8.6.4: Executive Functions
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Purpose of Executive Functions
Executive functions are a complex set of cognitive abilities, which enable us to coordinate mental processes, manipulate information, solve new problems, sequence information, inhibit non-useful responses and generate new strategies to accomplish goals in a flexible way (Diamond, 2012; Henry, Messer, & Nash, 2012; Miyake & Friedman, 2012). Most executive function research focuses on three core areas: inhibition; working memory and cognitive flexibility, which some suggest underpin other more complex executive functions such as planning, problem solving, reasoning, etc., (Friedman & Miyake, 2017). [1]
Executive functions play an important role in the everyday life of infants and toddlers, allowing them to focus attention on specific tasks, to engage in successful problem solving, and to plan for their next action. Executive functions begin to emerge early in infancy, with basic skills needed for executive functions emerging before three years of age, and more specific skills developing in early childhood (Garon, Bryson & Smith, 2008). It has been suggested that each component of executive function develops at its own rate across childhood and adolescence, reaching maturity at different ages (Diamond, 2013). The gradual acquisition of executive functions relate to the development of the prefrontal cortex and other brain areas from infancy to adulthood (Fiske & Holmboe, 2019; Thompson, 2016; Tsujimoto, 2008). [2] [3]
Figure \(\PageIndex{1}\) depicts the growth of executive function abilities in infants and toddlers from 9 to 30 months of age (Hendry & Holmboe, 2021). This data highlights two important findings. First, executive function abilities improve with age, a consistent finding across studies (Hendry et al., 2016; Putnam et al., 2006). As Figure \(\PageIndex{1}\) shows, there is a steady increase in executive function skill across the first thirty months. Second, there are early individual differences already evident by the end of the first year. This means that at any given age, some infants and toddlers have greater executive function abilities than others. Understanding early differences could be important as preschool and kindergarten children’s performance on executive function tests is correlated with academic achievement (for both mathematical and literacy assessments) in the U.S., South Korea, Taiwan, and China (McClelland et al., 2014; Ponitz et al., 2009; Wanless et al., 2011). [4]
Next, let’s look at the three core areas of executive function, inhibition, working memory and cognitive flexibility, more in depth.
Inhibition
Inhibition, or inhibitory control, is a child's ability to stop a dominant response and demonstrate more adaptive and/or socially acceptable behavior (Diamond, Kirkham, & Amso, 2002; Rennie, Bull, & Diamond, 2004). Inhibition is important in the successful execution of tasks by providing the child with the flexibility and freedom to choose and control their actions (Dowsett & Livesey, 2000), for instance, by waiting for one's turn, sharing or cleaning up toys before playing somewhere else. [6]
The developmental trajectory of inhibition begins towards the end of the first year of life (Diamond, 2002, Diamond et al., 2007, Garon et al., 2008, Wolfe & Bell, 2007) with research suggesting that some early forms of inhibitory and attentional control emerge already at around 6 months of age (Courage, Reynolds, & Richards, 2006; Holmboe, Bonneville-Roussy, et al., 2018). Inhibition skills develop rapidly between the ages of 22 and 33 months (Carlson, 2005; Kochanska, Murray, & Harlan, 2000), and the proportion of time children can successfully wait improves significantly between the ages of 30 and 42 months (Caughy, Mills, Owen, & Hurst, 2013). Following this, inhibition shows a rapid improvement during the toddler and preschool years (Friedman et al., 2011, Garon et al., 2008, Garon et al., 2014, Holmboe, Larkman, et al., 2018, Simpson & Riggs, 2005), increasing at a more steady pace throughout middle childhood (Best & Miller, 2010, Best et al., 2009), before eventually reaching adult levels in early adolescence (van den Wildenberg & van der Molen, 2004, Williams et al., 1999). [6] [7]
As infants and toddlers grow, caregiver–child interactions have an important impact on the development of children's inhibition skills. Well-organized infant and toddler classroom environments and caregivers' use of clear, proactive strategies in supporting behavior create predictability within the classroom that further enables the child to gain a sense of control and exhibit appropriate behavior while inhibiting more inappropriate behaviors (Salminen et al., 2021). Children's ability to show better inhibition control in classrooms also relates to the caregivers' sensitivity and responsiveness towards children's needs and developing skills. Children's feelings of frustration can be reduced by creating a safe and welcoming environment, showing interest in supporting infants’ and toddlers' autonomy, understanding their way of seeing the world, and supporting their willingness to attend to learning activities in a personally meaningful way (Hamre & Pianta, 2005; Ladd, Birch, & Buhs, 1999). These caregiver practices of sensitivity and responsiveness may further indicate to children that their own actions and decisions matter, hence sending out stronger signals of how to behave in an acceptable way. [6]
The concept of caregiver mind-mindedness is related to (but distinct from) that of sensitivity, but is also related to the development of inhibition. Mind-mindedness refers to a caregiver’s proclivity to treat an infant as an “individual with a mind rather than merely as a [child] with needs that must be satisfied” (Meins, Fernyhough, Fradley & Tuckey, 2001). For example, if, during a game of peek-a-boo, the infant signals that they are overstimulated (e.g., by turning away from the caregiver, tuning out, frantic movements, etc.), the caregiver's appropriate understanding of the behavioral signal in terms of the child’s internal states (e.g., feeling overwhelmed) is critical in guiding the caregiver's reaction. When the caregiver accurately understands the signal, they are more likely to show an attuned response: pause the game, enabling the infant's autonomic system to recover from the heightened arousal. Conversely, when the caregiver does not have a mind-minded perspective, they may not see or may misinterpret the infant's signal and are more likely to continue the peekaboo game. The infant then does not experience recovery from heightened physiological arousal in a way that is matched to his or her current state of being. [8] [9] [10]
One way to know a caregiver’s level of mind-mindedness is to measure the proportion of attuned comments in which a caregiver refers to a child’s desires, cognitions and emotions (Meins, Fernyhough, Fradley & Tuckey, 2001). Despite only about 10% of caregiver verbal comments being mind-mindedness comments that accurately reflect the child’s internal state (Helmerhorst, Colonnesi & Fukkink, 2019), caregiver mind-mindedness of infants at nine months of age predicts children’s developing inhibitory control at 2 and 3 years of age (Cheng, Lu, Archer & Wang, 2018). There are cultural differences in the level of mind-mindedness of caregivers. Mind-mindedness was lower in Chinese and Hong Kong caregivers compared to caregivers in the U.K. and Canada (Bernier, Carlson & Whipple, 2010; Hughes, Devine & Wang, 2017). [8] [9]
Working Memory
Working memory refers to a child's ability to hold information in memory long enough to successfully complete a task, for instance, remembering simple instructions and then performing accordingly (Adams, Bourke, & Willis, 1999). For a toddler, this can be seen in completing a task with two parts (e.g., “take your paintbrush to the sink and wash your hands”) or remembering simple rules in a game or in play. The basic components of working memory start to develop across the child's first year of life, while more complex working memory abilities, such as updating or manipulating representations develop during toddlerhood and throughout the preschool period (Alloway, Gathercole, Willis, & Adams, 2004; Gathercole, 1998; Pelphrey & Reznick, 2002). [6]
Cognitive Flexibility
Cognitive flexibility, the ability to shift between different tasks or goals, is considered a key aspect of executive functions, allowing individuals to regulate their thoughts and actions adaptively Jurado & Rosselli, 2007; Miyake et al., 2000). Cognitive flexibility is sometimes also referred to by shifting, attention switching, or task switching, and includes both the ability to disengage from irrelevant information in a previous task and to focus on relevant information in a forthcoming task (Monsell, 2003). Thus, cognitive flexibility enables one to think divergently, change perspective and adapt to a continuously changing environment. [11]
There is sparse research on the development of cognitive flexibility in infants and toddlers, as most research finds even 3 year olds struggle on tasks of cognitive flexibility. The Dimensional Change Card Sorting (DCCS) task is widely used to measure the cognitive flexibility of children. The DCCS task asks children to sort cards (e.g., a red rabbit and a blue boat) with one of the two target cards (e.g., a red boat and a blue rabbit) according to one rule (e.g., by color), and then after several successful trials, switch to another rule (e.g., by shape). Previous findings using the DCCS task indicated that most 3-year olds had difficulty switching between the dimensions, but by age 4, most children could successfully switch to the new rule (Perner & Lang, 2002; Zelazo, Frye & Rapus, 1996). Cognitive flexibility matures along a steep slope during early childhood (Diamond, 2006; Garon et al., 2008) and this is thought to be driven by neurodevelopmental changes in the prefrontal cortex (Diamond, 2002; Ezekiel et al., 2013). [12]
There are important cultural differences in early executive function skills. Findings from cross-cultural investigations suggest that children from Eastern cultures (e.g., Chinese) typically perform better on executive function tasks than their Western counterparts (Sabbagh et al., 2006; Oh & Lewis, 2008; Lewis et al., 2009; Lan et al., 2011; Grabell et al., 2015). Different explanations have been proposed. While children from Eastern cultures are expected to have mastery of impulse control around 2 years of age, children from Western cultures are not expected to be able to do so until the preschool years (Chen et al., 1998). This could create opportunities for Chinese children to be taught the importance of self-control (Ellefson et al., 2017) and start practicing executive function skills at an earlier age than their U.S. counterparts (Sabbagh et al., 2006). In a collectivist culture like China, children practice and learn how to behave in society through adult modeling of the “acceptable” behaviors (Jian, 2009). On the other hand, individual choices and negotiation are valued elements in caregiving practices in individualistic cultures (Greenfield et al., 2006). According to Lan and colleagues (2011), the difference of educational styles between countries (e.g., China and the U.S.) is the major reason for the variation in executive function skills. While being able to control one's behavior, attention and concentration are a central element of Chinese education, self-expression and decision-making freedom are more of the focus in U.S. education (Song & Jinyu, 2016). [13]
The overall behaviors and practices of infant and toddler caregivers have a significant role in the development of executive functions (Bernier, Carlson & Whipple, 2010; Fay-Stammbach, Hawes & Meredith, 2014). Stephanie Carlson (2003) argued that caregiving contributes to the development of executive function through three primary aspects of interaction (scaffolding behavior, stimulation, and sensitivity) and that each has different effects on executive function.
Scaffolding refers to how caregivers verbally and non-verbally guide and instruct children during challenging tasks (Lewis & Carpendale, 2009), support children’s autonomous exploration, and encourage children to make decisions autonomously to solve problems (Matte-Gagn & Bernier, 2011). For example, a caregiver might provide gentle guidance to a child frustrated by an ever-collapsing block tower by placing the larger blocks at the base. The strategies provided by caregivers tell children not only what to do, but also ways to think, guiding improvements in cognitive control, inhibition and the ability to think flexibly during problem-solving.
Sensitivity represents a caregiver’s ability to perceive and accurately interpret the signals shown explicitly or implicitly in an infant’s behavior, and to then respond appropriately (Pederson et al., 1990). Children who experience their environments as predictable and consistent are inclined to achieve higher-level self-regulation in their early lives and are more motivated to gain cognitive control (Carlson, 2003). For example, caregiver-toddler interactions that are warm and responsive predict longitudinal effortful control performance and delay of gratification (inhibition) ability (Kochanska et al., 2000; Sethi et al., 2000).
Stimulation covers the wide range of interactions between caregivers and children, such as the creation of environments for cognitive skill development through activities like reading (Bradley et al., 2011) and playing together (Rome-Flanders, Cronk & Gourde, 1995). Caregiver language has specifically been found to play a critical role in children’s later executive processing (Daneri et al., 2019; Landry et al., 2002). For example, caregiver verbal scaffolding during problem-solving tasks shows both concurrent and longitudinal associations with executive function in early childhood (Bernier et al., 2010; Hammond et al., 2012; Hughes & Ensor, 2009). This research emphasizes the importance of developmentally-appropriate activities that also challenge infants and toddlers accompanied by sensitive scaffolding by caregivers. [14] [15]
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