ORIGINAL RESEARCH

published: 11 August 2021

doi: 10.3389/fpsyg.2021.692330

Adaptive Behavior as an Alternative

Outcome to Intelligence Quotient in
Studies of Children at Risk: A Study
of Preschool-Aged Children in Flint,
MI, USA
Shuting Zheng 1*, Kaja LeWinn 1 , Tiffany Ceja 2 , Mona Hanna-Attisha 2,3 , Lauren O’Connell 2,3
and Somer Bishop 1
1
Department of Psychiatry and Behavioral Sciences, Weill Institute for Neurosciences, University of California, San Francisco,
San Francisco, CA, United States, 2 Division of Public Health, Pediatric Public Health Initiative, Michigan State University, Flint,
Edited by: MI, United States, 3 Department of Pediatrics and Human Development, Michigan State University, East Lansing, MI,
Yoshifumi Ikeda, United States
Joetsu University of Education, Japan

Reviewed by: Intelligence quotient (IQ) is commonly measured in child development studies, while
James Patton,
adaptive behavior is less frequently considered. Given its associations with functional
University of Texas at Austin,
United States outcomes in children with neurodevelopmental disabilities, adaptive behavior may
Erica Neri, be a useful outcome in general population samples, as well. This study aimed to
University of Bologna, Italy
compare social and environmental correlates of adaptive behavior vs. IQ in a sample
*Correspondence:
Shuting Zheng
of preschoolers exposed to the Flint water crisis (N = 184). Mother–child dyads were
shuting.zheng@ucsf.edu recruited from the community and administered a comprehensive battery to obtain
information about child neurodevelopmental functioning, including direct assessment
Specialty section:
This article was submitted to
of IQ via the Wechsler Preschool and Primary Scale of Intelligence and assessment of
Developmental Psychology, parent-reported adaptive functioning via the Vineland Adaptive Behavior Scales. Multiple
a section of the journal social environmental factors were explored as potential correlates of child outcomes (i.e.,
Frontiers in Psychology
IQ and adaptive behavior), and robust correlates were identified using a data-driven
Received: 08 April 2021
Accepted: 09 July 2021 approach [i.e., least absolute shrinkage and selection operator (LASSO) regression].
Published: 11 August 2021 We then examined associations between the LASSO-selected predictors and IQ and
Citation: adaptive behavior while controlling for child age, child sex, and maternal age. Children in
Zheng S, LeWinn K, Ceja T,
this sample showed relative strength in adaptive behaviors, with scores in the adequate
Hanna-Attisha M, O’Connell L and
Bishop S (2021) Adaptive Behavior as range, while average IQs fell in the low-average range. Adaptive behavior was significantly
an Alternative Outcome to Intelligence associated with maternal nurturance practices, while IQ was associated with the maternal
Quotient in Studies of Children at Risk:
A Study of Preschool-Aged Children in education level. Implications for the use of adaptive behavior as an outcome measure in
Flint, MI, USA. studies of children at an increased risk for neurodevelopmental problems are discussed.
Front. Psychol. 12:692330.
doi: 10.3389/fpsyg.2021.692330 Keywords: adaptive behavior, IQ, nurturance, maternal education, modifiable predictors

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Zheng et al. IQ and Adaptive Behavior Correlates

INTRODUCTION 2011). However, rather than providing a “pure” measure of

ability, IQ scores may reflect a multitude of factors beyond the
Adaptive behavior is defined as the conceptual, social, and innate cognitive capacity of an individual (Croizet and Dutrévis,
practical skills that are needed to function within his/her 2004; Fagan and Holland, 2007; Kendler et al., 2015; Ritchie
environment of an individual in everyday life (Schalock et al., and Tucker-Drob, 2018). For example, IQ has consistently
2021). Historically, adaptive behavior has been a central point been shown to be related to socioeconomic status (SES)
of discussion for nosology and outcomes in individuals with variables, especially maternal education and household income
intellectual and developmental disabilities (Luckasson et al., levels (Duncan and Brooks-Gunn, 2000; National Institute of
2002; National Research Council (US) Committee on Disability Child Health Human Development Early Child Care Research
Determination for Mental Retardation et al., 2002; Alexander Network, 2005; Nelson et al., 2007; Tucker-Drob et al., 2013;
and Reynolds, 2020). In fact, while evidence of a low intelligence Kendler et al., 2015; LeWinn et al., 2020). Moreover, as a
quotient (IQ) is still required for a diagnosis of intellectual measured construct, IQ has a number of well-known limitations
disability (ID; previously called mental retardation), DSM-5 that have sparked historical debate and controversy. Specifically,
currently stipulates that the level of ID (i.e., mild, moderate, early studies introduced serious questions about why racially
severe, and profound) should be based on adaptive functioning and culturally diverse groups scored lower in the knowledge
rather than IQ (American Psychiatry Association, 2013). This of learned information on IQ measures and raised concerns
reflects the understanding that although cognitive and adaptive about cross-cultural validity of IQ tests given cultural differences
functioning is correlated, the capacity to acquire a given skill in conceptualizations of intelligence (Jensen, 1980; Helms,
may be different than the likelihood of actually executing that 1992; Rushton and Jensen, 2005; Sternberg et al., 2005; Fagan
skill in everyday life (Sparrow and Cicchetti, 1985; Keith et al., and Holland, 2007). In contrast, although not independent
1987; Oakland and Harrison, 2008; Alexander and Reynolds, of cultural and contextual expectations about development,
2020). For example, multiple studies of autism spectrum disorder adaptive behavior measures may be less susceptible to systematic
(ASD) show that adaptive behavior can be significantly impaired biases related to SES or race/ethnicity because of the focus on
even among individuals with high IQ (Klin et al., 2007; everyday functioning within his/her own environment of an
Duncan and Bishop, 2013; Kraper et al., 2017; Meyer et al., individual (Reschly et al., 2002a). However, given the limited
2018). Furthermore, among adults with neurodevelopmental research on adaptive behavior in general population samples,
disabilities, especially those with ASD without ID, it is adaptive much less is known about adaptive behavior correlates, or how
behavior (and not IQ) that is most associated with functional these correlates differ from those of IQ. This information is
outcomes (Farley et al., 2009; Woolf et al., 2010; Taylor and essential to inform choices of meaningful outcomes in children
Mailick, 2014; Taylor et al., 2015; Bishop-Fitzpatrick et al., 2016). from diverse backgrounds.
Information about the relationship between IQ and adaptive As mentioned above, the majority of research on adaptive
behavior in typically developing populations is more limited behavior has been conducted within clinical populations
and comes mainly from validation studies of adaptive behavior of children and adults with intellectual and developmental
measures showing that, as intended, IQ and adaptive behavior are disabilities (Ditterline et al., 2008). This study has focused mainly
only moderately correlated (Sparrow et al., 2005, 2016; Harrison on individual-level predictors of adaptive behavior and has
and Oakland, 2015). identified IQ, language, and executive functioning as significant
In young children, adaptive behavior measures consider a (Kanne et al., 2011; Ware et al., 2012; Bal et al., 2015; Pugliese
wide range of developmentally relevant constructs known to et al., 2015; Gardiner and Iarocci, 2018; Bertollo et al., 2020).
affect early childhood outcomes, such as executive functioning, Relatively few studies have examined how the aspects of the social
behavioral inhibition, social-emotional skills, and pre-academic environment are related to adaptive behavior skills (Glaser et al.,
skills (Luckasson et al., 2002; Sparrow et al., 2005; Oakland 2003). However, a handful of studies have shown that maternal
and Harrison, 2008). Thus, adaptive behavior may serve responsivity and growth facilitating behaviors (e.g., basic care and
as a proximal indication of how an individual functions learning activities) promote adaptive skills in very young children
within developmentally relevant contexts and provide additional (Altman and Mills, 1990) and children with developmental delays
information important for conceptualizing the profile of risk of (Fenning and Baker, 2012; Warren et al., 2017). These findings
an individual child and resilience in their specific environment suggest that understanding the influences of modifiable social
(Test et al., 2009; Bal et al., 2015; Dell’Armo and Tassé, 2019). environmental factors, including factors related to parent–child
In addition, adaptive behavior has been shown to be amenable interactions, could have important implications for interventions
to treatment in children with developmental disabilities (Matson designed to improve adaptive behavior.
et al., 2012; Bal et al., 2015; Duncan et al., 2018), making it a This study was conducted to examine the correlates of IQ
particularly appealing endpoint for targeted interventions. and adaptive behavior in a group of non-clinically referred
Intelligence quotient is commonly included as both a preschoolers from Flint, MI, USA. All children in this study
predictor and an outcome in epidemiological research on child were postnatally exposed to the Flint water crisis, which began
development (Halle et al., 2009; Calvin et al., 2017). Studies have in April 2014 and imposed unprecedented trauma on the Flint
shown that IQ is predictive of many important developmental community with lead exposure and increased stress related to
outcomes, including language ability and academic performance water use and beyond (Hanna-Attisha et al., 2015; Ruckart et al.,
(Neisser et al., 1996; Mayes et al., 2009; Duckworth et al., 2019). Thus, these children experienced myriad socioeconomic

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Zheng et al. IQ and Adaptive Behavior Correlates

and environmental exposures (e.g., racism, poverty, and lead) and Human Services and Hurley Medical Center approved the
during the first few years of life. Comprehensive assessments affiliated recruitment protocol. Informed consent was obtained
were conducted to assess the neurodevelopmental functioning from mothers and verbal assent was obtained from children
of children across multiple domains, with previous analyses by before the beginning of participation.
our group showing highly variable developmental profiles within
the sample at the age of 4 years (Zheng et al., 2021). Building Measures
on this work, we employed a data-driven approach to explore The two main child outcomes of interest for this study
associations between a broad range of social and environmental were measured with widely used standardized measures.
predictors and two main child outcomes of interests, namely, IQ IQ was measured using the Wechsler Preschool and
and adaptive behavior. This study was motivated by an interest in Primary Scale of Intelligence–Fourth Edition (WPPSI–IV),
identifying potentially modifiable correlates of IQ and adaptive a commonly used intelligence test designed for children
behavior, with a particular goal of understanding the utility of aged 2 years, between 6 months and 7 years, and 7 months
measuring adaptive behavior as an alternative outcome in high- (Wechsler, 2012). The current analysis used the norm-
risk samples like those of ours. referenced standard scores corresponding to full-scale IQ
(FSIQ) with a mean of 100 and an standard deviation (SD)
METHOD of 15.
The Vineland Adaptive Behavior Scales (Sparrow et al.,
Participants 2005, 2016; Vineland 3; Vineland-II) was used to measure the
Mother–child dyads were invited to participate if the child was adaptive behavior skills. Adaptive behavior measures, such as the
born between March 1, 2012 and April 24, 2014 (before the Vineland, involve clinical interviews or checklists completed by
water source change) and if the child resided in the City of informants who have regular opportunities to directly observe
Flint and received water from the Flint water distribution system adaptive behaviors performed within the everyday environment
between April 25, 2014 and October 15, 2015. Children who fit of an individual (Reschly et al., 2002b; Tassé et al., 2012; Harrison
these inclusion criteria would have been exposed to the water and Oakland, 2015). Given that this study focused on preschool-
within the first 2 years of life and were old enough to complete aged children who typically spend the majority of time with
direct assessments of developmental domains of interest at the primary caregivers, mothers served as the informant about the
in-person visit. adaptive behavior skills of children. Because of protocol changes
Families who expressed interest in participation were screened that occurred mid-study, some mothers completed the Vineland-
for eligibility. Children were excluded if they were wards of II comprehensive interview form (N = 40) and others completed
the state, if their birth weight was <1,500 g, if their gestational the Vineland-3 online parent-report form (N = 117). Both
age was <32 weeks, or if they had a known genetic syndrome. versions yield an adaptive behavior composite (ABC) score
Mother–child dyads were only included if the caregiver of the representing the overall level of adaptive functioning, which was
eligible child was their biological mother, spoke English, and used in the current analysis.
reside with and consistently care for the child. To ensure that they Social environmental exposures of interest were collected
could validly complete the tests included in the direct assessment from parents via interviews and questionnaires. These variables
battery, children were also excluded if they were currently non- were selected given demonstrated associations with child
verbal or had significant hearing or visual impairments. A total of neurodevelopmental outcomes and because they could be
390 mother–child dyads participated in screening, of whom 284 considered modifiable by programs, practices, or policies (the
dyads were determined to be eligible and 272 agreed to enroll. A detailed descriptions of each measure and example citations
total of 184 families attended an in-person assessment, of whom showing their associations with child outcomes are shown in
157 completed the Vineland Adaptive Behavior Scale and 174 Table 2).
completed the IQ test. The characteristics of the full sample are Maternal characteristics included depressive symptoms
shown in Table 1. measured by the Center for Epidemiological Studies Depression
Scale (Radloff, 1977), stress measured by the Perceived Stress
Procedure Scale (Cohen et al., 1983), potential problems with substance
Once eligibility was established, mothers completed online and use was measured by the CAGE Adapted to Include Drugs
in-person surveys, and children completed direct in-person screener (Brown and Rounds, 1995), and dispositional optimism
assessments. For mothers who expressed any difficulty with measured by the Life Orientation Test-Revised (Scheier et al.,
reading or seemed to struggle to understand the questions, 1994). Maternal perceived social support was measured by the
trained research staff were available to read the questions and Social Support Questionnaire (Sarason et al., 1983), and domestic
record their responses (on the phone or in person) to ensure the violence was measured using the 4-item HARK (Sohal et al.,
validity of their report and minimize barriers to participating. 2007).
All research assistants involved in the assessments received Parenting measures included the Child Rearing Practices
training and supervision in the administration of study measures Report (CRPR) nurturance and conflict subscales (Rickel
from a licensed clinical psychologist. The institutional review and Biasatti, 1982), the Knowledge of Effective Parenting
board at the institutions of authors reviewed and approved Scale (Winter et al., 2012), the Network of Relationship
the study protocol, and the Michigan Department of Health Inventory-Criticism Scale (revised parent version; Furman and

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Zheng et al. IQ and Adaptive Behavior Correlates

TABLE 1 | Demographic characteristics of the current sample (N = 184).

Variables Categories N %

Child gender Male 100 54.4%

Female 84 45.6%
Child race White 28 15.2%
Black or African American 125 67.9%
Other 3 1.6%
Multi-race 23 12.6%
Missing 5 2.7%
Child ethnicity Non-Hispanic 165 89.7%
Hispanic 19 10.3%
Maternal education level Less than high school 22 12.0%
High school or GED 67 36.4%
Vocational or technical school 5 2.7%
Some college or associate degree 69 37.5%
College graduate or bachelor’s degree 12 6.5%
Graduate degree 4 2.2%
Missing 5 2.7%
Maternal employment Employed and working 95 51.6%
Not employed 83 45.1%
Missing 6 3.3%
Household income level < $10,000 62 33.7%
$10,000–$15,000 34 18.5%
$15,001–$25,000 21 11.4%
$25,001–$35,000 16 8.7%
$35,001–$45,000 9 4.9%
More than $45,000a 17 9.2%
Don’t know 16 8.70%
Missing 9 4.89%
Number of children in the household 1 36 19.6%
2 47 25.5%
3 50 27.2%
≥4 41 22.3%
Missing 10 5.4%

N M (SD) Range

Child age 184 5.48(0.38) [4.05, 6.22]

Maternal age 184 31.46(6.32) [21.25, 52.95]

a Given
the small numbers in each of the below categories, we collapsed multiple categories into one: $45,001–$55,000, $55,001–$65,000, $65,001–$75,000, $75,001–$100,000,
$100,001–$150,000, $150,001–$200,000, $200,001, or more.

Buhrmester, 1985), and the stimulation questionnaire (StimQ- (including unemployed and retired). Since most of the mothers
Parent; Mendelson et al., 2016; Read Scale and Parent Verbal were either high school graduates or had completed some college
Responsivity Scale). education (Table 1), we coded maternal education level as high
Early childhood experiences were measured using the National school graduate and below vs. some college and above. Regarding
Survey of Children’s Health adverse childhood experiences household income, we adopted the Organization for Economic
questions (Bethell et al., 2017). Co-operation and Development (OECD)-modified equivalence
Sociodemographic characteristics, including highest maternal scale to adjust the income level based on the household sizes:
education, maternal relationship status, maternal employment first, the household size was determined by assigning a value of
status, and annual household income and household size, were 1 to the household head, 0.5 to each additional adult member,
collected through surveys completed by mothers. Specifically, and 0.3 to each child (Organisation for Economic Co-operation
maternal relationship status was coded as single vs. partnered/in Development, 2021); then, we took the medians of the income
a relationship, and maternal employment status was coded as categories (e.g., for category $15,001–$25,000, median $17,500
working (including full-time and part-time) vs. not working was used, $5,000 was used for the “<$10,000” category, and

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Zheng et al. IQ and Adaptive Behavior Correlates

TABLE 2 | Description of exposure measures included.

Measure Summary Variable entered in Example citations*

LASSO

Center for Epidemiological The CES-D consists of 20 self-report items assessing for depression. Standardized CES-D Murray et al., 1996; Barker
Studies-Depression Scale Each item is rated on a four-point scale from “Rarely or none of the summary score et al., 2011; Huang et al.,
(CES-D) Radloff (1977) time (<1 day)” to “Most or all of the time (5–7 days)” over the past 2014; Bush et al., 2020
week. Higher scores on the CES-D indicate higher levels of depressive
symptoms, with a cut-off of 16 denoting clinically significant depressive
symptoms Lewinsohn et al. (1997).
Perceived Stress Scale (PSS) The PSS includes ten items on a five-point scale form “Never” to “Very Standardized PSS total Weinraub and Wolf, 1983;
Cohen et al. (1983) often,” measuring perceived stress during the last month. Total scores score Keim et al., 2011; Huang
on PSS were calculated for analysis, with higher scores indicating et al., 2014; LeWinn et al.,
higher stress. 2020
The CAGE Adapted to Include The CAGE–AID is used to screen the respondent for problems Standardized CAGE-AID Blanchard et al., 2005
Drugs (CAGE-AID) Brown and associated with drug abuse. The assessment is self–completed and total score
Rounds (1995) consists of four yes/no questions. The participant is asked about
cutting down (or feeling they should cut back on drug use), annoyance
(whether others have been annoyed with the participant’s drug use),
feeling guilty (about drug use), and the use of “eye–openers” (feeling
the need to use drugs upon waking in the morning).
Life Orientation Test-Revised The Life Orientation test is used to assess the dispositional optimism Standardized LOT total Baker et al., 2005
(LOT-R) Scheier et al. (1994) (the general expectancy of positive outcomes) and psychological score
resilience of the respondent. It is a self–reported test containing 10
items. Three of these items are positively worded, three are negatively
worded, and the remaining four are fillers. Each item is rated on a
four–point scale (0 = strongly disagree, 1 = disagree, 2 = neutral,
3 = agree, and 4 = strongly agree). The negative items are reverse
scored, and the fillers are left unscored.
Social Support Questionnaire This questionnaire is used to measure the respondent’s perceived level Standardized SSQ support Weinraub and Wolf, 1983;
(SSQ) Sarason et al. (1983) of social support and to measure their satisfaction with this support. level score and satisfaction Burchinal et al., 1996;
For each item, the respondent must list all of those who fit the score Huang et al., 2014
description of the question, describe their relation to the person listed,
then rate how satisfied they are with these relationships on a six–point
scale (1 = very dissatisfied, 6 = very satisfied). The version adapted by
the study contains 6 items, asking the respondent who in their lives
they find dependable, helps them relax, accepts them fully, cares about
them, helps them feel better, and consoles them.
HARK 4 item Sohal et al. (2007) The HARK questions are used to identify victims of intimate partner Standardized HARK sum Harding et al., 2013; Vu
violence (IPV). HARK is an acronym for Humiliation, Afraid, Rape, Kick, total score et al., 2016
and each of the four items in the test pertains to one of these
categories (humiliation, intimidation, sexual assualt, and physical
abuse). The questions are in yes/no format and one point is given for
every “yes” answer. Studies show the test to accurately identify women
experiencing IPV.
Child Rearing Practices Report The CPRP evaluates the goals, values, and attitudes of parents in Standardized CRPR Farah et al., 2008; Rochelle
(CRPR): nurturance and conflict regards to raising a child. The Nurturance subscale of the test adapted Nurturance summary total and Cheng, 2016; Bush
subscale Rickel and Biasatti by the study specifically evaluates the respondent’s level of affection, score et al., 2020; LeWinn et al.,
(1982) attention, and nurturance that they provide to their child. This subscale Principal Component Score 2020
contains 18 items. The conflict subscale is used to assess the level of of the three conflict items
conflict between the respondent and their child. This subscale contains
3 items.
Both subscales are parent–completed and each question is rated on a
six–point scale (1 = Not at all descriptive of me, 6 = highly descriptive
of me). The CPRP is shown to reliably predict children’s future
adaptation Gerhardt et al. (2003)

(Continued)

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Zheng et al. IQ and Adaptive Behavior Correlates

TABLE 2 | Continued

Measure Summary Variable entered in Example citations*

LASSO

Knowledge of Effective Parenting The KEPS is used to measure the respondent’s knowledge of effective Standardized KEPS score Winter et al., 2012; Rochelle
Scale (KEPS) Winter et al. (2012) parenting strategies for parents of children aged 2–10. The test and Cheng, 2016
adapted by the study contains 17 items, all of which are
multiple–choice format. These items address four main areas of
parental knowledge: promotion of development, principles of effective
parenting, use of assertive discipline, and causes of behavior problems
Winter et al. (2012). One point is given to the respondent for each
question answered correctly. Previous studies have shown that the test
has good content validity, satisfactory test–retest reliability, and internal
consistency Winter et al. (2012).
Network of Relationship The adapted NRI is used to evaluate the frequency of criticism and Standardized NRI average Harris and Howard, 1984;
Inventory (NRI)—Criticism Scale harsh feedback that the respondent gives to their child. The survey is score across items Jacquez et al., 2004;
(revised parent version) Furman parent–completed and contains three items measured on a five–point Wolford et al., 2019
and Buhrmester (1985) scale (Little or none, Somewhat, Very much, Extremely much, The
most).
StimQ-Parent (StimQ-P) read This test evaluates cognitive stimulation in the home environment for Standardized StimQ-P total Rodriguez and
scale and parent verbal children aged 36–60 months. The questionnaire is parent–completed score Tamis-LeMonda, 2011;
responsivity scale Mendelson and consists of mostly “yes or no” questions. The StimQ—P2 contains Baker, 2013; Malhi et al.,
et al. (2016) four subscales: Availability of Learning Materials, Reading (“reflecting 2018; LeWinn et al., 2020
access to books, frequency of shared reading, variety of books read,
and interactivity/quality of reading”), Parental Involvement in
Developmental Advance, and Parental Verbal Responsivity. The version
adapted for the study solely includes questions regarding book reading
quantity, book reading quality, and parental responsivity (during
everyday routines, during play, and during activities that promote
regulation).
National Survey of Children’s This 8-item questionnaire assesses the health and well–being of Standardized total number Crouch et al., 2019
Health ACE questions Bethell children aged 0–17 based on the amount of reported Adverse of ACEs reported
et al. (2017) Childhood Experiences (ACEs). These questions assess whether the
child has witnessed and/or experienced parental divorce, death of a
parent, parental incarceration, domestic abuse, neighborhood violence,
household mental illness, household substance abuse, and racial
discrimination. Studies consistently show that an increasing number of
ACEs has a strong relationship with poorer health outcomes. However,
the ACE assessment is not recommended to be used as a diagnostic
tool, but to open dialogue and to indicate a need for further evaluation
Bethell et al. (2017).
Demographics survey The purpose of this questionnaire is to gather information about the Maternal education level Duncan et al., 1994; Noble
background and living arrangements of the respondent and their child. Maternal relationship status et al., 2005; Bush et al.,
Specifically, the child’s and mother’s age, sex, and race. The survey Maternal employment status 2020; LeWinn et al., 2020
then addresses information specifically regarding the parent’s Household income level
background, such as educational history, employment status, and Number of children in
marriage status, household income levels, and number of children in the household
the household.

* Previous studies showing associations of the measured construct/exposure with child outcomes.

$200,000 used for “$200,000 and more”) to be divided by the analysis, summary scores of the measures were used. When
household sizes to generate the OECD-modified income level; a summary score was not available (i.e., the child-rearing
finally, the number of children in the household was included as practices–conflict subscale), the principal component analysis
a categorical variable with four classes, namely, 1, 2, 3, and ≥4. was conducted to generate a single score to be included in the
A priori identified confounders included child age, child sex at regression models.
birth, and maternal age.
Predictor Selection
Analysis Plan We applied the least absolute shrinkage and selection operator
Descriptive statistics (i.e., mean and SD) for the primary child (LASSO) method to select predictors from the full list of
outcomes, predictors, and confounding variables of interest target exposures (N = 18) to be included in the regression
were generated (see Table 1 for demographic variables and models predicting adaptive behavior skills and IQ levels (see
Supplementary Table 1 for descriptive statistics on maternal Table 2 for variables entered in LASSO regression). The LASSO
characteristics and parenting measures). For the regression method offers the advantage of selecting stable predictors and

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Zheng et al. IQ and Adaptive Behavior Correlates

excluding factors with nominal effects and collinear covariates. Predictors of IQ

All continuous variables were standardized with a mean of 0 and The LASSO regression consistently selected the maternal
an SD of 1 to be on the same scale of influence on the penalty education level as a predictor of child IQ across all models
term in the LASSO model. In this analysis, we applied 5-fold (Table 3). The other predictor identified by two out of four
external cross-validation for determining the LASSO model with models was OECD-adjusted household income. When the
model selection based on the fit indicator of predicted residual maternal education level, together with a priori predictors (i.e.,
sum of square (PRESS) for k-fold external cross-validation. child sex, child age, and maternal age), were included in the
Furthermore, due to concerns of overfitting with a relatively small same model, the maternal education level (β = 0.48, 95% CL:
sample and to achieve higher confidence for predictor selection, 0.19–0.77) and child sex (β = 0.47, 95% CL: 0.18–0.76) were
we conducted LASSO modeling with different partitioning with significant (Table 4). Maternal education and child sex remained
a random selection of training and testing samples from the full the significant predictors of IQ when OECD-adjusted income
sample to examine the resulting model as follows: (1) LASSO was added to this model (1R2 = 0.019; Table 4). Children with
models run with the full sample used for training, (2) LASSO mothers who had received more than high school education
models run in 90% of the sample for training and 10% for testing, showed IQ scores with an SD of 0.40 higher than those with
(3) LASSO models run in 80% of the sample for training and mothers with lower educational levels, and girls received IQ
20% for testing, and (4) LASSO models run in 70% of the sample scores with an SD of 0.45 higher than boys. The estimated
for training and 30% for testing. LASSO selection results from coefficient of OECD-adjusted income level was not significant.
each model were presented and compared with fit indices of the
Akaike Information Criterion, PRESS, and average squared error Predictors of Adaptive Behavior
of the training and testing samples. Separate LASSO regressions Least absolute shrinkage and selection operator regression
were run to select the sets of reliable predictors of adaptive models with adaptive behavior as the outcome consistently
behavior and IQ. selected the child-rearing practice–nurturance subscale score and
social support satisfaction across three LASSO models, with
the maternal report of home stimulating level selected by only
Post-LASSO Regression Models one model (Table 3). Nurturance and social support satisfaction
In the post-LASSO analysis, the multiple linear regressions scores were entered in a regression model with adaptive behavior
with standardized scores were fitted to estimate the magnitude as the outcome along with the a priori confounders (i.e., child age,
of coefficients associated with predictors of adaptive behaviors child biological sex, and maternal age). Child-rearing nurturance
and IQ separately while controlling for a priori identified showed a significant association with adaptive behavior, along
confounders. Predictor(s) that were consistently selected across with child and maternal age (Table 5). Specifically, when mothers
LASSO models for either adaptive behaviors or IQ were entered scored an SD of 1 higher on the nurturance scale, children
into respective linear models first, and then the other predictors showed an SD of 0.25 (95% CL: 0.07–0.42) increase in adaptive
selected inconsistently by LASSO models were entered at a later behaviors. In contrast, child and maternal age were negatively
step. Coefficients of LASSO-selected predictors were estimated associated with adaptive behavior scores as follows: child age
adjusting for confounders identified a priori (i.e., child age, child β = −0.23 (95% CL: −0.39 to −0.07) and maternal age β =
sex at birth, and maternal age). For adaptive behavior and IQ −0.21 (95% CL: −0.38 to −0.04). When adding the home
models, we reported the standardized parameter estimates (β) stimulating level to the regression model, nurturance (β = 0.25,
with 95% confidence limits (CL), effect sizes (partial η2 ), and p- 95% CL: 0.07–0.44) and child age (β = −0.26, 95% CL: −0.41 to
values for all the predictor variables and possible confounders at −0.10) remained significant at a similar magnitude of effect.
each step, and R2 and R2 changes of the models.
DISCUSSION
This study explored the utility of measuring adaptive behavior,
RESULTS in addition to IQ, in studies of children at heightened risk
for neurodevelopmental problems. Using the data from
Flint preschoolers in the current sample showed a wide range of comprehensive assessments of preschoolers exposed to the
adaptive behavior and IQ scores, with the mean level of adaptive Flint water crisis, we found that 71% of children demonstrated
behaviors falling within the adequate range based on the norm- adaptive behavior skills at or above age level on the Vineland
referenced ABC score (M = 94.67, SD = 15.73, IQR = 19, range: Adaptive Behavior Scales, while only 55% of children had
48–140) and the mean FSIQ falling in the low average range (M measured IQ in the average or above range on the WPPSI-IV.
= 88.07, SD = 12.48, IQR = 20, range = 62–120). Vineland ABC These findings demonstrate the potential value of measuring
scores and WPPSI FSIQ scores showed only a small correlation adaptive behavior to capture additional capabilities not
of 0.27. Measures of social-environmental characteristics (e.g., necessarily reflected by IQ scores. Furthermore, our analyses
maternal mental health and parenting) showed a wide range identified different socio-demographic correlates of adaptive
of scores, spanning the full range for most of the measures. behavior as compared with IQ, with implications for measuring
The descriptive statistics and correlation matrix are shown in developmental outcomes and targeting modifiable factors to
(Supplementary Tables 1, 2). improve these outcomes.

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Zheng et al. IQ and Adaptive Behavior Correlates

TABLE 3 | Results from LASSO models with adaptive behavior and IQ as outcomes with different sample partitioning.

LASSO-selected AIC Press ASE for ASE for

predictors training testing
sample sample

IQ LASSO results Full sample training Maternal education 78.765 0.943 – –

90% for training vs. Maternal education, 77.074 0.987 1.001 0.279
10% for testing Income per capita
80% for training vs. Maternal education 68.545 0.944 1.026 0.882
20% for testing
70% for training vs. Maternal education, 57.221 1.062 0.915 1.089
30% for testing Income per capita
Adaptive behavior Full sample training CRPR nurturance, 72.164 0.874 – –
LASSO results social support
satisfaction
90% for training vs. CRPR nurturance, 69.337 1.002 0.884 0.695
10% for testing social support
satisfaction
80% for training vs. CRPR nurturance, 54.330 0.807 0.752 1.062
20% for testing social support
satisfaction, Stimulating
environment
70% for training vs. Intercept only 56.966 1.029 0.981 1.003
30% for testing

AIC, Akaike information criterion; PRESS, predicted residual sum of square; ASE, average squared error.

TABLE 4 | Results from adjusted model of LASSO-selected predictors for IQ with standardized scores.

Model 1 (N = 174) Model 2 (N = 142)

R-Square: 0.122 p = 0.0002 R-Square: 0.141 p < 0.0001

β (95% CI) p Partial η2 β (95% CI) p Partial η2

LASSO selected Maternal education ≤High school [Reference] – – [Reference] – –

>High school 0.48 (0.19, 0.77) 0.001 0.06 0.40 (0.07, 0.72) 0.017 0.04
Household income 0.15 (−0.00, 0.31) 0.062 0.02
A priori confounders Child sex Male [Reference] – – [Reference] – –
Female 0.47 (0.18, 0.76) 0.001 0.06 0.45 (0.13, 0.77) 0.006 0.05
Child age 0.02 (−0.13, 0.17) 0.818 0.00 0.00 (−0.16, 0.17) 0.973 0.00
Maternal age 0.03 (−0.11, 0.18) 0.680 0.00 0.04 (−0.12, 0.20) 0.648 0.00

With regard to predictors of adaptive behavior, scores on the contrast, other LASSO-selected predictors (i.e., social support
CRPR nurturance subscale, which is designed to capture positive satisfaction and stimulating home environment) did not show
parenting strategies and parent–child relationships (Rickel and significant associations with adaptive behavior scores in the
Biasatti, 1982), emerged as a significant positive predictor with linear regressions. Taken together, these findings suggest that
a medium effect size after accounting for a priori confounders. (1) positive mother–child relationships and interactions matter
This is consistent with previous findings showing that parenting for the development of adaptive behaviors of children, and
styles and behaviors impact the adaptive behavior of children (2) mothers with less satisfying social support or limited
(Altman and Mills, 1990; Rinaldi and Howe, 2012). Previous resources and skills could still foster adequate adaptive skills in
studies of young children suggest that caregivers with higher their children.
responsivity are more likely to develop positive relationships Different from the predictors of adaptive behavior, the
with their children and to facilitate gains in adaptive behaviors predictors identified by the LASSO regression for IQ included
within a nurturing environment (Bradley et al., 1995; Glaser maternal education and household income level, with maternal
et al., 2003; Fenning and Baker, 2012; Warren et al., 2017). In education level showing a significant association in the linear

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Zheng et al. IQ and Adaptive Behavior Correlates

TABLE 5 | Results from the adjusted model of LASSO-selected predictors for adaptive behavior with standardized scores.

Model 1 (N = 137) Model 2 (N = 115)

R-Square: 0.178 p < 0.0001 R-Square: 0.206 p = 0.0003

β (95% CI) p Partial η2 β (95% CI) p Partial η2

LASSO selected CRPR nurturance 0.25 (0.07, 0.42) 0.007 0.05 0.25 (0.07, 0.44) 0.008 0.06
SSQ satisfaction 0.07 (−0.10, 0.24) 0.443 0.00 0.09 (−0.09, 0.27) 0.307 0.01
Stimulating environment 0.10 (−0.07, 0.27) 0.254 0.01
A priori confounders Child sex Male [Reference] – – [Reference] – –
Female 0.27 (−0.05, 0.59) 0.103 0.02 0.24 (−0.10, 0.58) 0.160 0.02
Child age –0.23 (–0.39, –0.07) 0.004 0.06 –0.26 (–0.41, –0.10) 0.002 0.09
Maternal age –0.21 (0.38, –0.04) 0.015 0.04 −0.11 (−0.30, 0.07) 0.220 0.01

regression. This is consistent with previous studies showing that associated with adaptive behavior scores, suggesting that children
maternal education levels are a core factor in predicting child may fall further behind the pace of the normative sample due to
cognitive development (Harding et al., 2015; Jackson et al., 2017; a cumulative effect of environmental disadvantages (Garcia Coll
Reardon, 2018). While income levels and maternal education et al., 1998; Darbeda et al., 2018). The longitudinal data will be
are often correlated (in the current sample, mothers with more required to determine whether the relative strength in adaptive
than high school education had higher household incomes, t = behavior for this sample persists as they grow into school age
−2.79, p < 0.01), both are commonly found to be independently and beyond.
associated with child cognitive development (Tong et al., 2007; There are several limitations to be considered when
Hackman and Farah, 2009; Patra et al., 2016). The effect of interpreting the current findings. The sample size was relatively
SES on child intelligence has been attributed to better access small, and all children were exposed to the Flint water crisis
to a stimulating and resourceful learning environment (e.g., and multiple socioeconomic adversities. Therefore, replication
books, toys, and learning activities) (Duncan and Brooks-Gunn, in other samples is needed to determine the generalizability
2000; Tong et al., 2007; Christensen et al., 2014). It is likely of these results. Our small sample size may also have resulted
mothers with higher educational levels are better equipped to in limited power with which to detect statistically meaningful
provide an environment for promoting cognitive development effects in the regression models. That is, candidate exposures
(Dichtelmiller et al., 1992; Benasich and Brooks-Gunn, 1996; that were not selected by the LASSO or were not significant
Winter et al., 2012). in the linear regression should be interpreted with caution
The emergence of nurturance as a significant predictor of and not discounted in future research of IQ and adaptive
adaptive behavior suggests that interventions could potentially behaviors. Moreover, given that the variances explained in the
target nurturing practices among parents to improve the adaptive adaptive behavior and IQ models were small (R2 : 0.12–0.21),
functioning of children (O’Connell et al., 2015; Roby et al., more studies with longitudinal data and larger samples are
2021). In fact, programs such as Reach Out and Read and the needed to corroborate and extend our understanding of how
Video Interaction Project (Cates et al., 2016; Weisleder et al., adaptive behaviors and IQ change as a result of modifiable
2019; Canfield et al., 2020) have been put in place to provide social environmental variables. Additionally, with the goal of
Flint parents with resources and training to promote positive reducing the burden of participants, we implemented a protocol
parenting practices. Possible targets for improving the cognitive change during the study resulting in the use of different
performance are less clear since SES factors are often a result versions of the Vineland scales with different data collection
of societal and structural challenges, and substantial long-term modalities (Vineland-II comprehensive interview vs. Vineland-
investment and intervention are often needed to bridge the 3 parent-report survey). Although the ABC scores of high
cognitive performance gaps (Currie and Thomas, 1993; Campbell concurrent validity between Vineland-II and Vineland-3 has
et al., 2002; Anderson et al., 2003; Love et al., 2005; Dobbie and been reported (Sparrow et al., 2016), and we observed similar
Fryer, 2011). ABC score distributions (Supplementary Figure 1) and patterns
We also observed associations between IQ and adaptive (Supplementary Table 3) on the two versions in this study, the
behavior and child sex and child age. Our findings on the use of different forms to measure adaptive behavior is still
advantage of females in IQ among Flint children are consistent a limitation. Another limitation is that our models included
with previous findings showing that males are at greater risk only binary maternal education levels. It is possible that more
for neurodevelopmental disorders (Boyle et al., 2011) and more nuanced effects of maternal education levels could be detected
susceptible to environmental exposures (Jedrychowski et al., if more levels of maternal education were considered in a
2009; Chiu et al., 2017; DiPietro and Voegtline, 2017; Torres- larger sample. However, this study was the first to employ
Rojas and Jones, 2018). In addition, child age was negatively LASSO regression to select and then examine the correlates

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Zheng et al. IQ and Adaptive Behavior Correlates

of adaptive behaviors in comparison to IQ. Our findings and KL led the data collection. All authors contributed to the
underscore the value of measuring adaptive behaviors in addition article and approved the submitted version.
to IQ in studies of young children at heightened risk for
neurodevelopmental difficulties.
FUNDING
DATA AVAILABILITY STATEMENT This study was supported by the Robert Wood Johnson
Foundation (Grant Nos. 74129 and 77131) and Metabolic Studio,
The raw data supporting the conclusions of this article will be the direct charitable activity of the Annenberg Foundation (Grant
made available by the authors, without undue reservation. No. 18-414) to Michigan State University.

ETHICS STATEMENT
ACKNOWLEDGMENTS
The studies involving human participants were reviewed and
approved by Michigan State University, University of California, We are thankful to Adam Flood, Katlin Harwood-Schelb,
San Francisco. Written informed consent to participate in this Christopher Valvano, and Quiana Wheeler for their research
study was provided by the participants’ legal guardian/next of kin. assistance for the project. We would also like to thank all the
families who generously participated in this study and supported
our research effort.
AUTHOR CONTRIBUTIONS
SZ, SB, and KL conceptualized the study. SZ conducted the SUPPLEMENTARY MATERIAL
statistical analysis. SZ and SB drafted the original manuscript.
SB and KL provided major revisions to the drafts. TC, MH-A, The Supplementary Material for this article can be found
and LO’C provided feedbacks and edits to the final manuscript. online at: https://www.frontiersin.org/articles/10.3389/fpsyg.
MH-A and KL secured the funding for the study. TC, SB, MH-A, 2021.692330/full#supplementary-material

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