Nonverbal imitation skills in children with specific language delay

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Highlights

  • We investigated nonverbal imitation in children with specific language delay.

  • Children were assessed on a range of different nonverbal imitation tasks.

  • Imitation tasks involved to a greater or lesser extent sociocognitive skills.

  • Children showed a specific difficulty with some, but not all, types of imitation.

  • Neither motor nor cognitive skills could account for poor imitation performance.

Abstract

Research in children with language problems has focussed on verbal deficits, and we have less understanding of children's deficits with nonverbal sociocognitive skills which have been proposed to be important for language acquisition. This study was designed to investigate elicited nonverbal imitation in children with specific language delay (SLD). It is argued that difficulties in nonverbal imitation, which do not involve the processing of structural aspects of language, may be indicative of sociocognitive deficits. Participants were German-speaking typically developing children (n = 60) and children with SLD (n = 45) aged 2–3½ years. A novel battery of tasks measured their ability to imitate a range of nonverbal target acts that to a greater or lesser extent involve sociocognitive skills (body movements, instrumental acts on objects, pretend acts). Significant group differences were found for all body movement and pretend act tasks, but not for the instrumental act tasks. The poorer imitative performance of the SLD sample was not explained by motor or nonverbal cognitive skills. Thus, it appeared that the nature of the task affected children's imitation performance. It is argued that the ability to establish a sense of connectedness with the demonstrator was at the core of children's imitation difficulty in the SLD sample.

Introduction

Specific language delay (SLD) is identified in young children who have slow language development that is substantially below expectations for their age level, with unknown aetiology (Whitehurst & Fischel, 1994). Some of these children outgrow their early language delays and move into the typical range of language acquisition as they get older, but others continue to struggle with persistent language problems. These can have far-reaching effects on educational achievement, social inclusion and employment opportunities (Conti-Ramsden et al., 2009, Ellis and Thal, 2008, Snowling et al., 2001). Children with specific deficits in language do not form a homogeneous group, but present with varied profiles (Leonard, 1998). Some children have primary problems with the forms and structures of language, some have problems with the meaning and social use of language and some have problems in both areas. It has been argued that specific deficits in language are the outcome of deficits in multiple underlying skills with different genetic and environmental origins (Bishop, 1998, Bishop, 2006). Research in children with language problems has focussed on verbal deficits, particularly deficits in the acquisition of lexical forms and syntactic structures of language. This is exemplified by a wealth of research on verbal imitation such as word, nonword and sentence repetition as indicators of phonological and morphosyntactic constraints (Chiat and Roy, 2007, Conti-Ramsden et al., 2001, Gathercole, 2006, Graf Estes et al., 2007). In contrast, we have less understanding of the role of deficits in nonverbal sociocognitive skills which have been proposed to be important for the acquisition of language (Baldwin, 1995, Tomasello, 1995). Sociocognitive abilities have been hypothesised to be necessary for discovering the meaning of language (Chiat, 2001), and it has been found that some young children with specific deficits in language have sociocognitive difficulties (Chiat & Roy, 2008). In this study, we focus on immediate elicited nonverbal imitation, which does not involve the processing of structural aspects of language but is assumed to rely significantly on sociocognitive abilities (Carpenter et al., 2002, Tomasello and Carpenter, 2005). Given that some children with specific deficits in language have sociocognitive deficits, we argue that at a group level children with SLD will perform poorly on nonverbal imitation tasks that entail sociocognitive skills.

In line with this reasoning, it is now well established that children with autism spectrum disorder (ASD), who are known to have sociocognitive difficulties, show deficits in different types of nonverbal imitation (Rogers and Williams, 2006, Williams et al., 2004). In contrast, there has been little exploration of nonverbal imitation skills in children with specific deficits in language. Existing studies have predominantly involved school-age children and focussed on the imitation of body movements (Hill, 1998, Marton, 2009, Vukovic et al., 2010), and no investigation has targeted the ability to imitate actions on objects. To our knowledge, only two studies have elicited nonverbal imitation in preschool-age children with SLD (Dohmen, 2007 [2–3 years]; Thal & Bates, 1988 [18–32 months]). Dohmen found that these children in contrast to typically developing (TD) children performed poorly on body movement imitation tasks. Furthermore, both investigations revealed difficulties in imitating pretend acts with substitute objects (designated as symbolic gestures by Thal and Bates). Thus, outcomes suggest that children with SLD have difficulty imitating body movements and pretend acts on substitute objects, but no study yet has systematically investigated a range of different types of nonverbal imitation including body movements, actions on objects and pretend acts.

In this paper, the term imitation is used to refer to any form of copying behaviour, ‘when one individual voluntarily reproduces behaviour observed in another who acts as the model for the form of a behaviour’ (Butterworth, 1999, p. 65). It has been argued that elicited imitation is not simply a one-to-one mimicking but rather an interpretation of an event which depends on children's abilities to perceive, map, recode and reproduce demonstrated stimuli. Hence, elicited imitation taps children's cognitive processing (Gleissner et al., 2000, Wagner et al., 2008), and children's errors in replicating target acts provide a window onto how they process demonstrated information. A range of competencies are thought to be involved in imitation behaviour, e.g. perceptual and attentional skills, memory, motor planning and execution, and the ability to read the demonstrator's intentions behind her/his actions (Decety, 2006, Hepburn and Stone, 2006, Williams et al., 2007). Since imitation behaviour is multifaceted and the nature of different imitation acts varies substantially, not all competencies are necessarily involved in the same way for all types of imitation.

At least two main functions of imitation for children's development can be differentiated: instrumental and social (Carpenter and Call, 2007, Nadel et al., 1999, Uzgiris, 1981). The instrumental function of imitation primarily serves the purpose of learning about features and affordances of objects. Information is transmitted within and across generations through imitation of more experienced humans using instruments. Here, imitation acts as an important learning tool for acquiring new skills which help to solve instrumental problems in the physical world. Instrumental acts (e.g. pressing a button of a toy police car to evoke a flashing light) focus on the observable outcome of an action on an object. The main reason for children to reproduce such actions is to achieve the observed outcome by extracting useful information from the demonstration. Accordingly, children's reactions are primarily guided by the physical outcomes of instrumental acts, and the need to connect with the demonstrator is less crucial. In contrast, the social function of imitation primarily serves the purpose of engaging socially with others in shared activities to experience connectedness, mutuality and understanding. Here, imitation is considered to facilitate children's ability to establish and maintain social relations and communication by experiencing socio-emotional engagement and practising social communicative strategies in interactions with others. Social acts (e.g. imitating funny faces) necessarily focus exclusively on the demonstrator as a person. The main reason for children to reproduce such otherwise rather purposeless actions is to receive positive social feedback and share a fun experience with the demonstrator. Taking these different functions into account, we argue that types of nonverbal imitation which serve a primarily social function rely more on sociocognitive abilities than types of nonverbal imitation which serve a primarily instrumental function. It follows from this that children with sociocognitive difficulties should perform poorly on imitation tasks with a primarily social function, whereas imitation tasks with a primarily instrumental function should be less challenging.

Based on these theoretical arguments and empirical findings, the current study set out to investigate nonverbal imitation in young children with SLD, as part of a larger longitudinal study of imitation and language in children with language problems. The key aim was to compare the performance of samples of TD children and children with SLD aged 2; 0–3; 5 years on a range of elicited immediate nonverbal imitation tasks in order to determine whether and which nonverbal imitation behaviours significantly differentiated samples. It was hypothesised that at a group level the SLD sample would perform significantly below the TD sample on imitation tasks categorised as ‘social’, while imitation tasks categorised as ‘instrumental’ would be no more challenging for the SLD sample than for the TD sample. To evaluate this hypothesis, a new assessment battery was designed which included a range of measures requiring the imitation of social and instrumental acts:

  • Social acts. These included four different types of body movements. None of these acts involved objects and none produced an observable functional outcome. All involved self-other mappings and were therefore assumed to rely on sociocognitive capacities.

  • Instrumental acts. These included common actions on familiar and unfamiliar objects. Both involved real objects, and in both cases, target acts resulted in observable unambiguous outcomes. All were therefore assumed to be relatively independent of sociocognitive capacities.

  • Hybrid acts. These comprised pretend acts on substitute objects (e.g. pretending to use a pencil as toothbrush). Like instrumental acts they involve real objects, but like social acts, they do not lead to an observable outcome, and the task was therefore categorised as hybrid. Since objects are used in decontextualised or even counterfunctional acts which do not produce an instrumental result, the imitator has to focus on the actions of a demonstrator to be able to reproduce an act. Children have to infer why a demonstrator intends to perform such an odd action, i.e. that it is fun to pretend to deal with objects as if they were something else. Therefore, it appears that pretend acts draw on sociocognitive abilities, but it is unclear whether these are crucial or merely helpful. Hybrid acts were included in the battery to explore whether children would have difficulty imitating target acts that can be seen as being on the cusp between serving an instrumental and social function.

Further, this study aimed to compare nonverbal imitation errors occurring in the TD and SLD samples, to determine whether the types of errors of children with SLD resemble those of TD children or whether they are qualitatively different, and whether the rates of errors of older children with SLD resemble those of younger TD children.

Section snippets

Procedures

Approval for the study was given by the City University School of Community and Health Sciences Research Ethics Committee. Each participant was seen individually for two to three sessions lasting 30–45 min at the child's home, nursery or clinic. Assessments were administered in a fixed order for each age range. Data collection was video recorded for the purpose of checking reliability if parents gave permission (Panasonic digital video camera NV-GS 120 3CCD 1.7 mega pixel). A questionnaire

Analysis of group differences

The first aim of this study was to compare the performance of samples of TD children and children with SLD on a range of novel nonverbal imitation tasks across three age ranges. Data was analysed using SPSS version 19. Due to violations of the underlying assumptions of normality and homogeneity in most data-sets, planned analyses of variance could not be calculated. Instead, two-tailed Mann–Whitney-U tests were used for significance testing. To calculate effect sizes, z-scores were converted

Discussion

This study compared samples of 2; 0–3; 5-year-old TD children and children with SLD on a range of nonverbal imitation abilities. Significant group differences were found on all body movement imitation tasks and the pretend acts on substitute objects task. In contrast, no significant group differences emerged for the common instrumental act tasks, apart from the item ‘stroking dolphin’. Thus, it appears that at least some children in the SLD sample had difficulty with nonverbal imitation, but

Conclusion

To the best of our knowledge, no study has previously investigated a range of different types of nonverbal imitation in children with SLD. The most significant finding of this research is that a sample of children with SLD performed significantly below their TD peers on some, but importantly not all, nonverbal imitation tasks: the more closely target acts were related to a social function, the more challenging was the reproduction, and the more closely a target act was related to a common

Acknowledgements

This research was funded by a City University London PhD studentship and an Economic and Social Research Council Postdoctoral Fellowship (ES/J001961/1). We thank children, parents, paediatricians, phoniatricians, speech and language therapists and nursery teachers who made this study possible. Many thanks to Professor Dorothy Bishop and Professor Christina Kauschke for valuable advice and feedback.

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