Introduction
Children spend more time each day with their siblings than with their parents (Tucker et al., 2008). As a unique context for children's development, the sibling relationship is characterized by a unique combination of complementary (e.g., hierarchical) and reciprocal (e.g., egalitarian) interactions. Sibling complementary interaction is similar to the parent-child relationship. Due to the developmental gaps between siblings in physical (e.g., height, weight), cognitive (e.g., language and executive function) and social experiences (Campione-Barr, 2017; Dirks et al., 2015), sibling relationship shows hierarchical characteristics. Like parents, older brothers and sisters play the role of teachers, caretakers, and role models. In contrast, sibling reciprocal interaction is more similar to peer relationships. Because of the similarity of age and interests, sibling relationship exhibits the characteristics of equality, reciprocity, and sharing. Sibling interactions, both complementary (e.g., teaching, caregiving) and reciprocal (e.g., play, conflicts), offer children ample opportunities to learn about the human mind and effective ways to interact with the social world (Dunn, 1983; Harrist et al., 2014; Howe & Recchia, 2005; Karavasilis Karos, Howe, & Aquan-Assee, 2007). Indeed, many studies have shown that siblings influence a broad range of domains of children's development, such as peer relationship, prosocial and aggressive behaviors, and conflict-solving (e.g., Daniel et al., 2017; Dirks et al., 2015; Recchia & Howe, 2009; Smorti & Ponti, 2018).
By 3–6 years of age, typical developing children gradually acquire the ability to interpret and predict others' behaviors by their mental states (e.g., desires, emotions, and beliefs), termed as “Theory of Mind” (ToM, Wellman, 2017). In Western societies, abundant research has been conducted to identify which features of sibling (e.g., sibling number, birth order, and age range) affect target children's ToM and how sibling relationship influences children's ToM skills (Hou et al., 2020). Existing research findings have been mixed, with some supporting birth order and others supporting the age range of siblings, and two theoretical accounts have been proposed to explain how sibling contributes to ToM development (see Hou et al., 2020, for review). In China, since the One-Child Policy has been in place for nearly four decades (1979–2015), researchers have long focused on whether only children are at a disadvantage relative to children with siblings in the domain of academic achievement, personal characteristics, mental health and social adjustment (Chen et al., 1994; Falbo, 2012, Falbo, 2018; Jiao et al., 1996; Li et al., 2021; Liu & Jiang, 2021; Poston & Falbo, 1990). To our knowledge, no study has been conducted on the effects of siblings on Chinese children's ToM development. Therefore, the purpose of this exploratory study was to examine the difference in mental-state reasoning between children with a sibling and children without siblings and how sibling relationship quality influences children's social understanding in China.
It is commonly believed that sibling relationship constitute an essential context to comprehend the human mind and to practice social skills (e.g., Hou et al., 2020; Jambon et al., 2019). Based on this view, it is natural to suspect that sibling absence is a disadvantage compared with sibling presence. Numerous studies that aimed to explore sibling absence–presence contrasts have revealed inconsistent results.
Initially, Perner and his colleagues found that preschool children's performance on a false-belief task was positively correlated with the number of siblings (Perner, Ruffman, & Leekam, 1994), even after their age and verbal skills were accounted for Jenkins and Astington (1996). However, subsequent research did not replicate the positive link between ToM skills and sibling presence and found that this sibling advantage for ToM skills might be moderated by the birth order or age range of siblings. Specifically, some of the authors found that the sibling's birth order was a better predictor of ToM skills than the number of siblings (Calero et al., 2013; Lewis et al., 1996; Ruffman et al., 1998; Taumoepeau & Reese, 2014). They claimed that the older siblings could act as promoters in children's ToM development rather than younger siblings. On the contrary, other parts of the authors' study affirmed that siblings aged from one to twelve, named child-aged siblings, contribute to the development of ToM in target children (Mcalister & Peterson, 2006; McAlister & Peterson, 2013; Peterson, 2000). This finding was confirmed by a recent meta-analysis, which revealed that child-aged sibling presence could promote ToM development in children (Devine & Hughes, 2018).
Several theoretical accounts have been proposed to explain how sibling contributes to ToM development, why these “sibling effect” vary shapely. Here we address two: Apprenticeship Model and Age Threshold Model (see Hou et al., 2020, for review). The Apprenticeship Model is to explain why children with older siblings rather than younger ones show a developmental advantage in ToM. Having one or more siblings at home provides children with plenty of social opportunities that improve their knowledge about human mental states, and older siblings are particularly advantageous because they serve as social mentors to the younger “apprentices” (Perner, Ruffman, & Leekam, 1994; Ruffman et al., 1998). It emphasizes the unidirectional effect of older siblings on younger children. Younger siblings, due to their limited receptive and/or expressive language and lack of social experiences, are unable to benefit older siblings. This model is rooted in Vygotsky's theory of psychological development, which emphasizes the unilateral influence of the knowledgeable partners (e.g., parents, teachers, and older siblings) on the developing individuals (Vygotsk, 1978).
The Age Threshold Model attempts to explain why a child-aged sibling rather than an infant or adolescent sibling can enhance the understanding of minds (Kennedy, Lagattuta, & Sayfan, 2015). This model emphasizes the effect of reciprocal interactions between child-aged siblings on social understanding. When younger children reach a certain age, where both sibling dyads are qualified with the linguistic ability and social experiences that enable them to develop effective interactions (e.g., social pretend play, arguments), the siblings can promote each other's mental state understanding. Target children who have siblings frequently exposed to and participate in social life that is related to social-cognitive growth (Dunn, 2015; Peterson, 2000). This model can be traced back to Piaget's theory of cognitive development, emphasizing that peer interactions (especially conflicts) play a crucial role in social-cognitive development.
Notwithstanding, several studies revealed that there aren't significant differences between only-children and children with siblings on mental-state reasoning (e.g., Downey & Condron, 2004; Lawson & Mace, 2010), even children with one older or child-aged sibling don't have advantages over only children (e.g., Cole & Mitchell, 2000; Cutting & Dunn, 2006; Hughes & Ensor, 2005). These findings concerning the link between sibling and ToM in these mixed explorations have diverted researchers' attention from sibling presence to the moderating effect of the sibling relationship. The distinctive character of sibling relationship typically results in positive (e.g., warmth and closeness) and negative interactions (e.g., conflict and aggression) among siblings (Campione-Barr, 2017; Dirks et al., 2015). It is believed that knowledge of the human mind cannot be extended for children who are merely exposed to human society; however, active engagement in interpersonal interaction can (Carpendale & Lewis, 2004). Indeed, many studies have revealed that both positive and negative interactions between siblings can be conducive to comprehending the emotions and thoughts of others.
Positive interactions between siblings' dyads comprise a range of behaviors, such as sharing, comforting, aiding, timely response, and social pretend play (Volling & Elins, 1998). Both cross-sectional and longitudinal studies have shown that the ToM development of children can be encouraged by frequent positive interactions between siblings (Brown et al., 1996; Dunn et al., 1991; Jambon et al., 2019). To provide reasonable comfort, aiding, and timely responses, children are required to be sensitive to their sibling's needs, verbal ability, and knowledge levels, which strengthen their awareness of the self-other differences in mental states (Derksen et al., 2018; Prime et al., 2016). Moreover, social pretend play is emphasized as an essential contributor to the growth of ToM skills (Hou et al., 2020). It usually leads to mental-state talk between sibling dyads, for example, talking about the role assignments, game rules, and the mental states of roles, all of which help children to gain insight into the mental-state differences between themselves and others (e.g., siblings and game roles, Howe et al., 1998; Hughes & Dunn, 1997; Hughes & Ensor, 2005; Hughes et al., 2006; Youngblade & Dunn, 1995).
As for negative interaction between siblings, especially conflicts, whether they can accelerate mental-state understanding, may be moderated by the conflict-solving strategies adopted by sibling dyads (Foote & Holmes-Lonergan, 2003; Slomkowski & Dunn, 1992). Frequent conflicts between siblings are likely to increase hostile attributions to one another (Recchia et al., 2015), and result in conflict resolution by rivalry or aggression (Dirks et al., 2015). If sibling conflicts are solved by constructive strategies such as discussions or negotiation (which require children to take one another's desires, emotions, and opinions into consideration), they may stimulate awareness of mental-state differences between sibling dyads (Hughes et al., 2006; Ram & Ross, 2008; Recchia & Howe, 2009), providing children with opportunities to gain insight into others' mental states (Recchia & Howe, 2009).
Owing to the One-Child Policy that has been implemented in China for nearly four decades, to our knowledge, no study has been conducted on the effects of sibling conditions (e.g., sibling presence) or sibling relationship on Chinese children's ToM development. This motivated the author to find out whether children with siblings in China show the same developmental advantage in ToM as their Western counterparts. At the end of 2020, the enactment of the Universal Three-Child Policy in China led to a growing number of children growing up with one or more siblings. There is increased concern about sibling relationships in China (e.g., Chen, 2019a; Chen, Qu, & Chen, 2021; Feng et al., 2019). Against this background, the aims of the current study are to (a) explore whether the presence of siblings is an advantage for Chinese children's mental-state reasoning, and (b) to investigate whether the quality of sibling relationship would be associated with ToM skills in Chinese children.
Chinese parents usually have higher expectations for their firstborn, who are expected to act as caregivers, playmates, and role models for their younger siblings (Qian et al., 2020). According to the Apprenticeship Model, older siblings at home would provide younger children with plenty of social opportunities to improve their knowledge about human mental states (Perner, Ruffman, & Leekam, 1994; Ruffman et al., 1998). In contrast, younger children, due to their limited receptive and/or expressive language and lack of social experiences, are unable to benefit older siblings. From this, we speculate that younger siblings are more likely to benefit from having an older sibling through sibling interactions for Chinese children, but the reverse is not true. Therefore, we predicted that relative to one-children, Chinese children with an older sibling (especially a child-aged older sibling) would show superiority in ToM ability.
In addition, a recent empirical study showed that warm sibling relationships predicted children's social competence (e.g., low levels of shyness) over and above warm relationships between parents and children in China (Chen, Chen, & Wang, 2021). Therefore, we predicted that positive interactions between sibling dyads would be positively associated with the Chinese children's ToM ability.
Section snippets
Participants
Three hundred preschoolers and their mothers were recruited initially from Nanning, the capital of Guangxi Zhuang Autonomous Region, located in South China. Thirty-seven child-mother dyads were removed from the analyses because children did not complete the verbal ability task (n = 7) and/or their mother did not complete the questionnaires (n = 31). The final sample of 263 preschoolers included 113 children without siblings (Mage = 4.38 yrs., SD = 0.84, 53 boys) and 150 children with siblings (M
The role of sibling status on ToM score
Firstly, one-way analysis of variance (ANOVA) was used to explore the differences between children with siblings and children with siblings in PPVT-R, and ToM score, the results were as following (see Table 1): Two groups: (a) No sibling and (b) One sibling, no significant difference in ToM performance and age (FAge (1, 261) = 2.038, p = 0.154, η2 = 0.007; F PPVT-R (1, 261) = 2.188, p = 0.140, η2 = 0.008; F ToM (1, 261) = 3.150, p = 0.077, η2 = 0.012); Three groups: (a) No Sibling, (c)
Discussion
This research contributes to the understanding of sibling-relevant factors affecting children's ToM performance in China. This study examines how children's sibling status and sibling relationship quality may influence children's ToM performance. The first aim of this study was to verify the cultural universals of the sibling status effect (i.e., children without siblings vs. children with siblings) on ToM skills in China. Inconsistent with our hypothesis, the data revealed that having an older
CRediT authorship contribution statement
Xiao-Hui Hou: Conceptualization, Methodology, Writing – original draft, Funding acquisition. Liu-Ji Wang: Investigation, Data curation, Writing – original draft. Mei Li: Investigation, Writing – review & editing. Qian-Zhi Qin: Investigation. Ying Li: Investigation. Bin-Bin Chen: Writing – review & editing.
Acknowledgement
This work was supported by the National Natural Science Foundation of China (Grant No. 31760284), the 2019 Projects of the Guangxi Education Science “13th Five-Year Plan” (Grant No. 2019ZJY115), and the Innovation Project of Guangxi Graduate Education (Grant No. YCSW2020199).
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