Abstract
There is limited literature examining the adaptive functioning of adolescents with autism spectrum disorder (ASD). This study aimed to (a) document Vineland Adaptive Behavior Scales (VABS-3) and Adaptive Behavior Assessment System (ABAS-3) adaptive behavior profiles of adolescents with ASD; (b) examine the comparability of the two measures; and (c) assess potential discrepancies between IQ and adaptive behaviors. Participants included 14- to 18-year-olds with ASD without intellectual disability. Significant adaptive skills deficits were observed with most scores at least one standard deviation below the mean. Relative weaknesses were observed for social and daily living skills. The absolute magnitude of VABS-3 and ABAS-3 scores differed. There were significant discrepancies between IQ and adaptive functioning. These findings have implications for clinicians and researchers.
Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impairment in social communication and restricted or repetitive behaviors and interests (American Psychological Association, 2013). There is significant heterogeneity within individuals who receive this diagnosis, but one common distinction has been to categorize individuals with ASD as “without intellectual disability (ID)” or previously “high functioning” (i.e., IQ score ≥70). Such a delineation has been widely used by clinicians and researchers to mean individuals with relative strengths in language, milder symptom profiles and better long-term outcomes. However, recent work suggests that in fact there is significant variability in these youth, and that estimates from IQ alone are an imprecise proxy for functional abilities in ASD, particularly for those without ID (Alvares et al., 2020; Chatham et al., 2018). These authors argue that adaptive functioning is also critical to consider, particularly as individuals age, and that the literature suggests there may be a large discrepancy between IQ and functional abilities in individuals with ASD without ID (Alvares et al., 2020; Duncan & Bishop, 2015). In fact, adaptive abilities capture an aspect of functioning that may yield important behavioral markers and targets for intervention that are not captured by IQ (Klin et al., 2007).
Adaptive functioning encompasses behaviors critical to living independently, including daily living skills, social skills, and communication skills. Children with ASD display adaptive behavior impairments across all three domains (Liss et al., 2001), however, there is a dearth of literature investigating adaptive functioning in adolescents with ASD (Kenworthy et al., 2010; Matthews, Smith, et al., 2015). This is important as stronger adaptive functioning skills are associated with better long term outcomes in youth with ASD (Farley et al., 2009). Also, studies seem to suggest that adaptive functioning worsens with age in youth with ASD without ID and/or the gap between their IQ and adaptive behaviors grows (Kanne et al., 2011; Klin et al., 2007), which seems to reflect a stagnation in the development of functional skills with age (Matthews, Smith, et al., 2015). Thus, understanding the profile of strengths and weaknesses related to adaptive functioning in adolescents may yield new directions for intervention, which could be particularly important as there are relatively fewer interventions for older individuals with ASD (Lounds Taylor et al., 2012).
Commonly utilized measures of adaptive functioning include the Vineland Adaptive Behavior Scales (Sparrow et al., 2016) and the Adaptive Behavior Assessment System (Harrison & Oakland, 2015), which are currently in their third editions (VABS-3 and ABAS-3, respectively). The literature characterizing the adaptive functioning skills of adolescents with ASD has been based on findings from earlier editions of the VABS (Duncan & Bishop, 2015; Lee & Park, 2007; Matthews, Smith, et al., 2015) and, less frequently, the ABAS (Dupuis et al., 2020; Kenworthy et al., 2010; Pfeiffer et al., 2005). These studies generally report that adaptive functioning is impaired in adolescents with ASD (Duncan & Bishop, 2015; Dupuis et al., 2020; Kenworthy et al., 2010; Lee & Park, 2007; Matthews, Smith, et al., 2015; Pfeiffer et al., 2005). However, significant changes were made with the third editions of each including updated norms, refined items and scoring, etc. (Harrison & Oakland, 2015; Sparrow et al., 2016). Thus, it will be important to characterize the adaptive functioning of adolescents with ASD without ID on these updated measures. It will also be important to compare the two measures to one another, as previous work has shown that the second editions of these measures were not completely comparable to one another, particularly in terms of the magnitude of scores (Dupuis et al., 2020; Lopata et al., 2013), despite having similar standardization samples which approximate the US population (assessed by comparing parental education, race/ethnicity, and geographic region to the US Census data) (Harrison & Oakland, 2015; Sparrow et al., 2016). Specifically, these studies showed the VABS-II generated higher scores (i.e., less impaired adaptive functioning) than the ABAS-2 across domains (Dupuis et al., 2020; Lopata et al., 2013). This has implications for measure selection in clinical and research contexts.
The goals of the current study were to (a) document the VABS-3 and ABAS-3 adaptive behavior profiles of adolescents with ASD; (b) examine the extent to which these measures yielded similar findings on comparable scales; and (c) assess potential discrepancies between cognitive ability and adaptive behaviors. We utilized similar analytical methodology as a previous study comparing the VABS-II and ABAS-2 (Lopata et al., 2013) with an older sample of adolescents (aged 14 to 18 years) diagnosed with ASD without ID. Given the literature we expected that adolescents with ASD would demonstrate poorer adaptive functioning than would be expected given their IQ. Further, we expected that the VABS-3 would yield higher scores than the ABAS-3.
Methods
Participants
Participants included 62 adolescents diagnosed with ASD. Their baseline data was drawn from an ongoing clinical trial investigating a daily living skills intervention. Inclusion criteria for the primary study included: (1) between the ages of 14–21 and enrolled in high school; (2) a diagnosis of ASD based on the Autism Diagnostic Observation Schedule, 2nd Edition (Lord et al., 2012) and a previous diagnosis of ASD from a medical provider; (3) a full scale IQ ≥ 70 based on the Abbreviated Battery of the Stanford Binet Intelligence Scales, 5th Edition (Roid, 2003). Demographic characteristics of the sample are reported in Table 1.
Table 1.
Sample Demographic Characteristics (n=62)
| Characteristic | M (SD) |
|---|---|
| Age in years | 16.53 (1.22) |
| SB5 Abbreviated IQa Standard Score | 97.40 (10.32) |
| SB5 Vocabulary Scaled Score | 9.40 (2.56) |
| SB5 Object Series/Matrices Scaled Score | 9.52 (2.51) |
| n (% of total) | |
| Male | 43 (69.4%) |
| Race | |
| Asian | 1 (1.6%) |
| Black or African American | 8 (12.9%) |
| White | 49 (79.0%) |
| More Than One Race | 3 (4.8%) |
| Other | 1 (1.6%) |
| Hispanic or Latino | 3 (4.8%) |
| Caregiver 1’s Highest Level of Education | |
| Some College/Associate Degree | 21 (33.8%) |
| Baccalaureate Degree | 20 (32.3%) |
| Graduate/Professional | 18 (29.0%) |
| High School Graduate/GED Diploma | 2 (3.2%) |
| Annual Household Income | |
| Less than or equal to $50,000 | 13 (21.0%) |
| $51,000 - $100,000 | 22 (35.5%) |
| $101,000 - $160,000 | 17 (27.4%) |
| Over $160,000 | 8 (12.9%) |
| Not listed | 2 (3.2%) |
Note:
ABIQ available for 57 of 62 participants
Measures
Vineland Adaptive Behavior Scales, Third Edition (VABS-3)
The VABS-3 is comprehensive adaptive behavior measures that yields composite standard scores in three domains: Communication, Daily Living Skills, and Socialization (Sparrow et al., 2016). These three core domain scores together make up the Adaptive Behavior Composite score. Items are organized in a developmental succession within each subdomain and each item is rate on a 3-point scale as 0 (never), 1 (sometimes), and 2 (usually) performs a behavior. The Communication domain assesses behaviors needed to communicate with others both verbally and through writing (Receptive, Expressive, and Written subdomains). The Daily Living Skills domain assesses behaviors needed to be self-sufficient in personal care, housekeeping, and functioning in the community (Personal, Domestic, and Community subdomains). The Socialization Domain assesses behaviors needed to participate in interpersonal relationships, engage in activities with others, and respond appropriately in situations with others (Interpersonal Relationships, Play and Leisure, and Coping Skills subdomains). In the current study, a computer assisted semi-structured interview was utilized. Reliability of the VABS-3 was based on and consistent across all three methods of administration (i.e., interview, paper, and online). The domain standard scores in each of the Comprehensive forms and the Adaptive Behavior Composite scores performed well on indexes of internal consistency, test-retest reliability, and interrater/inter-interviewer reliability (Sparrow et al., 2016). Scores on the VABS-3 correlated with other adaptive behavior instruments, including the ABAS-3 (Sparrow et al., 2016).
Adaptive Behavior Assessment System, Third Edition (ABAS-3)
The ABAS-3 measures adaptive behavior in three domains, Conceptual, Practical, and Social, as assessed by the parent/primary caregiver (Harrison & Oakland, 2015). Items are rated as 1 (never), 2 (sometimes), and 3 (always) performs the behavior as needed or as 0 (not able to perform the behavior). The Conceptual domain assesses behaviors needed to communicate with others, apply academic skills, and manage and accomplish tasks (Communication, Functional Pre-Academics, and Self-Direction adaptive skill areas). The Practical domain assesses behaviors needed to address personal and health needs, take care of home, classroom, and work settings, and function in a community (Community Use, Home Living, Health and Safety, and Self Care adaptive skill areas). The Social domain assesses behaviors needed to engage in interpersonal interactions, act with social responsibility and use leisure time (Social and Leisure adaptive skill areas). Together these three domain scores make up the General Adaptive Composite which provides an overall estimate of adaptive behavior. Reliability of the ABAS-3 was examined from several perspectives, with the adaptive skill area scaled scores, adaptive domain standard scores, and General Adaptive Composite scores performing well on indexes of internal consistency, standard error of measurement, test-retest reliability, interrater reliability, cross-form consistency, and alternative-forms reliability (Harrison & Oakland, 2015). The scales and composite scores correlated in expected ways with scores from the ABAS-2 and VABS-II, providing evidence of convergent validity. Finally, ABAS-3 scores distinguish typically developing individuals from those with ASD (Harrison & Oakland, 2015).
Abbreviated Battery of the Stanford Binet Intelligence Scales, 5th Edition
The Abbreviated Battery of the Stanford Binet Intelligence Scales, 5th Edition (SB5) (Roid, 2003) was used to provide an estimate of IQ. At the beginning of every SB5 administration, participants complete two “routing” subtests: one nonverbal (object series/matrices) and one verbal (vocabulary). The purpose of routing is to determine the starting level for subsequent nonverbal and verbal subtests delivered as part of the full SB5 assessment; however, scores from the routing subtests can be combined to produce an abbreviated IQ score. The abbreviated IQ can serve as an estimate of full scale IQ given that strong ABIQ-full scale IQ associations emerged for the SB5 standardization sample and in studies involving children and adolescents with ASD (Coolican et al., 2008; Matthews, Pollard, et al., 2015; Roid, 2003), although it should be noted that it may underrepresent abilities given that some children scored higher on the Full Scale IQ than abbreviated IQ (Coolican et al., 2008). The Full Scale IQ and the abbreviated IQ scores performed well on indexes of internal consistency, standard error of measurement, test-retest stability, and inter-scorer agreement reliability. Evidence for the validity of the SB5 was provided by test content validation, confirmatory factor analysis, and concurrent administrations of other measures of cognitive ability (Roid, 2003). The abbreviated IQ is also strongly associated with overall IQ scores on other widely-used cognitive assessment measures (Roid, 2003).
Procedures
This study was approved by the Institutional Review Board and conducted in compliance with the approved protocol. Each adolescent was screened using a structured protocol and met clearly defined inclusion criteria. Prior to participation in an intervention, parents participated in a computer assisted semi-structured VABS-3 interview via an iPad, and then completed the ABAS-3 Parent/Caregiver Rating Forms. Each VABS-3 and ABAS-3 protocol was scored using the appropriate computer scoring program. Scores from all measures were entered into a database. All measures were administered on the same day by trained administrators who were supervised by clinical psychologists.
Analytical Approach
Within-Measure Profile Comparisons
In order to explore the profile of adaptive behavior within each measure for the sample (e.g., do adolescents have more deficits in, for example, the socialization domain compared to the daily living skills domain), within-measure profile comparisons were conducted. Using dependent samples t-tests, each of the nine subdomain v-scale scores of the VABS-3 was compared to the average of the other eight remaining subdomain v-scale scores for statistical significance. As described by Lopata et al. (2013), “this analytic method is consistent with the ipsative approach used for profile analysis in clinical practice, and it reduced the number of required subdomain comparisons to nine” (pp. 5). The three adaptive domain scores (i.e., Communication, Daily Living Skills, and Socialization) were compared to each other via one-way within-subjects ANOVA.
The same statistical approach was utilized for the nine skill areas and the three adaptive domain composite scores (i.e., Conceptual, Practical, and Social) on the ABAS-3.
Inter-correlations
Pearson’s correlations were computed between the VABS-3, ABAS-3, and SB-5 ABIQ scores.
Cross-Measure Comparisons
In order to explore the correspondence between the VABS-3 interview and ABAS-3 rating scale, which has implications for the clinical and research utility of these measures in documenting impairment (Dupuis et al., 2020), we directly compared the two measures to one another. The VABS-3 v-scale and ABAS-3 adaptive skill area scaled scores are on different metrics. In order to facilitate a direct comparison between the two measures, the VABS-3 v-scale and ABAS-3 adaptive skill area scaled scores were converted to a common metric (a deviation quotient metric with a normative M = 100 and normative SD = 15). We then compared the most “logically equivalent” adaptive scores [as identified by Lopata et al. (2013)] across the VABS-3 and ABAS-3 using dependent samples t-tests. See Table 2 for a description of the subscales.
Table 2.
Subscale Descriptions of the VABS-3 and ABAS-3
| VABS-3 | ABAS-3 | ||
|---|---|---|---|
| Communication Domain | Conceptual Domain | ||
| Expressive | Using words and sentences to express oneself verbally to others. | Communication | Speech, language, and listening skills needed for communication with other people. |
| Written | Using reading and writing skills. | Functional Academics | Basic skills that form the foundations of reading, writing, mathematics, and other skills needed for daily, independent functioning. |
| Socialization Domain | Social Domain | ||
| Interpersonal | Responding and relating to others, including friendships, caring, social appropriateness, and conversation. | Social | Skills needed for interacting socially and getting along with other people. |
| Play and Leisure | Engaging in play and fun activities with others. | Leisure | Skills needed for engaging in and planning leisure and recreational activities. |
| Coping | Demonstrating behavioral and emotional control in different situations involving others. | Self-Direction | Skills needed for independence, responsibility, and self-control. |
| Daily Living Skills Domain | Practical Domain | ||
| Personal | Self-sufficiency is such areas as eating, dressing, washing, hygiene, and health care. | Self-Care | Skills needed for personal care. |
| Domestic | Performing household tasks such as cleaning up after oneself, chores, and food preparation. | Home Living | Skills needed for basic care of a home or living setting. |
| Community | Functioning in the world outside the home, including safety, using money, travel, rights and responsibilities, etc. | Community Use | Skills needed for functioning and performing important behaviors in the community. |
IQ versus Adaptive Behavior Discrepancies
Mean differences between the Abbreviated Battery of the SB5 abbreviated IQ score and each of the eight adaptive behavior summary scores (i.e., one composite and three domain scores from the VABS-3, and one composite and three domain scores from the ABAS-3) were assessed using dependent samples t-tests.
Correction for Multiple Comparisons
The overall, experiment-wise alpha level was kept at .05 using a Bonferroni-corrected, per-comparison alpha level of .001 (two-tailed) across all three sets of analyses.
Results
Within-Measure Profile Comparisons
Means and standard deviations for each subscale, domain, and composite score by instrument are listed in Table 3. All scores in Table 3 are reported in their original metric, and they document the adaptive behavior profile of the adolescents on each measure. The VABS-3 composite and domain scores were all <70 which are classified qualitatively as Low, and the VABS-3 v-scale scores were all in the Low (Expressive, Personal, Domestic, Interpersonal, Play and Leisure) or Moderately Low (Written, Receptive, Community, and Coping) range. The ABAS-3 domain and composite scores were all in the Low range with the exception of Conceptual which was at the lower end of the Below Average range. Similarly, the ABAS-3 adaptive skill area scaled scores were all in the Low (Community Use, Leisure, and Social) or Below Average (Communication, Functional Academics, Home Living, Health and Safety, Self-Care, and Self-Direction) range.
Table 3.
Descriptive Data in the Original Metrics for the VABS-3 and ABAS-3
| VABS-3 (n = 62) | ABAS-3 (n = 60) | ||
|---|---|---|---|
| Domaina | M (SD) | Domaina | M (SD) |
| Communication | 68.97 (13.21) | Conceptual | 81.33 (8.69) |
| Daily Living Skills | 61.98 (19.15) | Practical | 78.00 (9.67) |
| Socialization | 64.65 (14.09) | Social | 76.62 (9.46) |
| Adaptive Behavior Composite | 64.98 (11.79) | General Adaptive Composite | 77.15 (8.82) |
| Subdomain v-scaleb | Skill Area – scaled scorec | ||
| Expressive | 8.32 (3.67) | Communication | 6.50 (1.81) |
| Receptive | 9.56 (2.87) | Community Use | 5.72 (2.71) |
| Written | 11.90 (2.76) | Functional Academics | 7.45 (2.25) |
| Personal | 8.52 (3.37) | Home Living | 6.35 (1.85) |
| Domestic | 8.82 (3.20) | Health and Safety | 7.58 (2.65) |
| Community | 9.92 (2.31) | Leisure | 4.27 (2.28) |
| Interpersonal | 7.87 (2.56) | Self-Care | 6.65 (2.07) |
| Play and Leisure | 8.52 (3.42) | Self-Direction | 6.17 (2.03) |
| Coping | 9.45 (3.60) | Social | 5.32 (2.35) |
Domain/Composite Scores for both VABS-3 and ABAS-3 have a M = 100 and SD = 15
VABS-3 v-scale scores have a M = 15 and SD = 3.
ABAS-3 skill area scaled scores have a M = 10 and SD = 3.
Vineland Adaptive Behavior Scales, Third Edition (VABS-3)
Results of the dependent samples t-tests indicated that the VABS-3 Interpersonal v-scale was significantly lower (p < .001), while the Written v-scale was significantly higher (p < .001) than the respective averages of the other subdomains. The seven remaining subdomains were not significantly different (p > .05 in each case) than the respective averages of the other subdomains.
For the VABS-3 composite scores, the omnibus F-test was significant ([2, 40] = 3.79, p =.026). Bonferroni-corrected post-hoc comparisons indicated that the Communication domain was significantly higher than the Daily Living Skills domains. The Daily Living Skills (p = .850) and Communication (p = .452) domains did not differ significantly from the Socialization domain.
Adaptive Behavior Assessment System, Third Edition (ABAS-3)
Results of the dependent samples t-tests indicated that the Leisure and Social subdomains were significantly lower (p < .001), while the Functional Academics and Health and Safety subdomains were significantly higher (p < .001) than the respective averages of the other subdomains. The five remaining subdomains were not significantly different (p > .02 in each case) than the respective averages of the other subdomains using the Bonferroni-corrected .001 alpha.
For the ABAS-3 adaptive domain scores, the omnibus F-test was significant ([2, 40] = 10.80, p < .001). Bonferroni-corrected post-hoc comparisons indicated that the Conceptual domain score was significantly higher than the Social (p = .003) and Practical (p = .003) domain scores, which did not differ significantly from one another (p = 1.0).
Inter-correlations
Pearson’s correlations were computed for the VABS-3, ABAS-3, and SB-5 abbreviated IQ scores (see Table 4). In examining the correlations between adaptive behavior composite scores, the VABS-3 Adaptive Behavior Composite score was highly correlated (defined as a correlation ≥ .6) with the ABAS-3 General Adaptive Composite (r = .64). In terms of correlations between VABS-3 and ABAS-3 Domain scores, the VABS-3 Socialization Domain score was highly correlated with the ABAS-3 Social Domain Score (r = .62), and the VABS-3 Daily Living Skills was highly correlated with the ABAS-3 Practical (r = .61) and Conceptual (r = .59) Domain scores. As can be seen in Table 4 (bolded values), there were significant and large positive correlations between the “logically equivalent” subtests of the VABS-3 and ABAS-3, with the exception that the VABS-3 Communication Domain score was only moderately correlated with the ABAS-3 Conceptual Domain score (r = .3). Notably, however, there were significant positive correlations between multiple VABS-3 v-scale and ABAS-3 adaptive domain scores. Interestingly, the abbreviated IQ score was not significantly correlated with the ABAS-3 adaptive domain scores (except the conceptual domain and functional academics at a relatively low magnitude), but was significantly correlated with multiple VABS-3 scores (only VABS-3 Socialization Domain, Interpersonal v-scale and Play and Leisure v-scale scores were not significantly correlated with the abbreviated IQ score).
Table 4.
Inter-Correlations
| GAC | CON | COM | ACA | SOCD | SOC | LEI | SDIR | PRAC | SELF | HOME | CMY | HSFY | ABIQ | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ABC | .64** | .65** | .56** | .55** | .46** | .46** | .41** | .56** | .58** | .48** | .46** | .41** | .46** | .40** |
| COM | .38** | .50** | .40** | .41** | .12 | .16 | .08 | .43** | .36** | .32** | .33** | .24 | .27* | .49** |
| EXP | .24 | .35** | .30** | .30* | .09 | .12 | .05 | .25 | .20 | .09 | .16 | .25 | .13 | .27* |
| WRI | .46** | .59** | .48** | .60** | .23 | .22 | .24 | .42** | .40** | .30* | .24 | .28* | .41** | .58** |
| SOC | .58** | .54** | .55** | .35** | .62** | .62** | .55** | .54** | .44** | .30* | .35* | .33* | .39** | .14 |
| INT | .43** | .43** | .47** | .22 | .56** | .61** | .46** | .44** | .24 | .19 | .20 | .21 | .17 | −.15 |
| PLAY | .50** | .48** | .56** | .32* | .53** | .48** | .52** | .40** | .36** | .22 | .28* | .30* | .31* | .29* |
| COP | .52** | .46** | .37** | .32* | .52** | .54** | .45** | .53** | .44** | .26* | .32* | .29* | .46** | .12 |
| DLS | .60** | .59** | .45** | .58** | .36** | .34** | .35** | .46** | .61** | .51** | .46** | .45** | .46** | .38** |
| PER | .49** | .45** | .32** | .44** | .26* | .27* | .21 | .37** | .54** | .56** | .41** | .35** | .41** | .26* |
| DOM | .47** | .42** | .37** | .39** | .30* | .32* | .25 | .33* | .50** | .42** | .56** | .24 | .37** | .38** |
| CMY | .41** | .54** | .36** | .55** | .19 | .17 | .24 | .39** | .35** | .11 | .10 | .50** | .31* | .37** |
| ABIQ | .20 | .30* | .25 | .36** | −.07 | −.07 | −.02 | .16 | .23 | .16 | .19 | .17 | .21 | n/a |
Note. VABS-3 abbreviations (first column): ABC = Adaptive Behavior Composite; COM = Communication Domain; EXP = Expressive; WRI = Written; SOC = Socialization Domain; INT = Interpersonal; PLAY = Play and Leisure; COP = Coping; DLS = Daily Living Skills Domain; PER = Personal; DOM = Domestic; CMY = Community. ABAS-3 abbreviations (first row): GAC = General Adaptive Composite; CON = Conceptual Domain; COM = Communication; ACA = Functional Academics; SOCD = Social Domain; SOC = Social; LEI = Leisure; SDIR = Self-Direction; PRAC = Practical Domain; SELF = Self-care; HOME = Home Living; CMY = Community Use; HSFY = Health and Safety; ABIQ = SB5 Abbreviated IQ Score. Bolded values indicate the correlations between “logically equivalent” subtests.
Cross-Measure Comparisons
The VABS-3 scores were significantly lower than the ABAS-3 scores for all cross-measure comparisons, with the exception of the VABS-3 Written and ABAS-3 Functional Academics and the VABS-3 Play and Leisure and ABAS-3 Leisure domains using the Bonferroni-corrected .001 alpha (Table 5). The magnitude of score differences between the measures was quite large (range of 3 to 16 points), with the largest discrepancies observed for VABS-3 Communication versus ABAS-3 Conceptual and the VABS-3 Daily Living Skills versus ABAS-3 Practical composites.
Table 5.
Cross-Measure Comparisons of the VABS-3 and ABAS-3 Scores Transformed to a Common Metric
| VABS-3 | ABAS-3 | |||
|---|---|---|---|---|
| Domain/subdomain/composite | M (SD) | Domain/skill area/composite | M (SD) | |
| Adaptive Behavior Composite | 65.25 (11.61) | General Adaptive Composite | 77.15 (8.82) | t(59) = −10.15, p<.000 |
| Communication Domain | 69.15 (13.16) | Conceptual Domain | 81.33 (8.69) | t(59) = −8.13, p<.000 |
| Expressive | 67.17 (18.02) | Communication | 82.50 (9.04) | t(59) = −6.75, p<.000 |
| Written | 84.67 (13.90) | Functional Academics | 87.25 (11.25) | t(59) = −1.73, p = .088 |
| Socialization Domain | 64.55 (14.16) | Social Domain | 76.62 (9.46) | t(59) = −8.39, p<.000 |
| Interpersonal | 64.42 (12.92) | Social | 76.58 (11.73) | t(59) = −8.58, p<.000 |
| Play and Leisure | 67.58 (17.36) | Leisure | 71.33 (11.38) | t(59) = −1.92, p = .058 |
| Coping | 71.83 (17.56) | Self-Direction | 80.83 (10.13) | t(59) = −4.67, p<.000 |
| Daily Living Skills Domain | 62.73 (18.67) | Practical Domain | 78.00 (9.67) | t(59) = −7.92, p<.000 |
| Personal | 68.33 (16.36) | Self-Care | 83.25(10.37) | t(59) = −8.45, p<.000 |
| Domestic | 69.75 (15.63) | Home Living | 81.75 (9.24) | t(59) = −7.17, p<.000 |
| Community | 74.67 (11.75) | Community Use | 78.58 (13.56) | t(59) = −2.38, p = .021 |
| Health and Safety | 87.92 (13.25) | n/a | ||
Note. VABS-3 v-scale and ABAS-3 skill area scaled scores transformed to be on same scale using deviation quotient transformation with a normative mean of 100 and normative standard deviation of 15.
IQ versus Adaptive Behavior Discrepancies
Means for all eight adaptive behavior composites and domain scores were significantly lower (p < .001) than the abbreviated IQ (M = 97.40). Discrepancies ranged from 16.07 points (ABAS-3 Conceptual domain) to 35.02 points (VABS-3 Daily Living Skills domain; see Table 6).
Table 6.
Discrepancies between Abbreviated IQ and Adaptive Behavior Scores
| Domain/Composite | Standard Score (M = 100) | Discrepancy |
|---|---|---|
| VABS-3 | ||
| Communication Domain | 68.97 | 28.43** |
| Socialization Domain | 64.65 | 32.75** |
| Daily Living Skills Domain | 61.98 | 35.42** |
| Adaptive Behavior Composite | 64.98 | 32.42** |
| ABAS-3 | ||
| Conceptual Domain | 81.33 | 16.07** |
| Social Domain | 76.62 | 20.78** |
| Practical Domain | 78.00 | 19.40** |
| General Adaptive Composite | 77.15 | 20.25** |
Note. Discrepancies were based on the differences between the group average Abbreviated IQ (M = 97.40, SD = 10.32) and the domain/composite score from the adaptive measures.
p <.001
Discussion
The aims of the current study were threefold. We set out to (a) document the VABS-3 and ABAS-3 adaptive behavior profiles of adolescents with ASD; (b) examine the extent to which these measures yielded comparable findings; and (c) assess potential discrepancies between cognitive ability and adaptive behaviors. This is one of few studies investigating adaptive functioning in a narrowly defined age range (14 to 18 years) of adolescents with ASD without ID. We found that the adaptive functioning of adolescents with ASD without ID is impaired across domains, regardless of whether the VABS-3 or ABAS-3 is utilized. However, cross-measure comparisons on deviation quotient transformed scores revealed that the VABS-3 yielded lower scores (by up to 16 points or one standard deviation) than the ABAS-3 on almost all domains. Notably, although the VABS-3 and ABAS-3 subscale and domain scores presumably measuring similar constructs were at least moderately correlated, there were also moderate correlations between scales measuring dissimilar constructs which indicates a dearth of clear support for logical similarity across certain scales across measures. Adaptive functioning was significantly lower than what would be expected given the adolescents’ cognitive abilities, and this discrepancy was particularly large when compared to VABS-3 domain scores (i.e., ≥ 2 standard deviation difference).
Within the VABS-3, the Daily Living Skills score was found to be significantly lower than the Communication domain score, but neither differed significantly from the Socialization score. The extant literature with regards to VABS Daily Living Skills compared to Communication is mixed with some studies reporting comparable scores for Daily Living Skills and Communication (Dupuis et al., 2020; Lopata et al., 2013), and others reporting lower Daily Living Skills than Communication (Klin et al., 2007; Liss et al., 2001; Matthews, Smith, et al., 2015) scores. Similarly mixed findings are reported for Socialization scores although generally, Socialization scores are lower than Communication and either lower than (Duncan & Bishop, 2015; Dupuis et al., 2020; Kenworthy et al., 2010; Lee & Park, 2007; Lopata et al., 2013; Matthews, Smith, et al., 2015) or comparable to (Klin et al., 2007; Liss et al., 2001) Daily Living Skills scores. Notably, only one of these studies focused exclusively on adolescents (Duncan & Bishop, 2015); developmental differences may be contributing to the mixed findings. Also, the Daily Living Skills items were updated for the third edition of the VABS (e.g., adding items about use of technology) making it difficult to directly compare the current findings to much of the literature. Additionally, the fact that the data for this study was drawn from an ongoing clinical trial investigating a daily living skills intervention may partially explain why the scores on the Daily Living Skills domain were particularly low in this sample (M = 60.86).
Within the ABAS-3, the Conceptual composite score was higher than the Practical and Social composites, which is consistent with a previous study using the ABAS-2 with adolescents and young adults (Kenworthy et al., 2010). Of note, the magnitude of ABAS composite scores in the Kenworthy et al. (2010) study and the current study are quite similar. However, in a study with a wider age range, similar scores for the ABAS-II Conceptual and Social composites, which were both higher than the Practical composite, were reported (Dupuis et al., 2020); ABAS-II scores in the Dupuis et al. (2020) study were all <70 (i.e., lower than ABAS-3 scores obtained in the current study). Taken together these findings suggest that, in addition to the expected challenges related to social functioning, adolescents with ASD without ID appear to have a particular deficit in the Practical domain, which includes the skill areas of self-care, home living, community use, health and safety, and work. This gives credence to the hypothesis that basic and instrumental daily living skill deficits become more pronounced during adolescence and young adulthood for individuals with ASD without ID (Lopata et al., 2013). Daily living skills are neither a core deficit of ASD nor as confounded with social–communication skills as other areas of adaptive behavior (Duncan & Bishop, 2015). Thus the low scores in the Practical domain (taken together with low scores for VABS-3 Daily Living Skills) are concerning, particularly as daily living skills are highly associated with positive adult outcomes (Farley et al., 2009).
Although both the VABS-3 and ABAS-3 scores showed significantly impaired adaptive functioning for the adolescents with ASD without ID, the cross-measure comparisons showed that the ABAS-3 revealed lower levels of impairment than the VABS-3 (i.e., most scores on the VABS-3 were <75 while most scores on the ABAS-3 were >75; see Table 3). This was unexpected given the two previous studies directly comparing the second edition of these measures reported the opposite pattern of findings, with the ABAS-2 revealing higher levels of impairment than the VABS-II (Dupuis et al., 2020; Lopata et al., 2013). The fact that the VABS-3 was completed using the computer assisted semi-structured interview which prompts the interviewer to ask specific probes based on the parent’s response may explain the discrepancy. For example, the probes and scoring criteria on the VABS-3 may have led to a more comprehensive understanding of the adolescent’s skills when scoring each item. Additionally, the inter-correlations table suggests only moderate correlations between scores measuring presumably similar constructs and also moderate correlations for those measuring presumably dissimilar constructs (e.g., ABAS-3 Functional Academics and VABS-3 Community). Thus, future work examining items at the item level may be important to better understand the correspondence of the two measures. Alternatively, developmental differences may be at play such that the VABS-3 and ABAS-3 perform differently for adolescents as compared to children. More research is needed to explore this hypothesis. Finally, it should be noted that the VABS-3 scores were lower in a study directly comparing the VABS-II and VABS-3 in individuals with neurodevelopmental disorders (Farmer et al., 2020) and that ABAS-3 scores were higher than ABAS-2 scores in a study comparing the two measures in a mixed clinical sample of children (von Buttlar et al., 2021); these findings may partially explain the discrepancy between studies comparing the VABS-II and ABAS-2 with the current findings.
A cognitive functioning advantage over adaptive functioning in children and adolescents with ASD has been repeatedly documented (Alvares et al., 2020; Chatham et al., 2018; Kanne et al., 2011; Lopata et al., 2013; Matthews, Smith, et al., 2015) and we showed this same pattern. Thus, while these adolescents have relatively intact cognitive skills, they are unable to translate this into successful adaptive functioning across multiple domains. Interestingly, however, the discrepancy between IQ and adaptive functioning was less for the ABAS-3 than the VABS-3. These results may be particularly relevant to clinicians and researchers who work with adolescents with ASD without ID. Specifically, it may be beneficial to continue to use the VABS-3 if it has been used in previous assessments and can document progress, strengths, and challenges in adaptive behavior. However, the ABAS-3 may be useful for treatment planning due to the number and breadth of adaptive behavior items that are developed and mastered in adolescence and young adulthood. The ABAS-3 also has a self-report form for individuals over the age of sixteen.
Limitations
This study is not without limitations. As noted earlier, the different administration formats of the ABAS-3 (survey) and VABS-3 (computer assisted semi-structured interview) may have affected scores on the two measures. Additionally, while we had a relatively large homogeneous sample of adolescents with ASD without ID and employed stringent alpha corrections, a larger sample size would have been ideal given the number of statistical comparisons. It would be ideal to have a more diverse sample (sex, ethnicity/race) to improve the generalizability of findings. Finally, generalizability to adolescents with ASD without ID may be limited by the fact that all participants were recruited from an ongoing clinical trial and enrolled in high school.
Conclusions
These findings suggest that adaptive functioning is impaired in adolescents with ASD without ID, regardless of which adaptive functioning measure is employed, and that their performance across domains is lower than what would be expected given their average cognitive abilities. The results highlight the need for interventions to address adaptive behavior deficits in adolescents with ASD without ID in order to increase the likelihood of a successful adult outcome. In addition to the expected challenges with social skills given the ASD diagnosis, particular weaknesses were observed for basic and instrumental daily living skill deficits, which appear to be more pronounced during adolescence. As daily living skills are potentially mutable, they may be a candidate target for interventions directed towards adolescents (Duncan et al., 2018; Duncan & Bishop, 2015). Notably, the VABS-3 and ABAS-3 scores are not directly equivalent, and higher scores on the ABAS-3 may contribute to variations in adaptive function classification from those obtained using the VABS-3. It is beyond the scope of this study to explore which measure provided a more accurate reflection of the adaptive functioning of the individual, the higher ABAS-3 scores or the lower VABS-3 scores. Unfortunately, there is no external gold standard for evaluation of adaptive behavior, so we are unable to judge their respective validity. Depending on the purpose (e.g., diagnosis, treatment planning, qualification for services, research, etc.) and age of the sample, clinicians and researchers may opt to use one measure over the other.
Acknowledgments
The authors have no conflicts of interest to disclose. This work was supported by the Department of Defense (grant #W81XWH-17-ARP) and Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD grant #K23HD094855-01A1). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Footnotes
Conflict of Interest: All authors declare they have no conflicts of interest.
Ethical approval: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Consent to participate: Informed consent and assent was obtained from all individual participants included in the study.
Data repository: Data from this study has been submitted to the National Institutes of Health funded data repository, the National Database for Autism Research (NDAR).
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