Executive function is a cognitive construct which involves goal-directed behaviour along with self-control, regulation, planning, and flexible set shifting (Welsh, Pennington, & Groisser, 1991). The relationships between self-regulation and language abilities are shown from very early period of toddlerhood (Carlson, Mandell, & Williams, 2004; Kopp, 1982; Vaughn, Kopp, & Krakow, 1984). Research has shown that children’s ability to control behaviour is positively related with language abilities such as usage of vocabulary and mental state terms at between two and three (e.g., Carlson, Mandell, et al., 2004). In their
longitudinal study, for example, Carlson, Mandell, et al. (2004) conducted a correlational study over 15 months regarding the relationships between executive function and theory of mind including linguistic abilities. Batteries of inhibitory control (both conflict and delay inhibition) were used. To measure linguistic abilities, parent questionnaires for the production of communicative and mental-state words, the levels of vocabulary and verbal ability were examined. The correlations showed that children’s use of mental state words (by parent report) was significantly related to inhibitory control at 24 months, and remained so at 39 months. Furthermore, verbal ability at 39 months also predicted performance of executive function skills. The study suggests that children’s own speech was correlated with the development of self-control. As the research shown and also mentioned earlier, it seems that execution of the executive skills may rely on verbalization at an early age. Thus, I will explore the
development of executive function by verbalization in this section.
First, control of behaviour appears initially to be influenced by external environmental demands such as explicit verbal regulation from others, and then self-verbalization without understanding of semantics influences their behaviour. Then their control of behaviour is transited to the next step in which they use language for self-regulation; that is, meanings of vocabulary function to regulate motor behaviour. As an example of this view, Tinsley and Waters (1982) conducted an experimental study in order to determine whether self-regulation during early childhood (at the age of two) was mediated by verbal instructions. For a
comparison of effects of verbalization, the children in the silent group were asked not to vocalize when they hit a peg once. In the overt verbalization group, three different
instructions were given. In the one version, the children had to say ‘one’simultaneously as they hit the peg, while in the toy version, instructions were to say ‘toy’. These differences in instructions were made to examine whether the semantics of the two words were related to control in the children’s act to hit the peg once. In the final version, the children were asked to verbalize one first and to act in order to probe whether verbalization played a role in regulating subsequent behaviour. The findings showed first that there was a significant
difference between groups; children in the overt group outperformed those of the silent group. Secondly, children’s performance in the one and toy versions was parallel. However, children who received the one-then-hit instruction showed the decreased performance. The findings seem to suggest that explicit simultaneous verbalization tended to regulate motor behaviour and, importantly children’s self-regulation at the early age was merely influenced by
vocalization regardless of an understanding of semantics.
A further example of the developmental progress in the use of verbalization comes from the research with preschool children by Kirkham, Cruess, and Diamond (2003). They conducted an analysis of a dimension-switching task with 3-year-old children who are known to show difficulty in sorting cards according to shape or colour. In a standard DCCS
(dimensional change card sort), for example, children are presented with target cards (e.g., a yellow car and a green flower) and receive test cards (e.g., yellow flowers and green cars). They are asked to sort the test cards according to one dimension (e.g., shape or colour), and then after a number of trials they are told to do by the switched dimension. With regard to the procedure, 3-year-old children tend to make errors on the later dimension maintaining the former rules (Zelazo, Frye, & Rapus, 1996). In order to explain the 3-year-olds’ difficulty, Kirkham et al. (2003) compared four conditions: standard, sleeve, label and face-up, testing whether redirection of children’s attention and increased or decreased demands of inhibition were responsible for their responses. As this section focused on verbalization, the label condition and standard version will be discussed here. In the label condition, children were asked to pronounce the relevant dimension instead of an experimenter. For example, in the standard condition, the experimenter says, “Here is a red one, where does it go?” However, this labelling was pronounced by the children, such as “a truck” or “blue” when the
experimenter asked “what’s this one?”, and before she asked “Where does it go?” That is, the relevant dimension was clarified by the children. It seems that this procedure may refocus children’s attention to the dimension of the post-switch trials and increase their ability to suppress the old rule. The findings showed that 3-year-olds’ performance on the label condition was significantly better than those on the standard task although the effect of labelling was not shown in 4-year-olds, as they showed no difficulty on the standard version (92% success). Kirkham et al. concluded that labelling by the children themselves for the relevant dimension had a facilitative effect on redirecting their focus, suggesting that verbalization may mediate young children’s regulation (Barkley, 1997).
To my knowledge there is no research suggesting the link between the mentalistic language and executive function as shown from the research on social understanding.
expressions on executive functioning. Moriguchi, Lee, and Itakura (2007) conducted a series of experiments focusing on whether young children’s performance on the DCCS task was influenced by attitudes of an adult model. In Experiment 4, 3- and 4-year-old children and an adult model performed the DCCS task. First, the children observed the adult model’s
performance by either shape or colour (i.e., pre-switch trials); however, the model performed incorrectly throughout the trials. The adult model then was asked whether she sorted cards correctly. The adult model’s response varied according to conditions. In the unconfident condition, the model expressed her uncertainty (i.e., ‘I don’t know. I am not sure.’), whereas the model responded with certainty (i.e., ‘yes’). The children then sorted cards by the
different dimension (i.e., post-switch trials). They found a significant difference in the 3-year- olds according to the conditions. When the model was confident, the 3-year-olds made perseverative errors using the old rule even though they did not perform the pre-switch trials. On the contrary, the children in the unconfident condition were more likely to perform using the new rule. The children in the unconfident condition were significantly better than those in the confident one. That is, the findings by Moriguchi et al. (2007) seemed to suggest that references to mental state guide to children’s specific behaviour (Lewis & Carpendale, 2009). Therefore, this research suggests a need to look further at the relationship between mentalistic language and executive function.
In sum, the research on toddlers seems to suggest that verbal mediation, mostly their own speech, may contribute to their regulation of thoughts and action. However, as the evidence mentioned earlier showed, it appears that the research has focused on children’s private speech, and there seems to be no sufficient evidence of the role of verbalization from others on children of the preschool age. Thus, this thesis explored whether verbal input in social interaction was a contributing factor supporting executive control. In the research on Eastern children, the researchers have reported that Northeast Asian preschoolers tended to
show higher levels of self-control than Western children (e.g., Oh & Lewis, 2008; Sabbagh et al., 2006). For better self-control skills, the researchers suggested a cultural effect which might encourage their executive skills. In order to explore one reason for this effect of culture, which would be bound to adults’ input to children, this thesis used linguistically specific suffixes which vary a speaker’s certainty. In other words, it explored whether children’s understanding of semantics to express mental states influenced their self-regulation.
This thesis also employed a relatively new paradigm, selective trust, which allows us to explore children’s cognitive development in terms of their mental processes of others’ epistemic states. Thus, in the next section, I will explore how and when children are selective in attending to and making judgments about others’ testimony.