This study focuses on the fair decision-making of individuals with HF-ASD and IQ- and age-matched TD individuals in an UG. First, we explore the difference between HF-ASD and TD in fair decision-making. Second, we deal with the association of ToM and EF in HF-ASD and TD. Finally, we discuss the possible psychological mechanism of HF-ASD in fair decision-making, which may be different from that in TD.
4.1 The fair decision-making difference between HF-ASD and TD
The HF-ASD group accepted unfair offers at a higher rate than the TD group, while there was no significant difference between the acceptance rates for ultra-fair offers and fair offers, which was consistent with previous findings(12, 37). Researchers have found that typically developing children and adolescents usually reject unfair offers and, as a third party, tend to punish unfair individuals(38, 39). Moreover, some researchers believe that human beings show a preference for fairness when they are 12 months old and can already make decisions according to each other's distribution intentions and distribution results when they are 4 years old(40, 41).Therefore, the results of this study suggest that the development of a sense of fairness among individuals with HF-ASD lags behind that of typically developing individuals of the same age.
Previous studies have claimed that fair decision-making in children varies with age(12, 42). In this study, we found no relationship between unfair decision-making and age in either group. According to developmental psychology, Jean Piaget suggests that the concrete operational stage (7~12 years) is critical for social cognition development. In this study, most participants were in this age range, so it is difficult to account for a tendency toward unfair acceptance. Besides, although fairness can be well developed during childhood, younger children (9 and 12 years) and older adolescents (15 and 18 years) show differences in fair decision-making(43). Accordingly, the HF-ASD group and TD group were stratified by age. The results show that individuals with HF-ASD are more inclined to accept unfair distributions in childhood but not in adolescence, possibly due to the small sample size in this study. The unfair acceptance rates of the two HF-ASD age groups were compared with those of the TD age groups. The unfair acceptance rates of the childhood HF-ASD group were significantly higher than those of the childhood TD group, but no significant difference was found between the two adolescent groups, possibly because children showing TD through the age of 6 have developed a sense of fairness, while children with ASD slowly develop a sense of fairness when they are teenagers.
4.2 The association between unfair acceptance and ToM and EF in two groups
In the general population, ToM, as the basis for cooperation, is often considered to participate in fairness-related behaviours(44, 45). Accordingly, we found that the unfair acceptance rates of children and adolescents with TD were related to the GEM, that is, ToM. Individuals with ASD are often considered to lack the ability to understand the intentions of others. In previous studies, fairness-related behaviours were shown to be related to ToM development defects(46), but no consistent conclusion was found in our study. At the same time, we found that the unfair acceptance rates of children and adolescents with HF-ASD are related to BRIEF scores, which is consistent with previous results(11, 12, 14, 15). Further regression analysis shows that both GEM and working memory have an impact on the unfair acceptance rate of individuals with TD, while the interaction between the BRIEF scores of individuals with HF-ASD and age can negatively predict unfair acceptance rates.
4.3 The possible psychological mechanism of HF-ASD in fair decision-making
According to the dual-process theories of fair decision-making, intuitive processes are fast, non-logical processes independent of working memory(47). Other researchers consider emotion-related factors, such as negative emotions generated by unfair distributions, to be a result of respondents' intuitive processes(48). Reasoning is a slow process that depends on working memory and operates on information from the specific situation. In line with Pennycook et al.(22, 49), we believe that the fair decision-making of individuals with TD is affected by both intuitive processes and reasoning processes (see Fig. 2). However, compared with individuals with TD, those with HF-ASD have defects in ToM and EF. Some researchers claim that individuals with HF-ASD may avoid social stimulation due to these deficits, so they cannot follow the daily norms of social cooperation and cannot learn the concepts of fair and unfair from the social environment(37). Our study found that the interaction between the BRIEF scores of individuals with HF-ASD and age can negatively predict unfair acceptance rates. Therefore, we can conclude that the dual processing of individuals with HF-ASD differs from that of individuals with TD (see Fig. 2). Self-regulation plays a role in inhibiting intuitive processes and activating the reasoning process in dual processing. Eliran Halali et al. have shown that self-regulatory depletion, which results from inhibiting related tasks before UG experiments, leads to an increase in the rejection rate of unfair distribution(50). BRIEF scores represent the degree of effective self-regulation through effective inhibition to change cognition and then regulate emotion and behaviour. In individuals with HF-ASD, the BRI reveals deficits. Therefore, we believe that intuitive processing plays a leading role in the fair decision-making of individuals with HF-ASD. In addition, individuals with HF-ASD may be more "selfish" due to defects in ToM, which makes them seem as if they are living in their own world. They consider only their own interests and losses and will not experience negative emotions in response to receiving unfair offers. Acceptance may be intuitive to these individuals, hence their higher rates of accepting unfair offers. In this research, we did not exclude HF-ASD patients who also suffered from attention deficit hyperactivity disorder (ADHD). In our opinion, when individuals with ASD comorbid with ADHD are more likely forced to undergo a series of negative social experiences regarding unfairness in social activities. In later life, negative emotions accompany similar situations. Meanwhile, behaviour management weakens with age, which leads to a failure of emotional control. In addition, the intuitive process occupies the dominant position in individuals with HF-ASD+ADHD, and experience is just a part of the intuitive process. Therefore, a selfish nature conflicts with experience, and individuals with HF-ASD+ADHD are unable to adjust and adapt, thus leading to negative emotions. Finally, individuals with HF-ASD+ADHD are unable to adjust negative emotions caused by experiences and conflicts due to poor behaviour management skills, so they are immersed in their own emotional world and experience a stronger emotional response to unfairness. Therefore, with age, their reactions to unfair events strengthen. In our sample, the dual processing mode of the HF-ASD population was dominated by intuitive processing, and this finding conflicts with previous research results on the dual processing mode of HF-ASD populations. First, the task of our study differs from those of previous studies. We use a simple gambling game that focuses on gain and loss, while previous studies have used more complex reasoning tasks (for example, if five machines need 5 minutes to make five widgets, how long will it take to make 100 machines to make 100 widgets?). Second, previous studies have focused on teens and adults over the age of 16, not children and adolescents under 16. Finally, individuals with ADHD were not strictly excluded from the HF-ASD group, so further studies are needed.
5. Limitations and future direction
Our study found no significant relationship between fair decision-making and age, but a difference between HF-ASD and TD in childhood was found, possibly due to the limited age range and sample size in this study. Studies with larger age ranges and larger samples may be more promising. Fair decision-making is a complicated social behaviour. Similarly, the results of this study show that EF and ToM cannot fully predict fair decision-making in children and adolescents with TD or HF-ASD. In addition to the factors involved in the two processes studied here, reality representation capabilities may impact the rates of accepting unfair distributions. Therefore, future research may need to analyse these factors.