What Influences Theory of Mind?
Age, but not the presence of older siblings, influences the development of theory of mind
Previous research has shown evidence that theory of mind (ToM) in children is acquired with age, and that its development may be associated with the presence of older siblings. Further, false belief tasks (FBT) have been found to be useful in assessing the presence or absence of ToM in children. This study aimed to find the association between age and the presence of older siblings and the performance on a FBT. 288 children aged 3 to 5 participated in this study. As expected, older children out-performed younger children in the FBT, suggesting an association between age and ToM. However, in contrast to expectation, children with at least one older sibling did not out-perform children with no siblings, indicating no association between older siblings and ToM. The findings suggest that consideration of various factors that may influence the development of ToM is needed.
Theory of mind (ToM) is known as the understanding of human psychology and the social world which allows the interpretation of others' actions, intentions and emotions that are unobservable (Peterson, 2000; McAlister & Peterson, 2007; Nelson, Adamson & Bakeman, 2008). ToM is crucial in dealing with everyday social interactions as it heightens one's sensibility to criticism (Lecce, Caputi & Hughes, 2011) and ability to pretend, imagine and predict, and thus enhancing the quality of and appreciation for communication (Peterson, 2000; Perner, Ruffman & Leekam, 1994).
An abundance of previous research has found evidence that ToM is not innate, but developed at a young age, most often before turning six (Peterson, 2000). A widely accepted way of assessing the absence or presence of ToM in children is the false belief tasks (FBT) in which children are required to infer others' mental states that may be inconsistent with their own knowledge of reality (Keceli Kaysili & Acarlar, 2011).
Previous studies using FBT have identified a number of variables which are associated with the development of ToM such as age and presence, number and type of siblings (Perner et al., 1994; Ruffman, Perner, Naito, Parkin & Clements, 1998). For example, Perner et al.'s (1994) study with three- to five-year-old children found that older children performed better on the FBT than did younger children, providing some evidence that ToM is developed and acquired with maturation (Perner et al., 1994; Jenkins & Astington, 1996). Further, children with siblings had a better false belief understanding (FBU) than those with no siblings, and children with two siblings performed better than those with one sibling, indicating that FBU is associated with the presence and number of siblings (Perner et al., 1994). This is supported by Dunn's (1984) finding that interaction with siblings intensifies social experience for young children, enhancing their creativity (Perner et al., 1994). Following this idea, Jenkins and Astington (1996) conducted a study which found evidence that larger family size (i.e., number of siblings) is indeed positively associated with early learning of FBU, while birth order and the age gap between siblings were not.
In contrast, Ruffman et al. (1998) conducted a series of experiments which found that, inconsistent with Jenkins and Astington's (1996) findings, birth order was a significant predictor of FBU. Their results showed that children between three and six with older siblings out-performed children without older siblings on FBT (Ruffman et al., 1998). The presence of younger siblings seemed to have no such effect (Ruffman et al,, 1998). Further, their re-analysis of Perner et al.'s (1994) experiment found that the number of older siblings had a positive association with FBU (Ruffman et al., 1998). It was suggested that older siblings assist in children's development of ToM through pretend play and discussion of feelings (Ruffman et al., 1998).
The findings of a number of later studies were consistent with those of previous research in that older children showed better FBU than did younger children, and that the presence of siblings predicted a better performance in FBT (Peterson, 2000; Cassidy, Fineberg, Brown & Perkins, 2005; McAlister & Peterson, 2007). However, inconsistencies remain on the impact of number and type of siblings on the development of ToM. For example, Peterson's (2000) study found that twins, and children with younger or older siblings within proximate age range, out-performed only-children in FBT regardless of family size. However, in another study, twins were not found to have a significant effect on FBU, while non-twin siblings were (Cassidy et al., 2005).
So far, previous research has shown evidence that age has an impact on the development of ToM, indicating that ToM is developed rather than innate (Perner et al., 1994). It is also evident that the presence, number and type of siblings may have an impact on the development of ToM, due to frequent opportunities of social interaction through playing and conversing (Peterson, 2000). Building on these findings and the assumption that FBT are indeed an adequate way of assessing the presence of ToM, this study focused on the effect of age and siblings on the performance in FBT. It was hypothesised that younger children will be more likely to fail the FBT than older children. It was also hypothesised that children with at least one older sibling will be more likely to pass the FBT than children of the same age with no older siblings.
288 children, 138 females (47.9 %) and 150 males (52.1 %), participated in the research. Each participant was recruited through personal contacts and interviewed by a pair of students enrolled in Developmental Psychology at the University of Melbourne. The age of the participants ranged from 3 to 5 years, with 81 3-year-olds, 114 4-year-olds and 93 5-year-olds. 134 children had at least one older sibling.
The study consisted of an interview-based FBT, intended to determine whether the participant had a ToM. An interview instruction sheet and answer sheet (see Appendix) were used, on which the interviewers recorded the participants' responses verbatim. A small M&M's container containing pencils was used.
Consent forms were signed by the caregivers after a brief description of the study. Then, the demographic information of the participants was collected, including age and gender of the participant, number of younger and/or older siblings aged between 12 months and 13 years, and gender of younger and/or older siblings.
After collecting demographic information, the interview/FBT was conducted. It was carried out in a quiet room with the participant's caregiver present. The interviewers talked or played with the participant to ensure that he/she was comfortable. During this rapport building conversation, the interviewer obtained the name of one of the participant's friends.
The interviewer showed the participant a container of M&M's and asked what they think is in the container. Once answered correctly (M&M's, chocolates, etc.), the interviewer revealed that there are pencils instead of M&M's, and asked the participant what is really in the container. Once answered correctly (pencils), the interviewer asked, "If you show (name of child's friend obtained earlier) this container and ask him/her what is in it, what will he/she say?" The correct answer to the question (M&M's, chocolates, etc.) indicates the success of the FBT.
After eliminating participants with missing data from the initial 368 participants, the number of participants reduced to 313. Then, children who did not correctly answer the first two interview questions were excluded, leaving 288 participants.
A chi-squared test was carried out for analysis to determine the association between age and presence of older siblings and the presence of ToM. Of the demographic information, only the age of participant (3 levels) and the presence of older siblings (2 levels) were used as categorical independent variables. The answer to the last question was used as a 2-level categorical dependent variable.
The distribution of FBU for the age groups is presented in Table 1. A chi-squared test for independence showed that there was a significant association between age group and FBU, χ2 (2, n = 288) = 75.49, p < 0.001. Examination of adjusted standardised residuals indicated that, compared to independence of variables, there were significantly more 3-year-olds who did not understand false belief and significantly more 5-year-olds who did understand false belief. Age and FBU were found to be independent of each other for 4-year-olds.
Distribution of FBU for three age groups
3 years of age
4 years of age
5 years of age
Because of the significant association between age and FBU for 3 and 5-year-olds, their data were excluded from the testing of the association between the presence of older siblings and FBU. It was expected that the association, or no association, would be more easily testable for 4-year-olds whose age was not found to be associated with FBU.
Out of 114 4-year-olds, 53 had at least one older sibling, and 61 had no older siblings. The distribution of FBU for 114 4-year-olds with or without older siblings is presented in Table 2. A chi-squared test for independence showed that there was no association between the presence of older siblings and FBU, χ2 (1, n = 114) = 0.32, p = 0.57.
Distribution of FBU for 4-year-olds with or without older siblings
4-year-olds without older sibling
4-year-olds with older sibling
The present study aimed to find the association between age and presence of older siblings and the presence of ToM. It was hypothesised that younger children will be more likely to fail the FBT than older children, and that children with at least one older sibling will be more likely to pass the FBT than children of the same age with no older siblings.
The first hypothesis was supported. There was evidence that more older children (5-year-olds) passed the FBT than younger children (3-year-olds), indicating that age is associated with the presence of ToM. No association was found between age and FBU in 4-year-olds, indicating that there was a random chance that 4-year-olds would have a ToM. This finding supports the findings of previous research and the broad idea surrounding the study of ToM within developmental psychology that ToM is acquired with age and maturation (Perner et al., 1994; Jenkins & Astington, 1996; Peterson, 2000).
The hypothesis that children with older siblings will be more likely to pass the FBT than children of the same age with no older siblings was not supported. The current study focused on 4-year-olds as it was assumed that the effect of older siblings would be more easily identifiable in 4-year-olds whose FBU was not influenced by age. No association was found between the presence of older siblings and FBU, indicating that for this sample of 4-year-olds, older siblings did not have an effect on the development of ToM.
One of the possible explanations for the unsupported hypothesis may be the frequency of social interactions. For example, previous studies have identified the possible reasons for the effect of older siblings on FBU to be related to social interactions, such as pretend play, conversing and arguing (Ruffman et al., 1998; Peterson, 2000). It was suggested that through interacting with siblings, children may learn to take the perspectives of others and expand their imagination (Ruffman et al., 1998; Peterson, 2000). Following this idea, children with older siblings would only show a more developed FBU if they are exposed to frequent interactions with their older siblings. For this study, the amount of time the children spent with their older siblings was not considered. If this information was collected and controlled, the outcome may have been different.
The social interaction factor could also be helpful in understanding why the first hypothesis (i.e., older children are more likely to pass FBT than younger children) was supported. For example, older children presumably have had more opportunities of social interaction than younger children, which may have helped the development of ToM.
On the other hand, it was suggested by Ruffman et al. (1998) that the effect of older siblings may only be influential if the younger children have already developed some kind of precondition that would let them benefit from the advantages of having older siblings. Although this precondition was not identified (Ruffman et al., 1998), it suggests that the true influence of older siblings may only be possible to examine once most possible developmental preconditions are controlled. Future studies could consider examining what such preconditions could be.
There are several other possible factors that may influence the acquisition of ToM that the present study did not consider. These factors include the children's verbal mental age (Ruffman et al., 1998), family size (Perner et al., 1994), types of FBT (Keceli Kaysili & Acarlar, 2011), social competence (Newton & Jenvey, 2011) and more.
Overall, the present study found a significant association between age and FBU, and no association between the presence of older siblings and FBU. It appears that future studies of a similar kind considering a number of different variables could offer a better insight into the study of ToM.
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