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Social-emotional behavior of preschool-age children with and without developmental delays
Pergamon
Rese~u-ch in Developmental Disabilities, Vol. 18, No. 6, pp. 393~I-05, 1997 Copyright © 1997 Elsevier Science Lid Printed in the USA. All rights reserved 0891-4222/97 $17.00 + ,00
PII S0891-4222(97)00018-8
Social-Emotional Behavior of Preschool-Age Children with and without Developmental Delays Kenneth W. Merrell The University of Iowa
Melissa Lea Holland Utah State University
Differences bz parent and teacher ratings of social-emotional behavior among young children with developmental delays and thase without sigre~ficant developmental probleres were examined. Participants included 19,~ preschool-age children ident(lied as having a developmental delay (DD group) and 198 preschool-age children without significant developmental probleres (Comparison group) who were reatched to the DD group by age and gemter, using a ramloreizea block procedure. Parent and teacher perceptions of social-emotional behavior of the participant~ were assessed using the Preschool and Kindergarten Behavior Scale (PKBS), a social skills and problem behavior rating scale for use with young children. PKBS scores were fimnd to classi[5' the partictpants into their re.wective groups with a substantial degree ~["accuracy. Statistically significant differences in social s~ills and problem behavior scores between the m,o groups were found, with the DD participants evidencing greater social skills deficits and problem behavior excesses than the Coreparison group. Individuals in the DD group were ~fbund m be fimr to fiw" times more likely m have significant social skills deficits and problem behavior excesses than individuals in the Coreparison group. The critk'al social-ereotional beh,~viors separating the two groups appeared to be social interaction and independence skills, and socially withdrawn and isolated behavior patterns. New validit3 et,ideFwefor the PKBS is discussed, as are Reprint requests should be sent to Kenneth W. Merrell. Division of Psychological and Quantitative Foundations, N334 Lindquist Center, The University of Iowa, lowa City, IA 52242-1569.
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K. W. Merrell a n d M. L. H o l l a n d
future needs pertaining to research and clinical practice in the area of socialemotional behavior ¢~young children with developmental delawv. © 1997Elsevier
Science Ltd
Developmental delay refers to a condition that indicates a significant delay in the process of a child's development (McLean, Smith, McCormick, Schakel, & McEvoy, 1991). This term includes children who perform below expected levels for their chronological age, regardless of the etiology of the delay (Brockman, Morgan, & Harmon, 1988; Copeland & Kimmel, 1989). In practice a "significant delay" in functioning is usually operationalized by a child performing at a specified level (e.g., 1 or 1.5 standard deviations) below the normative average for their age group on standardized norm-referenced tests in a particular area of development (e.g., social-emotional, communication, cognitive). The Individuals with Disabilities Education Act (IDEA) and the 1991 amendments (EL. 102-119) expanded services to young children with developmental delays through the addition of required services, by broadening the eligibility criteria, and by extending rights afforded school age children to infants, toddlers, and preschool-aged children. The category of preschool eligibility for developmental delay is intended to include children from 3 to 5 years of age. These children must have significant delays in one or more domains of cognitive, physical, communication, social/emotional, and adaptive development in order to qualify for special education and related services as a result of their delays (Bernheimer, Keogh, & Coots, 1993; Danaher, 1992). A confirmation of delayed development is obtained through a valid and reliable diagnostic assessment to confirm eligibility for services (Shonkoff & Meisels, 1991). The criteria for determining developmental delay according to a developmental assessment has varied among the several U.S. states, though usually it has been identifed in terms of standard deviations below the mean, percentage of delay in months or even a specified number of months delayed (McLean, et al., 1991). Young children with developmental delays have been found to be at risk for developing social, emotional, and behavioral problems. Social deficits are prevalent among children with developmental delays. In a study conducted by Kopp, Baker and Brown (1992), it was found that children with delays spent more time alone, and when they did play, they showed less social play. In this study, 88% of the nondelayed children were involved in social play, as opposed to only 67% of the children with delays. Only 53% of the children with developmental delays laughed and/or smiled to their peers in contrast to 93% of children without such delays (Kopp et al., 1992). Most preschool-aged children with developmental delays appear to have some difficulty in establishing more than simple social exchanges with their peers (Guralnick & Bricker, 1987). The social repertoire of young children with developmental delays has been found to be limited and fragmented, with unoccupied and solitary activities dominating their forms of social participation (Guralnick & Weinhouse, 1984). Results from a study by Guralnick and Groom
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(1985) indicate the existence of major deficits in peer-related social interactions for children with developmental delays and the absence of specific social behaviors highly associated with peer-related social competence. In contrast to the considerable research available on social deficits in children with developmental delays, there is a relative dearth in the literature in the area of behavioral and emotional problems of these children. Although various types of behavioral and emotional disorders have been reported in children with developmental delays (Kobe & Hammer, 1994), the research in this area is generally lacking. Prevalence data for symptoms of major depression among children with developmental delays has been found to typically vary between 10-20% (Kobe & Hammer, 1994). Behavior problems have also been found at a relatively high frequency in children with developmental delays (Bernheimer et al., 1993). However, beyond these general findings, relatively little is known. Unfortunately, it has been found that children with developmental delays do not "outgrow" their social deficits or behavioral problems. Social development in preschoolers often functions as a springboard to more advanced social activities later in children's development (Guralnick & Groom, 1985). Peer social relationships in preschool-aged children may promote or deter later child adjustment (Kopp et al., 1992). Thus, sociai~ deficits in young children can lead to poorer social development and adjustment later in childhood. Behavioral problems in young children with developmental delays have also been found to remain problematic in later childhood. For example, Bernheimer et al. (1993) found that at ages 6 and 7, over half of the children with delays continued to have multiple diagnoses, with increases in the use of labels such as AttentionDeficit Hyperactivity Disorder. Relatively recent findings indicate that the roots of serious behavioral problems, such as conduct disorders and related externalizing and antisocial behaviors, may be found with a relatively high degree of predictive validity in early childhood (Shaw, Keenan & Vondra, 1994). Behavior problems have been found to remain relatively stable in children with developmental delays, though the expression of the problems often changes as children grow older, moving from immaturity to problems associated with behavioral disturbance (Bernheimer et al., 1993). Until recently, far more emphasis has been placed on the research of cognitive difficulties of children with developmental delays than on their socialemotional functioning (Kopp et al., 1992). In light of the trend toward early intervention, additional research is needed that focuses on early detection and assessment of social-emotional problem behavior in young children, particularly those who are at-risk for developing serious problems later in life (Kobe & Hammer, 1994). Assessment of behavioral deficits and excesses in children with developmental delays is essential for effective intervention (Guralnick & Bricker, 1987). Although there is a strong need for broad-based behavioral assessment of young children, relatively few instruments and methods have been developed specifically for use with the early childhood/preschool population. Of the instruments
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K. W. Merrell and M. L. Holland
Table 1 Breakdown of Study Sample by Age and Gender
Age Sex
3
4
5
Total
Male Female Total
56 40 96
88 44 132
100 70 170
244 154 398
that are currently available for use with this age group, many cannot demonstrate adequate reliability or test validity and have not undergone the evaluation procedures to be considered psychometrically ,;ound (McLean et al., 1991). Additionally, many of the existing instruments have inadequate standardization samples (Merrell, 1994a). Although there are a few existing behavior rating scales developed for use with the early childhood population that have utilized sophisticated development procedures and have adequate psychometric properties, the research and clinical needs surrounding early childhood behavioral assessment are varied enough that these instruments cannot possibly fulfill .all assessment purposes (Merrell, 1995a). Thus, there is a strong need for the development of new and technically adequate instruments for the assessment of the social and emotional behavior of young children (Bracken, Keith, & Walker, 1994), particularly children with developmental delays or other high-risk conditions. The purpose of this study was two-fold: to further the knowledge about social-emotional behavior of children with developmental delays, and to provide validity evidence and research information on a new and potentially useful behavioral measure for use with the early childhood/preschool population, namely the Preschool and Kindergarten Behavior Scales (PKBS; Merrell, 1994b). The specific focus of the research presented in this article is to provide evidence of the ability of the PKBS to accurately distinguish social skills and problem behavior patterns between children with developmental delays and children without such delays.
METHOD
Participants and Procedure
Participants included 398 preschool-age children (ages 3-5) who were part of the PKBS national normative sample. These children all attended public or private preschools or Head Start programs, and they were all rated by either a parent or teacher using the PKBS. A gender by age breakdown of this sample is presented in Table t. As the data in this table indicate, 61.3% of the participating children were boys, whereas 38.7% were. girls. This gender breakdown is similar to the gender breakdown of U.S. students with disabilities who receive special
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education services, which is approximately 68% male (U.S. Department of Education, Office of Special Education Programs, t 993). Based on demographic information supplied by the teacher or parent completing the rating, the racial/ ethnic breakdown of the sample was as follows: 72.6% Caucasian, 16.3% African American, 6.3% Hispanic, .3% Asian American, .5% Native American, and the race/ethnicity of 4% of the sample was described as either "unknown" or "other." A selection procedure was used to divide the subjects into two groups and to ensure that these groups were comparable on important demographic variables. The first group consisted of 199 children (122 boys and 77 girls) who had been formally identified as developmentally delayed prior to the PKBS rating being completed. This group, referred to hereafter as the Developmentally Delayed (DD) group, included all of the children in the PKBS national normative sample who had been formally identified as havin~ a developmental delay. Because of the method of demographic data collection ased, no details were known regarding the specific area or areas of delay, and because these children were from several states and varying sites, the details regarding how they were identified as developmentally delayed are unknown. However, for purposes of this study, it may be assumed that each child in the DE) group had been formally identified as having a developmental delay based oa the standard criteria of having a significant delay in one or more areas of development (e.g., cognitive, motor, language/speech, social/emotional, self-help/adaptive behavior). The second group (the Comparison group) included 199 children who were not identified as having a developmental delay (or any other disability). These children were selected from the PKBS national normative group using a randomized block procedure (Campbell & Stanley, t968) to match the DD group based on the demographic variables of age and gender. Thus, the DD group and the Comparison group each contained the same age breakdown and gender composition. Instrumentation
The PKBS is a 76-item behavior rating scale designed to measure social skills and social-emotional problem behaviors of children ages 3-6. This instrument may be completed by parents, teachers, daycare providers, or others who are familiar with a given child's behavior. It was designed specifically to represent routine or typical social skills and social-emotional problems specific to preschool and kindergarten-aged children, and to be a "user friendly" easy-to-use assessment instrument. The PKBS was developed with a national normative sample of 2,855 children from 16 different states representing each of the four U.S. geographical region from the U.S. Bureau of the Census categories. The PKBS normative sample approximated the general U.S. population in terms of gender, ethnicity, and socioeconomic status. For example, 51% of the standardization sample were male and 49% were female; 80% of the sample were Caucasian and 20% were
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K. W. MerrelI and tl/1. L. Holland
members of racial or ethnic minority groups (12.1% African American, 5.2% Hispanic, 1.5% Asian or Pacific Islander, .01% American Indian, and 1.2% "other"). Based on parent occupation of the subjects (an index of socioeconomic status), similarity was found in occupational categories of the normative population when compared with the most recent occupational breakdown statistics from the U.S. Bureau of the Census. Of the 2,855 child ratings that comprised the PKBS normative sample, 51.5% of the ratings were completed by preschool teachers, kindergarten teachers, or other school personnel, whereas 48.5% were completed by parents or other caregivers (i.e., grandparents or legal guardians). Rather than being a downward extension of a rating scale designed for use with older children or adolescents, the PKBS and its items were designed specifically with the unique social-emotional aspects of the early childhood/ preschool developmental period in mind, employing systematic item development and content validation procedures. In other words, the initial item pool for the PKBS was developed following a comprehensive and systematic review of research and clinical literature describing social ~skills and behavioral-emotional problems of young children and how these problems are specifically manifested in the preschool- to kindergarten-aged range. PKBS items comprise two separate scales, each designed to measure a different domain - - a 34-item Social Skills scale, and a 42-item Problem Behavior scale. Each of these two scales includes an empirically derived subscale structure. The Social Skills scale includes the following subscales: Social Cooperation (12 items describing cooperative and self-restraint behaviors), Social Interaction (11 items reflecting social initiation behaviors), and Social Independence (11 items reflective of behaviors that are important in gaining independence within the peer group). The Problem Behavior scale includes two broad-band subscales, Internalizing Problems and Externalizing Problems. Consistent with the theoretical and empirical breakdown of the internalizing/externalizing problem dichotomy (see Cicchetti & Toth, 1991), the latter broad-band scale includes 27 items describing undercontrolled behavioral problems, such as overactivity, aggression, coercion, and antisocial behaviors, while the former broad-band scale includes 15 items describing overcontrolled behavioral/emotional problems, such as social withdrawal, anxiety, somatic complaints, and behaviors consistent with depressive symptomatology. The Externalizing Problems broad-band scale includes three narrow-band scales (Self-Centered~Explosive, Attention Problems~Overactive, and AntisocialZ4ggressive), while the Internalizing Problems broad-band scale includes two narrow-band scales (Social Withdrawal and Anxiety~Somatic Problems). The PKBS scale configuration with sample items is presented in Table 2. Research findings presented in the PKBS test manual and in other published sources provide evidence for adequate to excellent psychometric properties (reliability and validity). Internal consistency reliability estimates for the Social Skills and Problem Behavior total scores are .96 and .97, respectively. Test-
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Table 2 Scale Structure and Sample Items from the Preschool and Kindergarten Behavior Scales
Scale Numbers and Names
Sample Items
Scale A, Social Skills
A1 Social Cooperation ( 12 items) A2 Social Interaction (11 items) A3 Social Independence ( 11 items)
Shares toys and other belongings;follows rules Invites other children to play; participates in classroom or family discussions Works or plays independently;attempts new tasks before asking for help
Scale B, Problem Behavior
B1 Self-Centered/Explosive (11 items) B2 AttentionProblems/Overactive (8 items) B3 Antisocial/Aggressive (8 items) B4 Social Withdrawal (7 items) B5 Anxiety/SomaticProblems (8 items)
Has temper outbursts or tantrums; wants all the attention Acts impulsixelywithout thinking; makes noises that annoy others Is physicallyaggressive; bullies or intimidatesother children Does not respond to affection from others; avoids playing with other children Becomes sick when upset or afraid; clings to parent or caregiver
Note. Subscales BI, B2, and B3 comprise the ExternalizingProblems broad-bandscale; subscales B4 and B5 comprise the InternalizingProblems broad-bandscale.
retest reliability estimates at 3-month interw~ls were respectively found to be .69 and .78. Child ratings by preschool teachers and teacher aides for the respective total scores have been shown to correlate ;at .48 and .59. Content validity has been demonstrated through documentation of the item development procedures and through showing moderate to high correlations between individual items and total scores. Construct validity has been demonstrated through analysis of intrascale relationships, factor analytic findings with structural equation modeling (Merrell, 1996), and documentation of sensitivity to various group differences (Jentzsch & Merrell, 1996; Merrell, 1995a). Convergent and discriminant construct validity has been demonstrated through examining relationships with four other established preschool behavior rating scales, namely, the Conners Teacher Rating Scale, the Matson Evaluation of Social Skills with Young Children, the School Social Behavior Scales, and the Social Skills Rating System (Merrell, 1995b).
RESULTS The overall separation of the two groups and classification properties of the PKBS were tested using a discriminant function analysis, a multivariate procedure used to determine the accuracy of group classification based on the statistical properties of test scores. In other words, tile question answered in the
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Table 3 Subscales of the Preschool and Kindergarten Behavior Scales, with Pooled-Within-Groups Correlation Coefficients from the Discriminant Function Analysis Structure Matrix, Listed in Order of Descending Power
Scale A2 Social Interaction B4 Social Withdrawal A3 Social Independence B2 Attention Problems/Overactive AI Social Cooperation B5 Anxiety/Somatic Problems B 1 Self-Centered/Explosive B3 Antisocial/Aggressive
Correlation .78 .74 .70 .54 .51 .48 .47 .21
discriminant function is essentially "how well do the behavior rating scores from the PKBS separate and classify the DD and comparison groups?" In this analysis group membership (DD vs. Comparison) served as the grouping variable, and the eight PKBS subscale ,scores served as classification variables. The resulting discriminant function was significant, indicating that the combined PKBS scores separated and classified the two groups in a statistically significant manner: Wilks' Lambda F = .75, X2(8) = 110.92, p < .0001. The classification results table from the discriminant analysis indicated that overall, 71.36% of the children were classified correctly into their respective groups based solely on the statistical properties of the PKBS scores, including 67.3% of the DD group, and 75.4% of the Comparison group. In discriminant analysis, a structure matrix is produced, showing the relationships between the discriminating variables (in this case, the PKBS subscale scores) and the separation or classification of groups (in this case, the DD and Comparison groups). The resulting pooledwithin-groups correlations are presented in Table 3. The correlations range fi'om .21 to .78. Three PKBS subscales (A2 Social Interaction, B4 Social Withdrawal, and A3 Social Independence) were correlated substantially higher than the other subscales with the separation of the two groups, with correlations in the .70s. Following the discriminant analysis, mean PKBS scores of the two groups were compared and contrasted. A one-way analysis of variance (ANOVA) was conducted, using group membership as the independent variable and the PKBS scores as dependent variables. Descriptive statistics of the PKBS scores for the two groups are presented in Table 4, along with the F statistics and probability levels from the ANOVA. As these data indicate, all of the PKBS Social Skills scores of the DD group were significantly lower (p < .0001) than those of the comparison group, indicating that they were rated by parents and teachers as having significantly lower levels of social skills in comparison with non-DD peers. Additionally, all of the PKBS Problem Behavior scores of the DD group were significantly higher (p < .05 to p < .0001) than those of the Comparison
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Table 4 PKBS Scores of Developmentally Delayed and Matched Comparison Children: Descriptive Statistics, ANOVA Resulls, and Effect Size Estimates DD
Scale A: Social Skills Al Social Cooperation A2 Social Interaction A3 Social Independence AT Total Social Skills Scale B: Problem Behavior B 1 Self-Centered/Explosive B2 Attention Problems/Overactive B3 Antisocial/Aggressive Externalizing Total B4 Social Withdrawal B5 Anxiety/Somatic Problems Internalizing Total Total Problem Behavior
Comparison
M
SD
M
SD
F (1,396)
ES (Magnitude)
25.42 19.16 23.74 68.32
6.98 7.02 6.04 18.23
29.23 25.28 27.91 82.42
6.02 5.49 4.32 13.79
33.89** 78.79** 62.80** 75.68**
.59(medium) .90 (large) .81 (large) .88 (large)
14.35 12.33 6.78 33.45 8.47 8.67 17.14 50.59
8.43 6.21 5.86 18.93 4.42 5.11 8.5t 24.88
10.16 8.73 5.52 24.41 4.95 6.12 l 1.07 35.48
7.12 5.41 4.79 16.18 3.82 4.11 7.17 21.80
28.62** 37.93** 5.48* 26.21"* 71.89"* 30.15"* 59.12" 41.49'*
.54(medium) .62(medium) .24 (small) .51(medium) .85 (large) .55(medium) .77(medium) .63(medium)
*p < .05. **p < .0001.
group, indicating that these children were rated by parents and teachers as having significantly higher levels of both internalizing and externalizing problem behaviors in comparison with non-DD peers. The statistical power or practical significance of these differences in PKBS scores between the DD and Comparison groups was tested by computing effect size (ES) estimates, using Cohen's d method (Cohen, 1988): the mean scores of the Comparison group were subtracted from the mean scores of the DD group, and the resulting difference was divided by the harmonic standard deviation of the two groups. The resulting ES estimate (d) is interpreted as an index of how much overlap exists in the distribution of scores of each group. In other words, an effect size estimate of .50 would indicate that the mean score of one group was approximately .5 standard deviation higher than the mean score of the other group. The ES estimates are also presented in Table 4, along with conventional magnitude indicators for practical interpretation suggested by Cohen (1988), wherein small effects range from .20 to .49, medium effects range from .50 to .79, and large effects are those at or above .80. As these data indicate, all of the ES estimates for the PKBS score differences between the DD and Comparison groups had practical or clinical importance, and all but one were either at the medium or large magnitude level. The PKBS subscales with "large" effect sizes were the same ones that correlated highly with the separation of the two groups in the discriminant analysis: A2 Social Interaction (ES = .90), B4 Social Withdrawal (ES--.85), and A3 Social Independence (ES = .81).
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Although comparisons of mean scores between groups provide valuable information regarding the overall trend and distribution of scores, they are not especially useful in describing the social-behavioral characteristics of individuals within groups. Therefore, the frequency distributions of each group were examined to determined what percentage within each group had significant social skills deficits and problem behavior excesses. The total Social Skills (A Total) and Problem Behavior (B Total) scores of each group were examined, using a clinical significance criteria of 1.5 standard deviations below the normative mean for social skills and 1.5 standard deviations above the normative mean for problem behavior. The 1.5 standard deviation criteria was used as a standard because it is often used as an efl'ective screening criterion in educational and clinical settings (Merre]l, 1994a). Using these criteria, 26.6% of the DD group but only 6% of the Comparison were identified as having significant social skills deficits, whereas 22% of the DD group but only 6% of the Comparison group were identified as having significant problem behavior excesses.
DISCUSSION The results of this study provide compelling evidence that as a group, preschoolaged children identified as having developmental delays were rated by teachers and parents as having significantly lower levels of social skills and significantly higher levels of problem behavior than children without identified developmental problems. These differences in social, emotional, and behavioral problems were both statistically significant and of practical clinical importance, as indicated by results of the inferential statistical tests and by the effect size estimates. It is interesting to consider that the PKBS scores were quite effective in classifying the DD and Comparison group participants into their respective groups, with approximately three fourths of all participants being classified correctly into their group based solely on the statistical properties of the PKBS scores. Had all of the participants in the study been classified as developmentally delayed because of problems in social-behavioral functioning, one might have anticipated such a result. However, we can only presume that the DD group was comprised of children who were classified as DD due to delayed functioning in a wide variety of areas, not just social-behavioral functioning. Thus, these results provide additional strong suppolt to previous research, which suggests that, as a group, children with developmental delays are at much higher risk than typically developing children for exhibiting deficits in social skills and excesses in a variety of behavioral and emotional problems. This risk factor is borne out by the fact that our analysis of frequency distributions indicated that being classified as having a developmental delay makes it f o u r to five times as likely that a child will have a clinically significant social skills deficit or behavioralemotional problem excess than a child who has not been identified as having a developmental delay.
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The placement or locus of the most substantial social-behavioral differences between the two groups is also intriguing. The discriminant analysis procedure and effect size calculations of PKBS scores between the two groups both indicated that three PKBS subscales stood out as showing the most powerful or strongest differences in social-emotional behavior between the two groups: A2 Social Interaction, B4 Social Withdrawal, and A3 Social Independence. The nature of the items in these three subscales share certain key characteristics and provide some additional insights into the critical differences between the two groups. Essentially, these three PKBS subscales contain items that measure a child's ability to interact successfully and independently with other children and adults. It appears that in contrast to the Comparison group, the DD group participants were rated as being particularly deficient in initiating social interactions and in working or playing independently, as well as showing excesses in avoidant and socially withdrawn behavior. Of course, it is important to remember that the PKBS scores of the DD group were significantly more problematic than those of the Comparison group in all areas, but these three related subscales represent by far the strongest differences. These results provide additional evidence for the validity of the PKBS because of the sensitivity to group differences in social-emotional behavior that was evidenced. Considered in conjunction with the other validity evidence referred to in the Method section of this paper, there appears to be mounting evidence that the PKBS is a valid and technically sound behavior rating scale for research and clinical assessment with young children. The PKBS offers the advantages of being practical, easy to use, and being targeted at the most common types of behavioral, social, and emotional problems exhibited by young children in a variety of settings. In addition to the main findings and positive aspects of this investigation, some potential limitations should also be considered. One limitation of this study was that only one method of assessment (behavior rating scales) was utilized. Because each method of assessment contains specific types of limitations and sources of error variance, it is more desirable to conduct descriptive and causal-comparative studies, such as this one using multiple types of assessment data. Related to this issue is the fact that behavior rating scales measure raters' perceptions of behavior rather than actual child behavior. One can presume that the rated perceptions of child behavior using the PKBS in this study are consistent with actual child behavior, but in the absence of supporting behavioral observation data, such a conclusion must be viewed as tentative. Use of a multimethod, multisource, multisetting assessment design (Merrell, 1994a) is the preferred optimum approach for obtaining broad-based and aggregated assessment information, and would enhance the confidence with which such results may be interpreted. Another limitation of this research is that little information regarding the subjects other than their PKBS scores and basic demographic information was available. Ideally, it would be best to know more about why the participants in
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the DD group were classified as having a developmental delay. With this data set, we can only presume that the DD participants were a heterogenous group of children who were identified and class:ified using a wide variety of criteria for a wide variety of developmental problems. The present data set does not allow for analyses and inferences regarding the potential confound of mental age, and does not shed any light on whether the PKBS is equally valid for assessing a wide range versus a restricted range of developmental delays. Additionally, it is not known how representative each of the two study groups were in relation to the larger groups (Dr) and normal children), which they were purported to sample and represent on several important variables. Additional research would help clarify some of these issues. However, it is important to recognize that the randomized block selection procedure used to select study participants from the larger data set should theoretically ensure or at least increase the probability of representativeness of the study groups (Campbell & Stanley, 19681. Finally, it is important to consider some future directions in research and clinical practice with young children who have developmental delays. Understanding the social-emotional behavior and related characteristics of these children is a very important endeavor, as is the development and refinement of technically adequate and clinically use,ful assessment instruments. However, linking knowledge and practice in these areas to effective prevention and intervention efforts is perhaps the most important challenge being faced within the field. Future research efforts that build upon tlhe present investigation in this manner will allow for increasingly important developments and refinements in effective service delivery to young children with developmental delays, disabilities, and related problems. REFERENCES Bernheimer, L. P., Keogh, B. K., & Coots, J. J. (1993). From research to practice: Support for developmental delay as a preschool category of exceptionality. Journal of Early Intervention, 17, 97-1 (16. Bracken, B. A., Keith, L. K., & Walker, K. C. (19941. Assessment of preschool behavior and socialemotional functioning: A review of thirteen third-party instruments. Assessment in Rehabilitation and Exceptionality, 1, 331-346. Brockman, L. M., Morgan, G. A., & Harmon, R. J. (1988). Mastery motivation and developmental delay. In T. D. Wachs & R. Sheenan (Eds.), Asse.~smet~'t qfyoung developmentally disabled children (pp. 267-284). New York: Plenum Press. Campbell, D. T., & Stanley, J. C. (1968). Erper.;menml and quasi-experimental mseorch design. Chicago: Rand-McNalty. Cicchetti, D., & Toth, S. L. (1991). A developmental perspeclive on internalizing and externalizing disorders. In D. Cicchetti & S. L. Toth (Eds.), lnternali=mg and externalizing expressions of dysfunction (pp. 1-19). Hillsdale, NJ: Lawrence ]Erlbaum Associates. Cohen, J. (19881. Statistical power atlalvsis ./~r the behavioral sciences (2nd. ed.). Hillsdale, NJ: Lawrence Erlbaum Associates. Copeland, M. E., & Kimmel, J. R. (19891. Evaluati~m and management q/' #zfants and young children with developmental disabilities. Baltimore, MD: Paul H. Brookes Publishing Co.
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Danaher, J. (1992). Preschool special education eligibilio" classifications and criteria. Chapel Hill, NC: National Early Childhood Technical Assistance System (NEC*TAS). (Eric Document Reproduction Service No. ED 351 847). Guralnick, M. J., & Bricker, D. (1987). The effectiveness of early intervention for children with cognitive and general developmental delays. In M. J. Guralnick & E C. Bennett (Eds.), The effectiveness ~?]' early intervention for at-risk and hamtieapped children (pp. 115-173). Orlando, FL: Academic Press, Inc. Guralnick, M. J., & Groom, J. M. (1985). Correlates of :3eer-related social competence of developmentally delayed preschool children. American Journal (!f Mental Deficiency, 90, 140-150. Guralnick, M. J., & Weinhouse, E. (1984). Peer-related social interactions of developmentally delayed young children: Development and characteristics. Developmental Psychology, 20, 815-827. Jentzsch, C. E., & MerrelL K. W. (1996). An investigation of the construct validity of the Preschool and Kindergarten Behavior Scales. Diagnostique, 21, 1-15. Kobe, E H., & Hammer, D. (1994). Parenting stress and. depression in children with mental retardation and developmental disabilities. Research in Developmental Disabilities, 15, 209-221. Kopp, C. B., Baker, B. L., & Brown, K. W. (1992). Social skills and their correlates: Preschoolers with developmental delays. American Journal on Mental Retardation, 96, 357-366. McLean, M., Smith, B. J., McCormick, K., Schakel, J., & McEvoy, M. (1991). Developmental delay: Establishing parameters fi~r a preschool eategoo' of exceptional#v. Reston, VA: Council for Exceptional Children, Division for Early Childhood. (Eric Document Reproduction Service N. ED 343 37l). Men-ell, K. W. (1994a). Assessment of behavioral, sociai, and emotional problems: Direct and objective methods for use with children and adolescents. New York: Addison Wesley/Longman. Merrell, K. W. (1994b). The Preschool and Kindergarten Behavior Scales. Austin, TX: PRO-ED. Merrell, K. W. (1995a). An investigation of the relationship between social skills and internalizing problems in early childhood: Construct validity of the Preschool and Kindergarten Behavior Scales. Journal of P.~'choeducational Assessment, 13, 230-240. Merrell, K. W. (1995b). Relationships among early childhood behavior rating scales: Convergent and discfiminant construct validity of the Preschool and Kindergarten Behavior Scales. Early Education and Development, 6, 253-264. Merrell, K. W. (1996). Assessment of social skills and behavior problems in early childhood: The Preschool and Kindergarten Behavior Scales. Journal of Early lnteta,'ention, 20, 132-145. Shaw, D. S., Keenan, K., & Vondra, J. 1. (1994). Developmental precu~ors of externalizing behavior: Ages 1 to 3. Developmental Psychology, 30, 355-364. Shonkoff, J. R, & Meisels, S. J. (1991). Defining eligibility for ser',,ices under PL 99-457. Journal ~[ Early lnteta,ention, 15, 21-25. U.S. Department of Education, Office of Special Education Programs. (1993). First-fifteenth annual reports to Congress on the implementation of the Individuals with Disabilities Education Act. Washington, DIS: Author.
Rese~u-ch in Developmental Disabilities, Vol. 18, No. 6, pp. 393~I-05, 1997 Copyright © 1997 Elsevier Science Lid Printed in the USA. All rights reserved 0891-4222/97 $17.00 + ,00
PII S0891-4222(97)00018-8
Social-Emotional Behavior of Preschool-Age Children with and without Developmental Delays Kenneth W. Merrell The University of Iowa
Melissa Lea Holland Utah State University
Differences bz parent and teacher ratings of social-emotional behavior among young children with developmental delays and thase without sigre~ficant developmental probleres were examined. Participants included 19,~ preschool-age children ident(lied as having a developmental delay (DD group) and 198 preschool-age children without significant developmental probleres (Comparison group) who were reatched to the DD group by age and gemter, using a ramloreizea block procedure. Parent and teacher perceptions of social-emotional behavior of the participant~ were assessed using the Preschool and Kindergarten Behavior Scale (PKBS), a social skills and problem behavior rating scale for use with young children. PKBS scores were fimnd to classi[5' the partictpants into their re.wective groups with a substantial degree ~["accuracy. Statistically significant differences in social s~ills and problem behavior scores between the m,o groups were found, with the DD participants evidencing greater social skills deficits and problem behavior excesses than the Coreparison group. Individuals in the DD group were ~fbund m be fimr to fiw" times more likely m have significant social skills deficits and problem behavior excesses than individuals in the Coreparison group. The critk'al social-ereotional beh,~viors separating the two groups appeared to be social interaction and independence skills, and socially withdrawn and isolated behavior patterns. New validit3 et,ideFwefor the PKBS is discussed, as are Reprint requests should be sent to Kenneth W. Merrell. Division of Psychological and Quantitative Foundations, N334 Lindquist Center, The University of Iowa, lowa City, IA 52242-1569.
393
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K. W. Merrell a n d M. L. H o l l a n d
future needs pertaining to research and clinical practice in the area of socialemotional behavior ¢~young children with developmental delawv. © 1997Elsevier
Science Ltd
Developmental delay refers to a condition that indicates a significant delay in the process of a child's development (McLean, Smith, McCormick, Schakel, & McEvoy, 1991). This term includes children who perform below expected levels for their chronological age, regardless of the etiology of the delay (Brockman, Morgan, & Harmon, 1988; Copeland & Kimmel, 1989). In practice a "significant delay" in functioning is usually operationalized by a child performing at a specified level (e.g., 1 or 1.5 standard deviations) below the normative average for their age group on standardized norm-referenced tests in a particular area of development (e.g., social-emotional, communication, cognitive). The Individuals with Disabilities Education Act (IDEA) and the 1991 amendments (EL. 102-119) expanded services to young children with developmental delays through the addition of required services, by broadening the eligibility criteria, and by extending rights afforded school age children to infants, toddlers, and preschool-aged children. The category of preschool eligibility for developmental delay is intended to include children from 3 to 5 years of age. These children must have significant delays in one or more domains of cognitive, physical, communication, social/emotional, and adaptive development in order to qualify for special education and related services as a result of their delays (Bernheimer, Keogh, & Coots, 1993; Danaher, 1992). A confirmation of delayed development is obtained through a valid and reliable diagnostic assessment to confirm eligibility for services (Shonkoff & Meisels, 1991). The criteria for determining developmental delay according to a developmental assessment has varied among the several U.S. states, though usually it has been identifed in terms of standard deviations below the mean, percentage of delay in months or even a specified number of months delayed (McLean, et al., 1991). Young children with developmental delays have been found to be at risk for developing social, emotional, and behavioral problems. Social deficits are prevalent among children with developmental delays. In a study conducted by Kopp, Baker and Brown (1992), it was found that children with delays spent more time alone, and when they did play, they showed less social play. In this study, 88% of the nondelayed children were involved in social play, as opposed to only 67% of the children with delays. Only 53% of the children with developmental delays laughed and/or smiled to their peers in contrast to 93% of children without such delays (Kopp et al., 1992). Most preschool-aged children with developmental delays appear to have some difficulty in establishing more than simple social exchanges with their peers (Guralnick & Bricker, 1987). The social repertoire of young children with developmental delays has been found to be limited and fragmented, with unoccupied and solitary activities dominating their forms of social participation (Guralnick & Weinhouse, 1984). Results from a study by Guralnick and Groom
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(1985) indicate the existence of major deficits in peer-related social interactions for children with developmental delays and the absence of specific social behaviors highly associated with peer-related social competence. In contrast to the considerable research available on social deficits in children with developmental delays, there is a relative dearth in the literature in the area of behavioral and emotional problems of these children. Although various types of behavioral and emotional disorders have been reported in children with developmental delays (Kobe & Hammer, 1994), the research in this area is generally lacking. Prevalence data for symptoms of major depression among children with developmental delays has been found to typically vary between 10-20% (Kobe & Hammer, 1994). Behavior problems have also been found at a relatively high frequency in children with developmental delays (Bernheimer et al., 1993). However, beyond these general findings, relatively little is known. Unfortunately, it has been found that children with developmental delays do not "outgrow" their social deficits or behavioral problems. Social development in preschoolers often functions as a springboard to more advanced social activities later in children's development (Guralnick & Groom, 1985). Peer social relationships in preschool-aged children may promote or deter later child adjustment (Kopp et al., 1992). Thus, sociai~ deficits in young children can lead to poorer social development and adjustment later in childhood. Behavioral problems in young children with developmental delays have also been found to remain problematic in later childhood. For example, Bernheimer et al. (1993) found that at ages 6 and 7, over half of the children with delays continued to have multiple diagnoses, with increases in the use of labels such as AttentionDeficit Hyperactivity Disorder. Relatively recent findings indicate that the roots of serious behavioral problems, such as conduct disorders and related externalizing and antisocial behaviors, may be found with a relatively high degree of predictive validity in early childhood (Shaw, Keenan & Vondra, 1994). Behavior problems have been found to remain relatively stable in children with developmental delays, though the expression of the problems often changes as children grow older, moving from immaturity to problems associated with behavioral disturbance (Bernheimer et al., 1993). Until recently, far more emphasis has been placed on the research of cognitive difficulties of children with developmental delays than on their socialemotional functioning (Kopp et al., 1992). In light of the trend toward early intervention, additional research is needed that focuses on early detection and assessment of social-emotional problem behavior in young children, particularly those who are at-risk for developing serious problems later in life (Kobe & Hammer, 1994). Assessment of behavioral deficits and excesses in children with developmental delays is essential for effective intervention (Guralnick & Bricker, 1987). Although there is a strong need for broad-based behavioral assessment of young children, relatively few instruments and methods have been developed specifically for use with the early childhood/preschool population. Of the instruments
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K. W. Merrell and M. L. Holland
Table 1 Breakdown of Study Sample by Age and Gender
Age Sex
3
4
5
Total
Male Female Total
56 40 96
88 44 132
100 70 170
244 154 398
that are currently available for use with this age group, many cannot demonstrate adequate reliability or test validity and have not undergone the evaluation procedures to be considered psychometrically ,;ound (McLean et al., 1991). Additionally, many of the existing instruments have inadequate standardization samples (Merrell, 1994a). Although there are a few existing behavior rating scales developed for use with the early childhood population that have utilized sophisticated development procedures and have adequate psychometric properties, the research and clinical needs surrounding early childhood behavioral assessment are varied enough that these instruments cannot possibly fulfill .all assessment purposes (Merrell, 1995a). Thus, there is a strong need for the development of new and technically adequate instruments for the assessment of the social and emotional behavior of young children (Bracken, Keith, & Walker, 1994), particularly children with developmental delays or other high-risk conditions. The purpose of this study was two-fold: to further the knowledge about social-emotional behavior of children with developmental delays, and to provide validity evidence and research information on a new and potentially useful behavioral measure for use with the early childhood/preschool population, namely the Preschool and Kindergarten Behavior Scales (PKBS; Merrell, 1994b). The specific focus of the research presented in this article is to provide evidence of the ability of the PKBS to accurately distinguish social skills and problem behavior patterns between children with developmental delays and children without such delays.
METHOD
Participants and Procedure
Participants included 398 preschool-age children (ages 3-5) who were part of the PKBS national normative sample. These children all attended public or private preschools or Head Start programs, and they were all rated by either a parent or teacher using the PKBS. A gender by age breakdown of this sample is presented in Table t. As the data in this table indicate, 61.3% of the participating children were boys, whereas 38.7% were. girls. This gender breakdown is similar to the gender breakdown of U.S. students with disabilities who receive special
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397
education services, which is approximately 68% male (U.S. Department of Education, Office of Special Education Programs, t 993). Based on demographic information supplied by the teacher or parent completing the rating, the racial/ ethnic breakdown of the sample was as follows: 72.6% Caucasian, 16.3% African American, 6.3% Hispanic, .3% Asian American, .5% Native American, and the race/ethnicity of 4% of the sample was described as either "unknown" or "other." A selection procedure was used to divide the subjects into two groups and to ensure that these groups were comparable on important demographic variables. The first group consisted of 199 children (122 boys and 77 girls) who had been formally identified as developmentally delayed prior to the PKBS rating being completed. This group, referred to hereafter as the Developmentally Delayed (DD) group, included all of the children in the PKBS national normative sample who had been formally identified as havin~ a developmental delay. Because of the method of demographic data collection ased, no details were known regarding the specific area or areas of delay, and because these children were from several states and varying sites, the details regarding how they were identified as developmentally delayed are unknown. However, for purposes of this study, it may be assumed that each child in the DE) group had been formally identified as having a developmental delay based oa the standard criteria of having a significant delay in one or more areas of development (e.g., cognitive, motor, language/speech, social/emotional, self-help/adaptive behavior). The second group (the Comparison group) included 199 children who were not identified as having a developmental delay (or any other disability). These children were selected from the PKBS national normative group using a randomized block procedure (Campbell & Stanley, t968) to match the DD group based on the demographic variables of age and gender. Thus, the DD group and the Comparison group each contained the same age breakdown and gender composition. Instrumentation
The PKBS is a 76-item behavior rating scale designed to measure social skills and social-emotional problem behaviors of children ages 3-6. This instrument may be completed by parents, teachers, daycare providers, or others who are familiar with a given child's behavior. It was designed specifically to represent routine or typical social skills and social-emotional problems specific to preschool and kindergarten-aged children, and to be a "user friendly" easy-to-use assessment instrument. The PKBS was developed with a national normative sample of 2,855 children from 16 different states representing each of the four U.S. geographical region from the U.S. Bureau of the Census categories. The PKBS normative sample approximated the general U.S. population in terms of gender, ethnicity, and socioeconomic status. For example, 51% of the standardization sample were male and 49% were female; 80% of the sample were Caucasian and 20% were
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K. W. MerrelI and tl/1. L. Holland
members of racial or ethnic minority groups (12.1% African American, 5.2% Hispanic, 1.5% Asian or Pacific Islander, .01% American Indian, and 1.2% "other"). Based on parent occupation of the subjects (an index of socioeconomic status), similarity was found in occupational categories of the normative population when compared with the most recent occupational breakdown statistics from the U.S. Bureau of the Census. Of the 2,855 child ratings that comprised the PKBS normative sample, 51.5% of the ratings were completed by preschool teachers, kindergarten teachers, or other school personnel, whereas 48.5% were completed by parents or other caregivers (i.e., grandparents or legal guardians). Rather than being a downward extension of a rating scale designed for use with older children or adolescents, the PKBS and its items were designed specifically with the unique social-emotional aspects of the early childhood/ preschool developmental period in mind, employing systematic item development and content validation procedures. In other words, the initial item pool for the PKBS was developed following a comprehensive and systematic review of research and clinical literature describing social ~skills and behavioral-emotional problems of young children and how these problems are specifically manifested in the preschool- to kindergarten-aged range. PKBS items comprise two separate scales, each designed to measure a different domain - - a 34-item Social Skills scale, and a 42-item Problem Behavior scale. Each of these two scales includes an empirically derived subscale structure. The Social Skills scale includes the following subscales: Social Cooperation (12 items describing cooperative and self-restraint behaviors), Social Interaction (11 items reflecting social initiation behaviors), and Social Independence (11 items reflective of behaviors that are important in gaining independence within the peer group). The Problem Behavior scale includes two broad-band subscales, Internalizing Problems and Externalizing Problems. Consistent with the theoretical and empirical breakdown of the internalizing/externalizing problem dichotomy (see Cicchetti & Toth, 1991), the latter broad-band scale includes 27 items describing undercontrolled behavioral problems, such as overactivity, aggression, coercion, and antisocial behaviors, while the former broad-band scale includes 15 items describing overcontrolled behavioral/emotional problems, such as social withdrawal, anxiety, somatic complaints, and behaviors consistent with depressive symptomatology. The Externalizing Problems broad-band scale includes three narrow-band scales (Self-Centered~Explosive, Attention Problems~Overactive, and AntisocialZ4ggressive), while the Internalizing Problems broad-band scale includes two narrow-band scales (Social Withdrawal and Anxiety~Somatic Problems). The PKBS scale configuration with sample items is presented in Table 2. Research findings presented in the PKBS test manual and in other published sources provide evidence for adequate to excellent psychometric properties (reliability and validity). Internal consistency reliability estimates for the Social Skills and Problem Behavior total scores are .96 and .97, respectively. Test-
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Table 2 Scale Structure and Sample Items from the Preschool and Kindergarten Behavior Scales
Scale Numbers and Names
Sample Items
Scale A, Social Skills
A1 Social Cooperation ( 12 items) A2 Social Interaction (11 items) A3 Social Independence ( 11 items)
Shares toys and other belongings;follows rules Invites other children to play; participates in classroom or family discussions Works or plays independently;attempts new tasks before asking for help
Scale B, Problem Behavior
B1 Self-Centered/Explosive (11 items) B2 AttentionProblems/Overactive (8 items) B3 Antisocial/Aggressive (8 items) B4 Social Withdrawal (7 items) B5 Anxiety/SomaticProblems (8 items)
Has temper outbursts or tantrums; wants all the attention Acts impulsixelywithout thinking; makes noises that annoy others Is physicallyaggressive; bullies or intimidatesother children Does not respond to affection from others; avoids playing with other children Becomes sick when upset or afraid; clings to parent or caregiver
Note. Subscales BI, B2, and B3 comprise the ExternalizingProblems broad-bandscale; subscales B4 and B5 comprise the InternalizingProblems broad-bandscale.
retest reliability estimates at 3-month interw~ls were respectively found to be .69 and .78. Child ratings by preschool teachers and teacher aides for the respective total scores have been shown to correlate ;at .48 and .59. Content validity has been demonstrated through documentation of the item development procedures and through showing moderate to high correlations between individual items and total scores. Construct validity has been demonstrated through analysis of intrascale relationships, factor analytic findings with structural equation modeling (Merrell, 1996), and documentation of sensitivity to various group differences (Jentzsch & Merrell, 1996; Merrell, 1995a). Convergent and discriminant construct validity has been demonstrated through examining relationships with four other established preschool behavior rating scales, namely, the Conners Teacher Rating Scale, the Matson Evaluation of Social Skills with Young Children, the School Social Behavior Scales, and the Social Skills Rating System (Merrell, 1995b).
RESULTS The overall separation of the two groups and classification properties of the PKBS were tested using a discriminant function analysis, a multivariate procedure used to determine the accuracy of group classification based on the statistical properties of test scores. In other words, tile question answered in the
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Table 3 Subscales of the Preschool and Kindergarten Behavior Scales, with Pooled-Within-Groups Correlation Coefficients from the Discriminant Function Analysis Structure Matrix, Listed in Order of Descending Power
Scale A2 Social Interaction B4 Social Withdrawal A3 Social Independence B2 Attention Problems/Overactive AI Social Cooperation B5 Anxiety/Somatic Problems B 1 Self-Centered/Explosive B3 Antisocial/Aggressive
Correlation .78 .74 .70 .54 .51 .48 .47 .21
discriminant function is essentially "how well do the behavior rating scores from the PKBS separate and classify the DD and comparison groups?" In this analysis group membership (DD vs. Comparison) served as the grouping variable, and the eight PKBS subscale ,scores served as classification variables. The resulting discriminant function was significant, indicating that the combined PKBS scores separated and classified the two groups in a statistically significant manner: Wilks' Lambda F = .75, X2(8) = 110.92, p < .0001. The classification results table from the discriminant analysis indicated that overall, 71.36% of the children were classified correctly into their respective groups based solely on the statistical properties of the PKBS scores, including 67.3% of the DD group, and 75.4% of the Comparison group. In discriminant analysis, a structure matrix is produced, showing the relationships between the discriminating variables (in this case, the PKBS subscale scores) and the separation or classification of groups (in this case, the DD and Comparison groups). The resulting pooledwithin-groups correlations are presented in Table 3. The correlations range fi'om .21 to .78. Three PKBS subscales (A2 Social Interaction, B4 Social Withdrawal, and A3 Social Independence) were correlated substantially higher than the other subscales with the separation of the two groups, with correlations in the .70s. Following the discriminant analysis, mean PKBS scores of the two groups were compared and contrasted. A one-way analysis of variance (ANOVA) was conducted, using group membership as the independent variable and the PKBS scores as dependent variables. Descriptive statistics of the PKBS scores for the two groups are presented in Table 4, along with the F statistics and probability levels from the ANOVA. As these data indicate, all of the PKBS Social Skills scores of the DD group were significantly lower (p < .0001) than those of the comparison group, indicating that they were rated by parents and teachers as having significantly lower levels of social skills in comparison with non-DD peers. Additionally, all of the PKBS Problem Behavior scores of the DD group were significantly higher (p < .05 to p < .0001) than those of the Comparison
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Table 4 PKBS Scores of Developmentally Delayed and Matched Comparison Children: Descriptive Statistics, ANOVA Resulls, and Effect Size Estimates DD
Scale A: Social Skills Al Social Cooperation A2 Social Interaction A3 Social Independence AT Total Social Skills Scale B: Problem Behavior B 1 Self-Centered/Explosive B2 Attention Problems/Overactive B3 Antisocial/Aggressive Externalizing Total B4 Social Withdrawal B5 Anxiety/Somatic Problems Internalizing Total Total Problem Behavior
Comparison
M
SD
M
SD
F (1,396)
ES (Magnitude)
25.42 19.16 23.74 68.32
6.98 7.02 6.04 18.23
29.23 25.28 27.91 82.42
6.02 5.49 4.32 13.79
33.89** 78.79** 62.80** 75.68**
.59(medium) .90 (large) .81 (large) .88 (large)
14.35 12.33 6.78 33.45 8.47 8.67 17.14 50.59
8.43 6.21 5.86 18.93 4.42 5.11 8.5t 24.88
10.16 8.73 5.52 24.41 4.95 6.12 l 1.07 35.48
7.12 5.41 4.79 16.18 3.82 4.11 7.17 21.80
28.62** 37.93** 5.48* 26.21"* 71.89"* 30.15"* 59.12" 41.49'*
.54(medium) .62(medium) .24 (small) .51(medium) .85 (large) .55(medium) .77(medium) .63(medium)
*p < .05. **p < .0001.
group, indicating that these children were rated by parents and teachers as having significantly higher levels of both internalizing and externalizing problem behaviors in comparison with non-DD peers. The statistical power or practical significance of these differences in PKBS scores between the DD and Comparison groups was tested by computing effect size (ES) estimates, using Cohen's d method (Cohen, 1988): the mean scores of the Comparison group were subtracted from the mean scores of the DD group, and the resulting difference was divided by the harmonic standard deviation of the two groups. The resulting ES estimate (d) is interpreted as an index of how much overlap exists in the distribution of scores of each group. In other words, an effect size estimate of .50 would indicate that the mean score of one group was approximately .5 standard deviation higher than the mean score of the other group. The ES estimates are also presented in Table 4, along with conventional magnitude indicators for practical interpretation suggested by Cohen (1988), wherein small effects range from .20 to .49, medium effects range from .50 to .79, and large effects are those at or above .80. As these data indicate, all of the ES estimates for the PKBS score differences between the DD and Comparison groups had practical or clinical importance, and all but one were either at the medium or large magnitude level. The PKBS subscales with "large" effect sizes were the same ones that correlated highly with the separation of the two groups in the discriminant analysis: A2 Social Interaction (ES = .90), B4 Social Withdrawal (ES--.85), and A3 Social Independence (ES = .81).
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K. W. Merrell and M. L. Holland
Although comparisons of mean scores between groups provide valuable information regarding the overall trend and distribution of scores, they are not especially useful in describing the social-behavioral characteristics of individuals within groups. Therefore, the frequency distributions of each group were examined to determined what percentage within each group had significant social skills deficits and problem behavior excesses. The total Social Skills (A Total) and Problem Behavior (B Total) scores of each group were examined, using a clinical significance criteria of 1.5 standard deviations below the normative mean for social skills and 1.5 standard deviations above the normative mean for problem behavior. The 1.5 standard deviation criteria was used as a standard because it is often used as an efl'ective screening criterion in educational and clinical settings (Merre]l, 1994a). Using these criteria, 26.6% of the DD group but only 6% of the Comparison were identified as having significant social skills deficits, whereas 22% of the DD group but only 6% of the Comparison group were identified as having significant problem behavior excesses.
DISCUSSION The results of this study provide compelling evidence that as a group, preschoolaged children identified as having developmental delays were rated by teachers and parents as having significantly lower levels of social skills and significantly higher levels of problem behavior than children without identified developmental problems. These differences in social, emotional, and behavioral problems were both statistically significant and of practical clinical importance, as indicated by results of the inferential statistical tests and by the effect size estimates. It is interesting to consider that the PKBS scores were quite effective in classifying the DD and Comparison group participants into their respective groups, with approximately three fourths of all participants being classified correctly into their group based solely on the statistical properties of the PKBS scores. Had all of the participants in the study been classified as developmentally delayed because of problems in social-behavioral functioning, one might have anticipated such a result. However, we can only presume that the DD group was comprised of children who were classified as DD due to delayed functioning in a wide variety of areas, not just social-behavioral functioning. Thus, these results provide additional strong suppolt to previous research, which suggests that, as a group, children with developmental delays are at much higher risk than typically developing children for exhibiting deficits in social skills and excesses in a variety of behavioral and emotional problems. This risk factor is borne out by the fact that our analysis of frequency distributions indicated that being classified as having a developmental delay makes it f o u r to five times as likely that a child will have a clinically significant social skills deficit or behavioralemotional problem excess than a child who has not been identified as having a developmental delay.
Social-Emotional Behavior of Preschool Children
403
The placement or locus of the most substantial social-behavioral differences between the two groups is also intriguing. The discriminant analysis procedure and effect size calculations of PKBS scores between the two groups both indicated that three PKBS subscales stood out as showing the most powerful or strongest differences in social-emotional behavior between the two groups: A2 Social Interaction, B4 Social Withdrawal, and A3 Social Independence. The nature of the items in these three subscales share certain key characteristics and provide some additional insights into the critical differences between the two groups. Essentially, these three PKBS subscales contain items that measure a child's ability to interact successfully and independently with other children and adults. It appears that in contrast to the Comparison group, the DD group participants were rated as being particularly deficient in initiating social interactions and in working or playing independently, as well as showing excesses in avoidant and socially withdrawn behavior. Of course, it is important to remember that the PKBS scores of the DD group were significantly more problematic than those of the Comparison group in all areas, but these three related subscales represent by far the strongest differences. These results provide additional evidence for the validity of the PKBS because of the sensitivity to group differences in social-emotional behavior that was evidenced. Considered in conjunction with the other validity evidence referred to in the Method section of this paper, there appears to be mounting evidence that the PKBS is a valid and technically sound behavior rating scale for research and clinical assessment with young children. The PKBS offers the advantages of being practical, easy to use, and being targeted at the most common types of behavioral, social, and emotional problems exhibited by young children in a variety of settings. In addition to the main findings and positive aspects of this investigation, some potential limitations should also be considered. One limitation of this study was that only one method of assessment (behavior rating scales) was utilized. Because each method of assessment contains specific types of limitations and sources of error variance, it is more desirable to conduct descriptive and causal-comparative studies, such as this one using multiple types of assessment data. Related to this issue is the fact that behavior rating scales measure raters' perceptions of behavior rather than actual child behavior. One can presume that the rated perceptions of child behavior using the PKBS in this study are consistent with actual child behavior, but in the absence of supporting behavioral observation data, such a conclusion must be viewed as tentative. Use of a multimethod, multisource, multisetting assessment design (Merrell, 1994a) is the preferred optimum approach for obtaining broad-based and aggregated assessment information, and would enhance the confidence with which such results may be interpreted. Another limitation of this research is that little information regarding the subjects other than their PKBS scores and basic demographic information was available. Ideally, it would be best to know more about why the participants in
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the DD group were classified as having a developmental delay. With this data set, we can only presume that the DD participants were a heterogenous group of children who were identified and class:ified using a wide variety of criteria for a wide variety of developmental problems. The present data set does not allow for analyses and inferences regarding the potential confound of mental age, and does not shed any light on whether the PKBS is equally valid for assessing a wide range versus a restricted range of developmental delays. Additionally, it is not known how representative each of the two study groups were in relation to the larger groups (Dr) and normal children), which they were purported to sample and represent on several important variables. Additional research would help clarify some of these issues. However, it is important to recognize that the randomized block selection procedure used to select study participants from the larger data set should theoretically ensure or at least increase the probability of representativeness of the study groups (Campbell & Stanley, 19681. Finally, it is important to consider some future directions in research and clinical practice with young children who have developmental delays. Understanding the social-emotional behavior and related characteristics of these children is a very important endeavor, as is the development and refinement of technically adequate and clinically use,ful assessment instruments. However, linking knowledge and practice in these areas to effective prevention and intervention efforts is perhaps the most important challenge being faced within the field. Future research efforts that build upon tlhe present investigation in this manner will allow for increasingly important developments and refinements in effective service delivery to young children with developmental delays, disabilities, and related problems. REFERENCES Bernheimer, L. P., Keogh, B. K., & Coots, J. J. (1993). From research to practice: Support for developmental delay as a preschool category of exceptionality. Journal of Early Intervention, 17, 97-1 (16. Bracken, B. A., Keith, L. K., & Walker, K. C. (19941. Assessment of preschool behavior and socialemotional functioning: A review of thirteen third-party instruments. Assessment in Rehabilitation and Exceptionality, 1, 331-346. Brockman, L. M., Morgan, G. A., & Harmon, R. J. (1988). Mastery motivation and developmental delay. In T. D. Wachs & R. Sheenan (Eds.), Asse.~smet~'t qfyoung developmentally disabled children (pp. 267-284). New York: Plenum Press. Campbell, D. T., & Stanley, J. C. (1968). Erper.;menml and quasi-experimental mseorch design. Chicago: Rand-McNalty. Cicchetti, D., & Toth, S. L. (1991). A developmental perspeclive on internalizing and externalizing disorders. In D. Cicchetti & S. L. Toth (Eds.), lnternali=mg and externalizing expressions of dysfunction (pp. 1-19). Hillsdale, NJ: Lawrence ]Erlbaum Associates. Cohen, J. (19881. Statistical power atlalvsis ./~r the behavioral sciences (2nd. ed.). Hillsdale, NJ: Lawrence Erlbaum Associates. Copeland, M. E., & Kimmel, J. R. (19891. Evaluati~m and management q/' #zfants and young children with developmental disabilities. Baltimore, MD: Paul H. Brookes Publishing Co.
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Danaher, J. (1992). Preschool special education eligibilio" classifications and criteria. Chapel Hill, NC: National Early Childhood Technical Assistance System (NEC*TAS). (Eric Document Reproduction Service No. ED 351 847). Guralnick, M. J., & Bricker, D. (1987). The effectiveness of early intervention for children with cognitive and general developmental delays. In M. J. Guralnick & E C. Bennett (Eds.), The effectiveness ~?]' early intervention for at-risk and hamtieapped children (pp. 115-173). Orlando, FL: Academic Press, Inc. Guralnick, M. J., & Groom, J. M. (1985). Correlates of :3eer-related social competence of developmentally delayed preschool children. American Journal (!f Mental Deficiency, 90, 140-150. Guralnick, M. J., & Weinhouse, E. (1984). Peer-related social interactions of developmentally delayed young children: Development and characteristics. Developmental Psychology, 20, 815-827. Jentzsch, C. E., & MerrelL K. W. (1996). An investigation of the construct validity of the Preschool and Kindergarten Behavior Scales. Diagnostique, 21, 1-15. Kobe, E H., & Hammer, D. (1994). Parenting stress and. depression in children with mental retardation and developmental disabilities. Research in Developmental Disabilities, 15, 209-221. Kopp, C. B., Baker, B. L., & Brown, K. W. (1992). Social skills and their correlates: Preschoolers with developmental delays. American Journal on Mental Retardation, 96, 357-366. McLean, M., Smith, B. J., McCormick, K., Schakel, J., & McEvoy, M. (1991). Developmental delay: Establishing parameters fi~r a preschool eategoo' of exceptional#v. Reston, VA: Council for Exceptional Children, Division for Early Childhood. (Eric Document Reproduction Service N. ED 343 37l). Men-ell, K. W. (1994a). Assessment of behavioral, sociai, and emotional problems: Direct and objective methods for use with children and adolescents. New York: Addison Wesley/Longman. Merrell, K. W. (1994b). The Preschool and Kindergarten Behavior Scales. Austin, TX: PRO-ED. Merrell, K. W. (1995a). An investigation of the relationship between social skills and internalizing problems in early childhood: Construct validity of the Preschool and Kindergarten Behavior Scales. Journal of P.~'choeducational Assessment, 13, 230-240. Merrell, K. W. (1995b). Relationships among early childhood behavior rating scales: Convergent and discfiminant construct validity of the Preschool and Kindergarten Behavior Scales. Early Education and Development, 6, 253-264. Merrell, K. W. (1996). Assessment of social skills and behavior problems in early childhood: The Preschool and Kindergarten Behavior Scales. Journal of Early lnteta,'ention, 20, 132-145. Shaw, D. S., Keenan, K., & Vondra, J. 1. (1994). Developmental precu~ors of externalizing behavior: Ages 1 to 3. Developmental Psychology, 30, 355-364. Shonkoff, J. R, & Meisels, S. J. (1991). Defining eligibility for ser',,ices under PL 99-457. Journal ~[ Early lnteta,ention, 15, 21-25. U.S. Department of Education, Office of Special Education Programs. (1993). First-fifteenth annual reports to Congress on the implementation of the Individuals with Disabilities Education Act. Washington, DIS: Author.