Social Communication Is Predicted by Inhibitory Ability and ADHD Traits in Preschool-Aged Children

Abstract

Objective: Given the role inhibitory control plays in both ADHD and communication, this study examined whether inattentive and hyperactive-impulsive traits mediate the impact of weak inhibitory ability upon the knowledge and application of pragmatic rules early in development. Method: Participants were 36 typically developing preschoolers and their caregivers. ADHD traits were assessed per caregiver report. Inhibition was assessed in children using a distraction task. Pragmatic language was assessed by asking children about hypothetical social situations (knowledge) and by asking caregivers to report on children’s actual communicative behaviors (application). Results: Individual differences in inhibition predicted both facets of pragmatic language development. Hyperactive-impulsive behaviors were a significant mediator of this relationship—but only with regard to children’s ability to effectively apply pragmatic rules in everyday life. Conclusion: Our findings suggest that social communication difficulties in some young children are a downstream consequence of hyperactive-impulsive behaviors that arise from poorly developed inhibitory control.

Keywords

communication response inhibition ADD/ADHD preschoolers SWAN

ADHD is a common disorder of development that affects approximately 5% of school-aged children (Polanczyk, de Lima, Horta, Biederman, & Rohde, 2007). Characterized by developmentally atypical levels of inattention and hyperactivity-impulsivity, ADHD presents early in development and causes impairment across settings (American Psychiatric Association [APA], 2000). Prior to the age of 6, diagnosis of ADHD is complicated by the fact that the overt manifestations of the disorder are normative in typically developing preschool-aged children and tend to be transient in this age group (see Connor, 2002, for a review). Nonetheless, research has demonstrated that preschoolers show individual variability in the expression of ADHD traits (e.g., Lahey et al., 2004; Lakes, Swanson, & Riggs, 2012) and that these traits are more temporally stable and impairing in preschoolers who have a more severe symptomatic presentation—even if they do not meet full diagnostic criteria for the disorder (Lahey et al., 2004; Pierce, Ewing, & Campbell, 1999).

Efforts at elucidating the prevalence of ADHD traits in preschoolers have been accompanied by a growing interest in identifying correlates of the disorder that may emerge early in development (Cunningham & Boyle, 2002; DuPaul, McGoey, Eckert, & VanBrakle, 2001; Wilens et al., 2002). In addition to the core traits of inattention and hyperactivity-impulsivity that define ADHD, the broader disorder phenotype includes deficits in other areas of functioning, including social and emotional development, motor coordination, and executive control (see Tarver, Daley, & Sayal, 2014, for a review). The latter has been the focus of considerable empirical study within the context of ADHD (e.g., Seidman, 2006). One robust finding to emerge from this burgeoning literature is that response inhibition—defined as the ability to withhold highly prepotent but inappropriate behaviors (Nigg, 2000)—is strongly and consistently associated with the disorder. Not only are inhibitory deficits commonly experienced by children who have an ADHD diagnosis (e.g., Lipszyc & Schachar, 2010), but they are also prevalent among children with high levels of ADHD traits who do not meet full diagnostic criteria for the disorder, including young, preschool-aged children (Berlin & Bohlin, 2002; Sonuga-Barke, Dalen, Daley, & Remington, 2002; Thorell & Wåhlstedt, 2006). Although inhibitory deficits have thus traditionally been viewed as part of the broader disorder phenotype (Barkley, 1997), more recent theoretical accounts of ADHD have attempted to elucidate the precise nature of this relationship—questioning, for example, whether inhibitory deficits simply co-occur with ADHD or are causally implicated in the disorder. Consistent with the latter view, research has shown that inhibitory deficits are related to the proposed neurobiological underpinnings of ADHD (Aron & Poldrack, 2005), aggregate within families of ADHD probands (Crosbie & Schachar, 2001; Schachar et al., 2005), and persist irrespective of changes in disorder severity—being evident, for example, even in ADHD children who appear to “outgrow” their symptoms and impairment (McAuley, Crosbie, Charach, & Schachar, 2014). This growing empirical basis is consistent with the view that inhibition is an endophenotype of ADHD that holds an intermediate position in the causal pathway linking susceptibility genes to the overt manifestations of the disorder (Crosbie, Pérusse, Barr, & Schachar, 2008).

Social communication—or pragmatic language—is another domain that has been implicated in ADHD (Camarata & Gibson, 1999; Green, Johnson, & Bretherton, 2014). In contrast to inhibition, it has been suggested that pragmatic language deficits reflect downstream effects of the disorder that arise from underlying difficulties in inhibitory ability and other aspects of executive control (Bignell & Cain, 2007; Green et al., 2014; Nilsen & Fecica, 2011; Purvis & Tannock, 1997; Tannock & Schachar, 1996). Some of the pragmatic behaviors that have been associated with ADHD are embodied in diagnostic criteria for the disorder, such as difficulty attending when spoken to directly, interrupting others, and excessive talking (APA, 2000; Camarata & Gibson, 1999; Tannock & Schachar, 1996). Other pragmatic behaviors are not part of the diagnostic criteria per se but are commonly observed in school-aged children who have an ADHD diagnosis or who exhibit relatively high levels of ADHD traits. These findings are evident across both parent-report and performance-based tasks in which samples of the children’s communicative behavior are measured. Examples include generating verbal output that contains more ambiguous sentences, less informative content, and that is poorly organized overall (Purvis & Tannock, 1997; Tannock, Purvis, & Schachar, 1993); making less use of context when interpreting figurative language (Bignell & Cain, 2007); having difficulty adapting to changing roles during communicative exchanges (e.g., between the roles of speaker and listener; Kim & Kaiser, 2000; Landau & Milich, 1988; Whalen, Henker, Collins, McAuliffe, & Vaux, 1979); making more errors when interpreting instructions provided by others (Nilsen, Mangal, & MacDonald, 2013); and exhibiting higher rates of inappropriate conversational behaviors—such as starting conversations inappropriately, using stereotyped language (e.g., changing topics suddenly, directing conversation toward personal interests), and engaging in less rapport building (e.g., failing to respond to questions or requests; Bishop & Baird, 2001; Kim & Kaiser, 2000). These behaviors have been observed even when ADHD children possess age-appropriate knowledge of pragmatic rules (Kim & Kaiser, 2000), which suggests that the social communication difficulties evidenced by children who have an ADHD diagnosis, or who exhibit relatively high levels of ADHD traits, may not be solely attributable to a pragmatic knowledge deficit but rather may reflect difficulty with the application of existing knowledge in communicative contexts. Although comparatively little research has examined putative associations between pragmatic language and ADHD early in development, pragmatic language competence has been associated with inattention and hyperactivity in typically developing preschoolers (Ketelaars, Cuperus, Jansonius, & Verhoeven, 2010), and with symptoms of impulsivity more specifically in young children with ADHD diagnoses (Geurts & Embrechts, 2008).

In summary, ADHD is associated with difficulties in several areas—including inhibitory ability and pragmatic language, which have been conceptualized as possible causes and consequences of the disorder, respectively. Given the role that pragmatic language deficits are presumed to play in the social impairment that often accompanies ADHD (Leonard, Milich, & Lorch, 2011), an important goal for research is to further elucidate the underpinnings of pragmatic language difficulties that are experienced by children who either have ADHD or evidence high levels of ADHD symptoms. To this end, we selected inhibitory ability for inclusion in our study because we believe it may be one of several mechanisms that underlie the inattentive and hyperactive-impulsive traits that define ADHD and associated difficulties in pragmatic language skill. Because research has primarily been conducted with school-aged children who have received an ADHD diagnosis, however, the extent that these constructs show evidence of mediation early in normative development is unknown. As such, this study was undertaken to examine whether ADHD traits mediate the association of inhibitory ability and pragmatic language in typically developing preschool-aged children. We focused our study on typically developing preschoolers for several reasons: Preschool-aged children show large individual differences in ADHD traits, which are manifest and normative early in development (Lakes et al., 2012; Palfrey, Levine, Walker, & Sullivan, 1985); young children are less likely to have co-morbid conditions that may compromise the development of their social communication skills (Bignell & Cain, 2007); inhibition and pragmatic language undergo rapid changes during the preschool period (McAuley, Christ, & White, 2011; O’Neill, 2007); and focusing on typical development enables us to extend findings that have largely been derived from clinical samples to the general population. Consistent with current thinking regarding the causes and consequences of ADHD (e.g., Crosbie et al., 2008; Green et al., 2014), we hypothesized that inattentive and hyperactive-impulsive traits would mediate the relationship between inhibitory ability and pragmatic language. Based on the suggestion that social communication difficulties in ADHD children may reflect a dissociation between the application and acquisition of pragmatic knowledge (Kim & Kaiser, 2000), we further hypothesized that mediation would occur when children were required to demonstrate the appropriate use of pragmatic rules rather than their familiarity with these rules per se.

Method

Participants

Fifty-three children aged 36 to 47 months were recruited from a university-affiliated early childhood education center and from a database of community participants in the Department of Psychology at the University of Waterloo. Parents provided information regarding their children’s general health, developmental history, and language in a brief questionnaire developed by the investigators. Following recruitment, all children were invited to participate in a set of tasks during an individual testing session with the researcher. Children’s expressive and receptive language was screened using Body Part Naming and Identification from A Developmental Neuropsychological Assessment (NEPSY-II; Korkman, Kirk, & Kemp, 2007). Five children declined to participate in the individual testing session, and an additional four children declined to complete two or more of the tasks, and thus were not included in our analyses. An additional eight children were excluded from the study based on (a) suspected or diagnosed speech, hearing, or major health difficulties that would affect participation in the study; (b) less than 1-year exposure to English or minimal exposure to English on a daily basis; or (c) low performance (i.e., <10th percentile) on the language screening measure. The resulting sample (n = 36) consisted of 20 females (55.6%) and 16 males (44.4%), who ranged in age from 36 to 50 months (M = 43.12, SD = 3.69) at the time of testing. None of the children had diagnosed or suspected attention or behavioral concerns per parent-report. In all, 33 of the 36 children (91.7%) spoke English as their first language and 20 (55.6%) were not exposed to any additional languages. Most participants were Caucasian, reflecting the composition of our surrounding community, and came from families in which parents generally reported having a college or university degree, which is somewhat higher than our community average based on available census data (Statistics Canada, 2014).

Materials

Strengths and Weaknesses of ADHD-Symptoms and Normal-Behavior (SWAN) rating scale

The SWAN rating scale (Swanson, n.d.) is a parent or teacher questionnaire of traits associated with ADHD. Inattentive and hyperactive-impulsive dimensions are each represented by nine items reflecting diagnostic criteria outlined in the Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.; DSM-IV-TR; APA, 2000). For each item, children are scored on a 7-point scale ranging from far below average (+3) to far above average (−3), such that ratings of far below average indicate higher levels of inattentive and hyperactive-impulsive behavior relative to their same age peers. Total scores reflecting inattention and hyperactivity-impulsivity were the focus of our study (possible range = +27 to −27). Cronbach’s α for these subscales are .91 and .93, respectively (Lakes et al., 2012).

Statue

The Statue subscale of the NEPSY-II assesses motor persistence and inhibitory control in children aged 3 to 6 years (Korkman et al., 2007). In this task, children are asked to maintain a still and silent position (i.e., like a statue holding a flag with their eyes closed) despite a number of distractions being purposefully introduced by the researcher during a 75-s period (e.g., knocking on the table). Successful completion of this task requires the child to inhibit impulsive responding to the distractors. The number of errors reflecting bodily movements, eye openings, and vocalizations was examined in our study (possible range = 0-15). Test–retest reliability estimates are .82 for 3- and 4-year-old children from the normative sample (Korkman et al., 2007).

Pragmatic judgment

Pragmatic rule knowledge was assessed using the Pragmatic Judgment subtest of the Comprehensive Assessment of Spoken Language (CASL; Carrow-Woolfolk, 1999). This task, appropriate for use with 3- to 21-year-olds, consists of 60 orally administered and increasingly difficult items which require children to formulate and provide appropriate pragmatic responses to a variety of hypothetical social scenarios (e.g., being polite in conversation, seeking and providing accurate information, appropriately commenting on upsetting situations). Responses generally receive a score of 0 (incorrect) or 1 (correct) based on their pragmatic appropriateness, irrespective of the grammar or structure of the response. Administration began with the first item and was discontinued after 5 consecutive incorrect answers. The total number of points achieved across the administered items was examined in our study (possible range = 0-68, but note that preschool-aged children would meet the discontinue criterion well before this upper limit). Rasch split-half reliability is .79 for 3-year-olds from the normative sample (Carrow-Woolfolk, 1999).

Language Use Inventory (LUI) for young children

Pragmatic rule application was assessed using the LUI (O’Neill, 2009). The LUI is a parent questionnaire that measures how children 18 to 47 months use their language in everyday situations or during communicative acts with others (i.e., pragmatic language). The questionnaire contains 180 items, most in a “yes/no” format, which make up 14 subscales. Part 3 of the measure consists of nine subscales assessing children’s use of longer sentences in social communication (e.g., adapting conversations to the needs of others, telling coherent narratives, asking questions and making comments about themselves and others, using language to regulate others’ activities). Total raw scores on Part 3 were the focus of our study (possible range = 0-133). Parts 1 and 2 were not included because children in our age range either no longer show the behaviors that are assessed by these questions or perform at ceiling (O’Neill, 2007). Cronbach’s α for Part 3 is .99 for the normative sample (O’Neill, 2009).

Procedure

Parents of children recruited through the early childhood education center were given envelopes containing information about the study, consent forms, parent-filled questionnaires, and a $5 gift card. Parents of children recruited through the community database were contacted via telephone or email and completed the required forms during their visit to the self-contained, child-friendly testing room at the university. Once parental consent was obtained, children were invited to participate in the individual testing session and were informed that they could decline to participate or cease participating at any time. Sessions were approximately 20 min in length. Parents who wished to be present were given the option of observing through a one-way window or sitting quietly in a discrete area of the room where the research was taking place. Parents were reminded of the importance of not prompting their children during the tasks, and were asked to withhold feedback until the end of the testing. Tasks were administered according to the directions outlined in their respective administration manuals and were presented to children in the following order: Body Part Naming and Identification, Statue, Pragmatic Judgment. All testing was conducted by a graduate student experienced in working with young children who was blind to responses on the parent-completed questionnaires. At the end of the session, children were presented with certificates of participation and a small gift (e.g., stickers).

Results

Complete data were available for 32 participants (4 children declined to participate in the Statue task). Available data for all 36 participants were used to derive path values for the direct and indirect effects. The more conservative significance test for the indirect effect was then obtained from the data set comprised of the 32 participants for whom complete data were available. Descriptive statistics for variables that were entered into the analyses, and their correlations with age and gender, are presented in Table 1. Of note, there were no statistical outliers on any of the measures (i.e., scores outside 3 standard deviations of the sample mean), and almost none of the children had scores that would be considered “at risk” per recommended clinical cutoffs (e.g., Swanson et al., 2012) or comparisons with the normative sample (i.e., percentile scores below the 10th percentile). As shown in Table 1, gender was not significantly associated with any of the measures (ps > .10); however, age was negatively associated with body movement errors (r = −.40, p < .05) and positively associated with pragmatic language scores on the LUI and CASL (rs = .47 and .46, ps < .01, respectively). As such, children’s age at the time of testing was controlled in the mediation models. As per the recommendations of Hayes and Scharkow (2013), bias-corrected bootstrap tests of mediation were conducted using AMOS graphics software Version 21.0 (Arbuckle, 2012). This approach provides a more powerful test of indirect effects compared with other approaches in small samples (see also Woody, 2011). The models tested whether ADHD traits mediated the relationship between body movement errors from the Statue subtest of the NEPSY-II and pragmatic language. Body movement errors were selected as our index of inhibitory ability because of the infrequent occurrence of either eye opening or vocalization errors by participants.¹

Table 1.

Means, Standard Deviations, and Correlations With Age and Sex of Participants for Measures of ADHD Traits, Inhibitory Control, and Pragmatic Language.

Measure	M	SD	r _age	rpb _sex
ADHD traits
Inattention	−6.03	4.97	−.11	.25
Hyperactivity-impulsivity	−4.08	6.00	−.24	.08
Inhibitory control
Body movements	6.13	3.87	−.40*	.05
Eye openings	3.28	3.65	−.06	−.09
Vocalizations	0.94	2.06	−.19	−.25
Pragmatic language
LUI Part 3	123.14	7.20	.47**	.01
CASL	11.00	4.77	.46**	−.07

Note. Total raw score taken as an index of performance on all tasks. Inattention = score on items measuring inattentive symptoms (SWAN rating scale); hyperactivity-impulsivity = score on items measuring hyperactive-impulsive symptoms (SWAN rating scale); body movements = total number of body movement errors (statue); eye openings = total number of eye openings made (statue); vocalizations = total number of vocalizations made (statue); LUI = score on Language Use Inventory–Part 3; CASL = score on Comprehensive Assessment of Spoken Language Pragmatic Judgment subscale; SWAN = Strengths and Weaknesses of ADHD-Symptoms and Normal-Behavior.

p < .05. **p < .01.

Associations between inhibitory ability, inattention, and pragmatic language are depicted in Figure 1, with separate models presented for each pragmatic language outcome. There was a significant negative direct effect of inhibition on the CASL, such that children who made more body movement errors also demonstrated worse pragmatic judgment. In addition, there was a significant negative direct effect of inattention on the LUI, such that children who were rated as more inattentive were also described as engaging in less appropriate pragmatic behaviors by their parents. There were no other significant direct effects in either model (ps > .10). Furthermore, in neither model was the indirect effect of inhibition on pragmatic language significant (ps > .10).

Figure 1.

The mediational role of symptoms of inattention.

Associations between inhibitory ability, hyperactivity-impulsivity, and pragmatic language are depicted in Figure 2. In both models, there was a significant positive direct effect of inhibition on hyperactivity-impulsivity, such that children who made more body movement errors were reported to be more hyperactive and impulsive by their parents. In addition, as previously reported, there was a significant negative direct effect of inhibition on the CASL. In contrast to the models above, there was a significant indirect effect of inhibition on pragmatic language depending on the outcome measure that was examined. More specifically, although there was no direct effect of inhibition on the LUI, there was a statistically significant indirect effect that was mediated by hyperactivity-impulsivity (standardized indirect effect = −.15, p < .05). There was no evidence of mediation with respect to the CASL (standardized indirect effect = .06, p > .10). These results show that children who made more body movement errors were rated as more hyperactive and impulsive by their parents and these children, in turn, were described by their parents as engaging in less appropriate pragmatic behaviors. The significant indirect effect suggests that inhibitory control predicts the application of pragmatic language through its effect on hyperactive-impulsive behavior, which in turn may interfere with a child’s ability to effectively apply his or her pragmatic knowledge.

Figure 2.

The mediational role of symptoms of hyperactivity-impulsivity.

Discussion

ADHD is a clinically heterogeneous disorder that is frequently associated with impairments in other domains of function. Case in point, one recent study reported that 82% of school-aged youth with ADHD experience communicative impairments relative to 3.6% of typically developing youth (Helland, Biringer, Helland, & Heimann, 2012). This is consistent with other work suggesting that some aspects of the communicative impairments may be as common in ADHD as they are in disorders defined by deficits in pragmatic language (e.g., the autistic spectrum; Geurts & Embrechts, 2008). Given the high prevalence of communicative impairments in youth with ADHD, research has sought not only to describe the specific nature of pragmatic difficulties associated with ADHD symptoms but also to isolate potential causal factors which may account for this association. Despite growing theoretical interest in the potential contribution of executive functions, and inhibitory control more specifically, to the communicative impairments that have been observed in ADHD (e.g., Geurts, Broeders, & Nieuwland, 2010; Green et al., 2014), the extent to which ADHD traits, pragmatic language, and inhibitory ability may be associated is still somewhat speculative. With few exceptions (e.g., Huang-Pollock, Mikami, Pfiffner, & McBurnett, 2009), little empirical work has explored associations among these factors simultaneously in the context of a single study—and, to our knowledge, no studies have tested the stronger claim that ADHD traits may in fact mediate an association between inhibition and social communication. As such, this study was undertaken to examine the role of inhibition vis-à-vis the pragmatic language difficulties that have been associated with ADHD traits in a non-clinical sample of preschool-aged children whose pragmatic language and inhibitory abilities are in a period of rapid development.

Consistent with our hypotheses, we found that hyperactive-impulsive traits mediated an association between inhibitory control and the application—though not knowledge—of pragmatic rules in young children. Our results provide a speculative explanation of why an underlying deficit in inhibitory control is predictive of poorer application of pragmatic language. Children who lack the ability to stop highly prepotent though inappropriate behaviors are more likely to have difficulty awaiting their turn, inhibiting urges to interrupt or intrude on the activities of others, and/or behaving in ways that are not in accordance with their own immediate desires. These hyperactive-impulsive traits may then interfere with learning how to behave appropriately in communicative settings—by, for example, making it difficult for such children to maintain a topic of conversation that is not of immediate interest or to engage in appropriate turn-taking during communicative exchanges. This suggests that while children with inhibitory deficits are more likely to experience pragmatic weaknesses, this may be especially so for those children who also demonstrate hyperactive and impulsive behaviors. Our study is an important first step in identifying hyperactive-impulsive traits as a mediator of the relationship between inhibition and pragmatic language in young children and, though we offer some suggestions regarding why hyperactive-impulsive behaviors may play this mediating role, these suggestions require further exploration in future research. Future research should also seek to understand other factors which may influence the proposed pattern of association, and more specifically, to explore if and why the pragmatic language of some children with inhibitory control difficulties is relatively unaffected (i.e., to identify factors which may protect against communicative impairments in children with poorer inhibitory ability).

Contrary to our expectations, inattentive symptoms did not emerge as a significant mediator of the relationship between inhibition and pragmatic language—even though we did find that children who displayed more inattention also showed more poorly developed pragmatic behaviors in their everyday lives (as per parent-report). Although it has been reported that pragmatic language may be more strongly associated with inattentive traits in school-aged children (Bignell & Cain, 2007), other work suggests that hyperactivity-impulsivity may be a better predictor of pragmatic competence earlier in development (Geurts & Embrechts, 2008). These seemingly discrepant findings may reflect the different trajectories along which ADHD traits emerge, with hyperactive-impulsive behaviors tending to manifest during the preschool years and inattentive behaviors becoming more apparent upon the transition to formal schooling (Nolan, Gadow, & Sprafkin, 2001). Consequently, we believe that our pattern of results may be attributable to the age range of participants in our study, and that inattention might emerge as a significant mediator of the relationship between inhibitory ability and pragmatic language in older children. Extending our age range to include school-aged children would permit exploration of age as a potential moderator of the mediation we observed, which is another avenue for future research.

Consistent with expectations, our analyses revealed that children with poorly developed inhibitory ability evidenced deficits across both measures of pragmatic language. Indeed, previous research has found inhibition to be the only executive skill, after controlling for age, associated with children’s performance in the role of a listener on a communicative task (e.g., Nilsen & Graham, 2009). It may be that inhibition allows for individuals to suppress initial notions for a communicative response to provide one which is more pragmatically appropriate. As was predicted, however, the precise nature of the relationship between inhibitory ability, ADHD traits, and pragmatic language varied depending on how the latter was examined. We differentiated between children’s knowledge of pragmatic rules, as reflected in children’s ability to formulate and provide pragmatically appropriate responses to hypothetical social situations in a child-administered task, and their ability to apply pragmatic rules effectively in more authentic social situations, as reflected in parental ratings of children’s communicative behaviors in everyday life. Interestingly, only with respect to the latter did hyperactivity-impulsivity emerge as a significant mediator. This suggests that inhibitory ability affects both facets of pragmatic language in communicative settings, but that hyperactivity-impulsivity is implicated more specifically in the appropriate use of pragmatic rules in social contexts.

Our results are consistent with previous work showing that children with high levels of ADHD traits possess age-appropriate knowledge of pragmatic language rules but experience difficulty with regard to the application of this knowledge in real-world situations. For example, Kim and Kaiser (2000) presented school-aged children with ADHD and age-matched controls a standardized task in which they were asked to provide responses to hypothetical social situations that were depicted in short narratives. Although the two groups demonstrated equivalent levels of pragmatic knowledge on the task, children with ADHD produced significantly more inappropriate communicative behaviors than control children during a subsequent free-play session with an adult conversational partner (e.g., failing to respond to questions and requests, interrupting others’ speech). The results of our study provide further evidence that the social communication difficulties associated with ADHD traits arise from the inconsistent application of pragmatic knowledge in actual social contexts rather than a knowledge deficit per se, which may have important functional implications. Indeed, the inability to use language appropriately in social contexts may prevent children with ADHD traits from engaging successfully with others (Leonard et al., 2011). ADHD traits may prevent children from effectively engaging in (and thereby, learning from) their social environments, which may, in turn, exacerbate any existing pragmatic impairments and social skills deficits.

Beyond elucidating the central role of hyperactive-impulsive traits in understanding the relationship between inhibitory ability and social communication early in development, this study has important implications for theoretical work aimed at specifying the precise way in which these factors are inter-connected. Our results support a model in which inhibitory control has a direct impact on pragmatic knowledge acquisition and an indirect impact on the application of pragmatic knowledge via hyperactive-impulsive behaviors. In this way, the mediation models put forward in our study conceptualize inhibitory control and social communication as antecedents to and consequences of hyperactivity and impulsivity, respectively. These models are consistent with current theoretical views identifying inhibitory difficulties as an etiological risk factor for ADHD and problems with social communication as a common downstream consequence of the disorder (Crosbie et al., 2008; Green et al., 2014). Because our models were tested in the context of a cross-sectional design, however, longitudinal exploration of inhibitory ability, ADHD traits, and pragmatic language would permit explicit testing of causal ordering.

This study contributes to our understanding of the pragmatic language difficulties that are commonly implicated in ADHD by highlighting inhibitory ability and hyperactive-impulsive traits as key predictors of emergent social communication in young children. Nevertheless, our conclusions should be interpreted in the context of several considerations. One consideration is that our study placed an intentionally narrow focus on just one aspect of executive functioning—that being inhibition. Inhibition is arguably the aspect of executive functioning that has shown the most robust association with ADHD (Lipszyc & Schachar, 2010), it has been identified as a likely causal factor in the development of the disorder (Crosbie et al., 2008), it has been implicated in children’s performance on communicative tasks (Nilsen & Graham, 2009), and it can be measured using psychometrically sound tools in very young children (Floyd & Kirby, 2001). Although inhibition was a logical candidate for inclusion in our study, particularly given the necessity of streamlining our battery of tasks to be suitable for use with preschoolers, the executive collective includes other skills that may also be relevant to this line of research. For example, the ability to mentally maintain goal-relevant information (i.e., working memory; Baddeley, 1992) has been associated with ADHD (e.g., Martinussen, Hayden, Hogg-Johnson, & Tannock, 2005) and pragmatic language (e.g., McInnes, Humphries, Hogg-Johnson, & Tannock, 2003), and is featured in theoretical accounts of successful social communication (Nilsen & Fecica, 2011). Thus, working memory is another aspect of executive functioning that should be considered for inclusion in future studies. A second, though related consideration, is that our battery of tasks included a single measure of each construct to minimize boredom and fatigue for our young participants. Because all measures contain some degree of error, however, a recommended practice is to administer multiple measures of a construct to examine relationships at a latent (rather than manifest) level (e.g., Cole & Preacher, 2014). This kind of latent variables approach presents some clear challenges for work involving preschool-aged children, but may be well-suited for future studies of older, school-aged participants. A third consideration relates to our assessment of pragmatic language and the extent to which our findings generalize to other measures. Given the breadth of behaviors encompassed within the domain of pragmatics, any measure of pragmatics, including the measures included in this study, will be necessarily limited. For example, our measures did not provide comprehensive assessments of non-verbal aspects of communication. Examining the extent to which these findings hold for other measures of social communication will allow for a more precise understanding of the nature of pragmatic deficits that are associated with ADHD. Finally, our results should be interpreted within the context of the characteristics of children in our sample. Nearly all of our children were Caucasian and came from families in which parents had completed at least some post-secondary education, the latter of which may be associated aspects of language development (e.g., Dollaghan et al., 1999). Furthermore, while it is noteworthy that the observed pattern of associations emerged among our variables, despite this being a typically developing sample in which low levels of concern were endorsed or observed across measures, it will be important for future studies to explore the extent to which these findings are generalizable to samples of impaired children.

In sum, our study constitutes an important step in further elucidating the precise way in which inhibitory ability, ADHD traits, and social communication are inter-related during development. We believe that broadening the scope of our work to include other executive skills and more precise measures of pragmatic language using a latent variables framework are important avenues for future research, as are expanding our age range of children and following them prospectively over time. By enhancing our understanding of the nature and causes of the pragmatic deficits experienced by children with symptoms of ADHD early in development, we may be better able to identify and implement appropriate interventions to circumvent the potentially negative social outcomes for those with communicative impairments later in life.

Footnotes

Acknowledgements

We extend our appreciation to the children and families who participated in this study, to the early childhood education staff who facilitated recruitment, to D. O’Neill for the provision of study materials, to V. Liao for assistance with data collection, and to E. Woody for statistical consultation.

Authors’ Note

The author and co-authors were involved in all stages of this project, including (but not limited to) formulation and implementation of the research design, data analytic plan, and preparation of the manuscript.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Elizabeth S. Nilsen’s research has been funded by the Ontario Mental Health Foundation New Investigator Fellowship and Social Sciences and Humanities Research Council Standard Research Grant (these grants do not have assigned Grant numbers).

Notes

Author Biographies

Ami Rints obtained her master’s degree in developmental communication science from the University of Waterloo and is currently a PhD student in clinical psychology. Her research interests focus on the implications of executive functioning for social relations in both typical and atypical development, with a particular interest in exploring these factors within the context of ADHD.

Tara McAuley is an assistant professor whose research explores the antecedents and consequences of executive functioning in typically developing children and in children with neurodevelopmental issues such as ADHD.

Elizabeth S. Nilsen is an associate professor whose research explores the communicative and cognitive skills that allow children to successfully navigate their social environments.

References

American Psychiatric Association. (2000). Diagnostic and statistical manual of mental disorders (4th ed., text rev.). Washington, DC: Author.

Arbuckle

J. L.

(2012). Amos (Version 21.0) [Computer Program]. Chicago, IL: SPSS.

Aron

A. R.

Poldrack

R. A.

(2005). The cognitive neuroscience of response inhibition: Relevance for genetic research in attention-deficit/hyperactivity disorder. Biological Psychiatry, 57, 1285-1292.

Baddeley

(1992). Working memory. Science, 255, 556-559.

Barkley

R. A.

(1997). Behavioral inhibition, sustained attention, and executive functions: Constructing a unifying theory of ADHD. Psychological Bulletin, 121, 65-94.

Berlin

Bohlin

(2002). Response inhibition, hyperactivity, and conduct problems among preschool children. Journal of Clinical Child & Adolescent Psychology, 31, 242-251.

Bignell

Cain

(2007). Pragmatic aspects of communication and language comprehension in groups of children differentiated by teacher ratings of inattention and hyperactivity. British Journal of Developmental Psychology, 25, 499-512.

Bishop

D. V. M.

Baird

(2001). Parent and teacher report of pragmatic aspects of communication: Use of the children’s communication checklist in a clinical setting. Developmental Medicine & Child Neurology, 43, 809-818.

Camarata

S. M.

Gibson

(1999). Pragmatic language deficits in attention-deficit hyperactivity disorder (ADHD). Mental Retardation and Developmental Disabilities Research Reviews, 5, 207-214.

10.

Carrow-Woolfolk

(1999). Comprehensive assessment of spoken language [Measurement instrument]. Circle Pines, MN: American Guidance Service.

11.

Cole

D. A.

Preacher

K. J.

(2014). Manifest variable path analysis: Potentially serious and misleading consequences due to uncorrected measurement error. Psychological Methods, 19, 300-315.

12.

Connor

D. F.

(2002). Preschool attention deficit hyperactivity disorder: A review of prevalence, diagnosis, neurobiology, and stimulant treatment. Journal of Developmental & Behavioral Pediatrics, 23(Suppl. 1), S1-S9.

13.

Crosbie

Pérusse

Barr

C. L.

Schachar

R. J.

(2008). Validating psychiatric endophenotypes: Inhibitory control and attention deficit hyperactivity disorder. Neuroscience & Biobehavioral Reviews, 32, 40-55.

14.

Crosbie

Schachar

(2001). Deficient inhibition as a marker for familial ADHD. American Journal of Psychiatry, 158, 1884-1890.

15.

Cunningham

C. E.

Boyle

M. H.

(2002). Preschoolers at risk for attention-deficit hyperactivity disorder and oppositional defiant disorder: Family, parenting, and behavioral correlates. Journal of Abnormal Child Psychology, 30, 555-569.

16.

Dollaghan

C. A.

Campbell

T. F.

Paradise

J. L.

Feldman

H. M.

Janosky

J. E.

Pitcairn

D. N.

Kurs-Lasky

(1999). Maternal education and measures of early speech and language. Journal of Speech, Language, and Hearing Research, 42, 1432-1443.

17.

DuPaul

G. J.

McGoey

K. E.

Eckert

T. L.

VanBrakle

(2001). Preschool children with attention-deficit/hyperactivity disorder: Impairments in behavioral, social, and school functioning. Journal of the American Academy of Child & Adolescent Psychiatry, 40, 508-515.

18.

Floyd

R. G.

Kirby

E. A.

(2001). Psychometric properties of behavioral inhibition with preschool-age children: Implications for assessment of children at risk for ADHD. Journal of Attention Disorders, 5, 79-91.

19.

Geurts

H. M.

Broeders

Nieuwland

M. S.

(2010). Thinking outside the executive functions box: Theory of mind and pragmatic abilities in attention deficit/hyperactivity disorder. European Journal of Developmental Psychology, 7, 135-151.

20.

Geurts

H. M.

Embrechts

(2008). Language profiles in ASD, SLI, and ADHD. Journal of Autism and Developmental Disorders, 38, 1931-1943.

21.

Green

B. C.

Johnson

K. A.

Bretherton

(2014). Pragmatic language difficulties in children with hyperactivity and attention problems: An integrated review. International Journal of Language & Communication Disorders, 49, 15-29.

22.

Hayes

A. F.

Scharkow

(2013). The relative trustworthiness of inferential tests of the indirect effect in statistical mediation analysis: Does method really matter? Psychological Science, 24, 1918-1927.

23.

Helland

W. A.

Biringer

Helland

Heimann

(2012). Exploring language profiles for children with ADHD and children with Asperger syndrome. Journal of Attention Disorders, 16, 34-43.

24.

Huang-Pollock

C. L.

Mikami

A. Y.

Pfiffner

McBurnett

(2009). Can executive functions explain the relationship between attention deficit hyperactivity disorder and social adjustment? Journal of Abnormal Child Psychology, 37, 679-691.

25.

Ketelaars

M. P.

Cuperus

Jansonius

Verhoeven

(2010). Pragmatic language impairment and associated behavioral problems. International Journal of Language & Communication Disorders, 45, 204-214.

26.

Kim

O. H.

Kaiser

A. P.

(2000). Language characteristics of children with ADHD. Communication Disorders Quarterly, 21, 154-165.

27.

Korkman

Kirk

Kemp

(2007). A Developmental Neuropsychological Assessment [Measurement instrument] (2nd ed.). San Antonio, TX: Harcourt Assessment.

28.

Lahey

B. B.

Pelham

W. E.

Loney

Kipp

Ehrhardt

Lee

S. S.

. . . Massetti

(2004). Three-year predictive validity of DSM-IV attention deficit hyperactivity disorder in children diagnosed at 4-6 years of age. The American Journal of Psychiatry, 161, 2014-2020.

29.

Lakes

K. D.

Swanson

J. M.

Riggs

(2012). The reliability and validity of the English and Spanish strengths and weaknesses of ADHD and normal behavior rating scales in a preschool sample: Continuum measures of hyperactivity and inattention. Journal of Attention Disorders, 16, 510-516.

30.

Landau

Milich

(1988). Social communication patterns of attention-deficit-disordered boys. Journal of Abnormal Child Psychology, 16, 69-81.

31.

Leonard

M. A.

Milich

Lorch

E. P.

(2011). The role of pragmatic language use in mediating the relation between hyperactivity and inattention in social skills problems. Journal of Speech, Language, and Hearing Research, 54, 567-579.

32.

Lipszyc

Schachar

(2010). Inhibitory control and psychopathology: A meta-analysis of studies using the stop-signal task. Journal of the International Neuropsychological Society, 16, 1064-1076.

33.

Martinussen

Hayden

Hogg-Johnson

Tannock

(2005). A meta-analysis of working memory impairments in children with attention-deficit/hyperactivity disorder. Journal of the American Academy of Child & Adolescent Psychiatry, 44, 377-384.

34.

McAuley

Christ

S. E.

White

D. A.

(2011). Mapping the development of response inhibition in young children using a modified day-night task. Developmental Neuropsychology, 36, 539-551.

35.

McAuley

Crosbie

Charach

Schachar

(2014). The persistence of cognitive deficits in remitted and unremitted ADHD: A case for the state-independence of response inhibition. Journal of Child Psychology and Psychiatry, 55, 292-300.

36.

McInnes

Humphries

Hogg-Johnson

Tannock

(2003). Listening comprehension and working memory are impaired in attention-deficit hyperactivity disorder irrespective of language impairment. Journal of Abnormal Child Psychology, 31, 427-443.

37.

Nigg

J. T.

(2000). On inhibition/disinhibition in developmental psychopathology: Views from cognitive and personality psychology and a working taxonomy. Psychological Bulletin, 126, 220-246.

38.

Nilsen

E. S.

Fecica

A. M.

(2011). A model of communicative perspective-taking for typical and atypical populations of children. Developmental Review, 31, 55-78.

39.

Nilsen

E. S.

Graham

S. A.

(2009). The relations between children’s communicative perspective-taking and executive functioning. Cognitive Psychology, 58, 220-249.

40.

Nilsen

E. S.

Mangal

MacDonald

(2013). Referential communication in children with ADHD: The role of a listener. Journal of Speech, Language, and Hearing Research, 56, 590-603.

41.

Nolan

E. E.

Gadow

K. D.

Sprafkin

(2001). Teacher reports of DSM-IV ADHD, ODD, and CD symptoms in schoolchildren. Journal of the American Academy of Child & Adolescent Psychiatry, 40, 241-249.

42.

O’Neill

D. K.

(2007). The language use inventory for young children: A parent-report measure of pragmatic language development for 18- to 47-month-old children. Journal of Speech, Language, and Hearing Research, 50, 214-228.

43.

O’Neill

D. K.

(2009). Language use inventory: An assessment of young children’s pragmatic language development for 18-to 47-month-old children [Measurement instrument]. Waterloo, Ontario, Canada: Knowledge in Development.

44.

Palfrey

J. S.

Levine

M. D.

Walker

D. K.

Sullivan

(1985). The emergence of attention deficits in early childhood: A prospective study. Journal of Developmental & Behavioral Pediatrics, 6, 339-348.

45.

Pierce

E. W.

Ewing

L. J.

Campbell

S. B.

(1999). Diagnostic status and symptomatic behavior of hard-to-manage preschool children in middle childhood and early adolescence. Journal of Clinical Child Psychology, 28, 44-57.

46.

Polanczyk

de Lima

M. S.

Horta

B. L.

Biederman

Rohde

L. A.

(2007). The worldwide prevalence of ADHD: A systematic review and metaregression analysis. The American Journal of Psychiatry, 164, 942-948.

47.

Purvis

K. L.

Tannock

(1997). Language abilities in children with attention deficit hyperactivity disorder, reading disabilities, and normal controls. Journal of Abnormal Child Psychology, 25, 133-144.

48.

Schachar

Crosbie

Barr

C. L.

Ornstein

T. J.

Kennedy

Malone

. . . Pathare

(2005). Inhibition of motor responses in siblings concordant and discordant for attention deficit hyperactivity disorder. The American Journal of Psychiatry, 162, 1076-1082.

49.

Seidman

L. J.

(2006). Neuropsychological functioning in people with ADHD across the lifespan. Clinical Psychology Review, 26, 466-485.

50.

Sonuga-Barke

E. J. S.

Dalen

Daley

Remington

(2002). Are planning, working memory, and inhibition associated with individual differences in preschool ADHD symptoms? Developmental Neuropsychology, 21, 255-272.

51.

Statistics Canada. (2014). NHS focus on geography series – Kitchener – Cambridge – Waterloo. Retrieved from http://www12.statcan.gc.ca/nhs-enm/2011/as-sa/fogs-spg/Pages/Fog.cfm?lang=E&level=3&GeoCode=541#gnr

52.

Swanson

J. M.

(n.d.). Strengths and Weaknesses of ADHD-Symptoms and Normal Behavior Rating Scale [Measurement instrument]. Available from www.adhd.net

53.

Swanson

J. M.

Schuck

Porter

M. M.

Carlson

Hartman

C. A.

Sergeant

J. A.

. . . McCleary

(2012). Categorical and dimensional definitions and evaluations of symptoms of ADHD: History of the SNAP and the SWAN rating scale. The International Journal of Educational and Psychological Assessment, 10, 51-70.

54.

Tannock

Purvis

Schachar

R. J.

(1993). Narrative abilities in children with attention deficit hyperactivity disorder and normal peers. Journal of Abnormal Child Psychology, 21, 103-117.

55.

Tannock

Schachar

(1996). Executive dysfunction as an underlying mechanism of behavior and language problems in attention deficit hyperactivity disorder. In Beitchman

J. H.

Cohen

N. J.

Konstantareas

M. M.

Tannock

(Eds.), Language, learning, and behavior disorders: Developmental, biological, and clinical perspectives (pp. 128-155). New York, NY: Cambridge University Press.

56.

Tarver

Daley

Sayal

(2014). Attention-deficit hyperactivity disorder (ADHD): An updated review of the essential facts. Child: Care, Health and Development, 40, 762-774.

57.

Thorell

L. B.

Wåhlstedt

(2006). Executive functioning deficits in relation to symptoms of ADHD and/or ODD in preschool children. Infant and Child Development, 15, 503-518.

58.

Whalen

C. K.

Henker

Collins

B. E.

McAuliffe

Vaux

(1979). Peer interaction in a structured communication task: Comparisons of normal and hyperactive boys and of methylphenidate (Ritalin) and placebo effects. Child Development, 50, 388-401.

59.

Wilens

T. E.

Biederman

Brown

Tanguay

Monuteaux

M. C.

Blake

. . . Spencer

T. J.

(2002). Psychiatric comorbidity and functioning in clinically referred preschool children and school-age youths with ADHD. Journal of the American Academy of Child & Adolescent Psychiatry, 41, 262-268.

60.

Woody

(2011). An SEM perspective on evaluating mediation: What every clinical researcher needs to know. Journal of Experimental Psychopathology, 2, 210-251.