and reading abiliand Phil A. Silva ty (McGee, Williams, & Silva, 1988), the reported relationships between low IQ scores, poor reading ability, and problem behavior could be accounted for by the Measures of early family adversity, pre-school-age IQ, school-age IQ, and reading ability were obtained from 779 Dunedin children. The data were used to examineeffects of family adversity. That is, after controlling for the effects of an adverse the role of reading ability in the relationship between intellectual performance and teacher-reported behavior problems. Results of regression analyses showed thatfamily background, there may be no evifamily adversity and pre-school-age IQ predicted problem behavior during the firstdence of the reported relationship beyear at school. However, reading scores accounted for a larger proportion of thetween reading, IQ, and problem behavior. Therefore, the aim of the present study variance in the later behavior problem scores than did school-age IQ scores, and was to examine the relative value of meawhen reading ability was entered in the regression equation before IQ, then reading but not IQ significantly predicted change in problem behavior during the primarysures of family adversity, reading, and IQ as predictors of problem behavior and school years. The results indicated that the association between IQ scores and probhence their relevance to models of problem behavior was mediated by reading ability and that a measure of school-age IQ lem behavior. has limited usefulness for models of primary school-age problem behavior.
R
eading ability and performance on IQ tests have been independently associated with the development of behavioral problems in childhood and early adolescence. Evidence to support a relationship between low IQ and behavioral problems was reported by Rutter, Tizard, and Whitmore (1970) in the Isle of Wight Study, and by McGee, Silva, and Williams (1983) in Dunedin, New Zealand. Hirschi and Hindelang (1977) reviewed the role of cognitive ability in the development of delinquency and concluded that lower intellectual performance is related to delinquent behavior through its effect on school performance. Similarly, others have reported a relationship between attention deficit disorder (ADD) or hyperactivity and IQ (August & Stewart, 1982; Schachar, Rutter, & Smith, 1981; Werry, Elkind, & Reeves, 1987). A link between reading difficulties and behavioral problems has been suggested by a number of researchers, including Carlson, Lahey, and Neeper (1986), McMichael (1979), Rutter et al. (1970), and Sturge (1982). Using the Rutter questionnaire, McGee et al. (1983) found that reading ability was significantly lower in groups of children with behavioral problems identified by the teacher alone, and by both parent and teacher, compared to the groups identified by parents only and 514
the remainder of the sample. Kavale, Alper, and Purcell (1981) suggested that reading disorder in children is strongly associated with teachers' judgments of behavior problems. However, reading ability and IQ have been shown to be significantly correlated. For example, Sattler (1982) reported a correlation of 0.6 for Wechsler Intelligence Scale for Children-Revised (WISCR) (Wechsler, 1974) Full Scale IQ scores and reading skills scores of the Wide Range Achievement Test (WRAT) (Jastak & Jastak, 1976). Share and Silva (1986) found that scores on the Burt Word Reading Test (Scottish Council for Research in Education, 1976) correlated with both the WISC-R Full Scale IQ scores (0.58) and the Performance IQ scores (0.42) administered at age 11 years. There is also evidence that changes in IQ scores can result from success in learning to read (Bishop & Butter worth, 1980; Share, McGee, & Silva, 1989). Few studies have examined the degree to which reading ability and IQ are related to problem behavior when the effect of the other is controlled in the analysis. Werry et al. (1987) reported a significant difference in reading scores between attention deficit disorder and conduct disorder groups and a control group, which persisted when the effects
METHOD Sample The sample consisted of children enrolled in the Dunedin Multidisciplinary Health and Development Study (DMHDS). They were part of a cohort born at the Queen Mary Maternity Hospital, Dunedin, between April 1, 1972, and March 31, 1973. A more detailed description of the sample is given by Silva (in press). In summary, the DMHDS is a longitudinal study of the health, development, and behavior of a cohort of New Zealand children. When the children were age 3 years, 1,139 were found to be living in Otago province. One thousand and thirty-seven (91%) were followed up and assessed at that age. The remaining children were either traced too late or their parents refused to participate in the study. This sample has been followed up at age 5 years (N= 991), age 7 years (7V=954), age 9 years (N=955), age 11 years (N= 925), age 13 years (N= 859), and most recently, age 15 years (Ar=976). The Dunedin sample is predominantly European and is underrepresentative of Polynesian children (about 3% in the sample compared with 12% for New Zealand). It is also slightly socioJournal of Learning Disabilities
economically advantaged when compared with the New Zealand population as a whole. At age 3 years, 22% of the sample came from an unskilled family background, 55% from a semi-skilled background, and 23% from a skilled background. The sample is representative of Dunedin children in terms of scores for tests of reading, spelling, mathematics, and listening comprehension, but is slightly underrepresentative of children with unmarried mothers. Members of the cohort were not chosen on the basis of any health, educational, or behavioral criteria, and are a representative sample of Dunedin children.
Reading Ability and IQ. At ages 7 and 9 years, reading ability was assessed with the Burt Word Reading Test-1974 Revision (Scottish Council for Research in Education, 1976). IQ scores were obtained at age 3 years with the Peabody Picture Vocabulary Test (Dunn, 1965), at age 5 years with the Stanford-Binet Intelligence Scale (Terman & Merrill, 1960), and at ages 7 and 9 years with the Wechsler Intelligence Scale for Children-Revised (WISC-R) (Wechsler, 1974). Additional information about the measures of reading and IQ can be found in Williams and Silva (1985).
Behavior Problems. In order to quantify the extent of behavioral problems shown by the children at school, the Family Adversity. Rutter (1978) sug- Child Scale B for completion by teachers gested that the number of risk factors, (Rutter et al., 1970) was administered as opposed to the nature of the risk fac- when the children were age 5, 7, 9, and tors, provides a more meaningful mea- 11 years. Teachers completed the Rutter sure of adversity in children's family questionnaire for children at age 5 years background. A cumulative risk index was during their first year at school. The used by Sameroff, Seifer, Barocos, Zax, Rutter questionnaire contains items reand Greenspan (1987) to examine the re- lating to hyperactive, antisocial, and lationship between family adversity and neurotic behaviors. IQ scores. An index of family adversity has also been used to examine the extent Data Analysis of problem behavior in the Dunedin sample at age 7 years (McGee, Silva, & IQ scores obtained at ages 3 and 5 years Williams, 1984). were standardized and averaged to obThe family adversity index used in the tain a more reliable and stable measure present study was derived from birth to of pre-school-age intellectual function3 years of age using a method similar to ing, which follows the procedure used by that described by Rutter (1978). The in- Share et al. (1989). A similar procedure dex was based on the following measures: was applied to the IQ scores obtained at father with semi-skilled or unskilled job ages 7 years (mean =106.9, SD= 14.5) at the time of the child's birth (based on and 9 years (mean= 104.4, SZ)=15.5), the SES Index developed by Elley & Irv- the reading scores obtained at ages 7 and ing, 1972) or solo mother at the time of 9 years, and the scores for the Rutter the child's birth; mother younger than 20 Child Scale B at ages 9 and 11 years. years old at the time of the birth of her There were 779 children (407 boys and first child; solo mother when study child 372 girls) for whom data were available was 3 years of age; family size of four for all these measures. An initial regresor more children; low maternal mental sion analysis was applied to the scores ability measured by the SRA Verbal scale obtained on the Child Scale B to deter(Thurstone & Thurstone, 1973) (score mine if there were significant effects for below the 10th percentile); mother's score the factors of family adversity (by age 3 on the Neuroticism scale of the Eysenck years) and pre-school-age IQ on behavior Personality Inventory (Eysenck & Ey- problems reported soon after school ensenck, 1964) above the 90th percentile. try. Further analyses were conducted to Each variable was scored as present (1) test for significant effects for the factors or absent (0), resulting in an index of of family adversity, reading ability, and scores with a possible range from 0 to 6, school-age IQ on changes in behavior indicating the degree of family adversity after school entry. Factors were entered by the child's third birthday. in the temporal order in which they could
Measures
Volume 23, Number 8, October 1990
be expected to influence children's development. The first analysis was performed on the behavior problem scores obtained during the first year at school (age 5 years). The second set of analyses was performed on the combined problem behavior scores obtained at ages 9 and 11 years. A third set of analyses was performed on these scores after controlling for problem behavior up to the children's first year at school. As multiple regression analyses were required to test each hypothesis, a level of significance of p< .01 was set for each analysis to minimize the Type I error rate.
RESULTS Table 1 gives the correlations between scores obtained on the measures of family adversity, pre-school-age IQ, reading ability, and school-age IQ measures. As the correlations were very similar for males and females, the data obtained for boys and girls were combined for the regression analyses described below. Results of the regression analyses (a-c) are shown in Table 2. A significant effect on problem behavior at age 5 was found for each of the factors entered in the order of family adversity and preschool-age IQ (p
