THE DEVELOPMENT OF COGNITIVE CONTROL

Due to its unique patterns of connectivity with many key regions of the brain, the PFC is thought to have “the ideal infrastructure for synthesising the diverse range of information needed for complex behaviour” (Miller, 2000, pg 59). The PFC as the centre of cognitive control, and may heavily influence the allocation of resources to executive functions, which increasingly come under top-down control with age (Best & Miller, 2010; Braet et al., 2009; Thompson-schill, Ramscar, & Chrysikou, 2009). Specifically, it is suggested that such top-down control is needed to override exploitative behaviours; that is, inhibiting the behaviours currently employed (Solution A), to enable more appropriate responses (Solution B) (Cohen et al., 2007; Daw et al., 2006; Miller & Cohen, 2001). Crucially, the PFC is implicated in inhibitory processes when working memory demand is high (Reynolds, O’Reilly, Cohen, & Braver, 2012; Simmonds, Pekar, & Mostofsky, 2008). This would tie in with studies which suggest not only that response prepotency affects behaviour optimisation due to difficulties with inhibiting the exploit response, but so too does complexity (See Chambers et al., 2009 for a review). The demand placed on PFC resources may make it more difficult for top-down processes to override the exploitative tendency, resulting in perseveration. Thus when the PFC is not yet at full capacity, such as in children, perseveration is quite likely as there is limited control exerted over cognition and behaviour. Conversely, in certain circumstances where behavioural responses are not already tied too closely to a known solution (Defeyter & German, 2003), or under conditions of pedagogy (Bonawitz et al., 2011; Csibra & Gergely, 2011; Wood, Kendal, & Flynn, 2013) , this lack of control can actually afford greater flexibility.

This highlights an important potential trade-off between weak and strong cognitive control: increased cognitive control allows for behavioural optimisation because it is associated with greater cognitive capacity in working memory and inhibition (e.g. Diamond & Doar , 1988), allowing the successful inhibition of suboptimal responses, and the subsequent enactment of

more optimal ones. That is, one of the main roles of the PFC is providing top-down control over behaviour, and specifically arbitrating between responses. However, as mentioned in Chapter 2, increased cognitive control also appears to be associated with decreased creative thinking (Chrysikou et al., 2013; Gopnik, Griffiths, & Lucas, 2015; Thompson-schill et al., 2009), as well as negatively interfering with learning (Doll, Hutchison, & Frank, 2011). This is likely due to top- down processing biasing cognition based on prior experience (Miller & Cohen, 2001). While this is an efficient problem solving strategy for the most part, and characterises complex cognition, relying on prior knowledge to guide behaviour (considered an exploit decision) may result in suboptimal use of external information. This external information may be capitalised on by agents engaging in exploratory strategies, such as novices (Luchins, 1942; Wiley, 1998), or those with compromised (Chrysikou et al., 2013) or limited cognitive control (Defeyter & German, 2003). For example, while young children may not effectively use prior information to guide learning, a largely inefficient strategy in complex problem solving, it may be the very thing that allows them to acquire the foundational skills and knowledge that adult cognition is built upon, for example, language competence (Romberg & Saffran, 2010).

As highlighted by Diamond (2013), a lack of creative thinking may be more closely linked to that of task switching or shifting, than difficulties with inhibition per se. This makes sense if we assume there may be some inverse relationship between inhibition and working memory, with task switching, such that with increasing cognitive control, there are differential effects on these executive functions. In this vein, controlling for age, Blackwell, Chatham, Wiseheart, & Munakata (2014) found evidence that those children who switched on a card sorting task - where children are initially asked to sort cards along one dimensions (e.g. shape) before being asked to sort along another dimension (e.g. colour) - had better working memory than those who perseverated. So far, this picture fits well with the pattern of flexibility being underlain by cognitive resource availability; however, there appears to be a developmental period in children where inhibition and task switching exhibit this inverse relationship, with stronger inhibitory control on a card sorting task linked to weaker task switching performance on a Go/No go task (Blackwell & Munakata, 2014). These authors suggest that children who switch may be attempting to proactively remember relevant information, which gives them an advantage in switching tasks (as they remember the new rule/solution). This is computationally demanding and is likely an emerging ability that is correlated with an increase in cognitive capacity (Braver, 2012). In contrast, perseverators may rely on a reactive memory strategy, only recalling information on the spot when presented with cues. In a cord sorting task, there may be a lack of specificity about

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which cue is associated with which rule, leading to poor performance (Blackwell et al., 2014; Chatham, Frank, & Munakata, 2009). However, on tasks which involve holding in mind multiple rules (such as Go/No-go) children who rely on proactive memory (top-down control) may overload their working memory system when trying to maintain and rehearse the different rules for responding or withholding a response. In contrast, as the Go/No-go task has unambiguous cues for going and stopping, reactive children may perform better, showing less perseverative errors and/or quicker reaction times.

It is important to note that this inverse relationship between task-switching and inhibition may be developmental in nature, and that adults often show correlations between inhibition and task switching abilities (e.g. Aron, Robbins, & Poldrack, 2004). However, it has been suggested that this trade-off persists into adulthood, but that it is underlain not by limited cognitive resources, but rather powerful cognitive control: it may be that our ability to store and hold in mind strong representations of goal-directed problem solving strategies slows us down on task switching. Specifically, Herd et al. (2014) proposed while increased cognitive control is associated with both improved performance on inhibition and switching tasks, strength of goal representation negatively impacts upon switching. In this sense, we may be better able to understand how creative thinking is sometimes greater in children than adults. As highlighted in Chapter 2, a lack of creative thinking is not necessarily due to limited inhibition or working memory capacities. Einstellung and functional fixedness are caused by becoming stuck on Solution A and subsequently failing to generate Solution B, but should be overcome once the agent has knowledge of B (whereas perseveration occurs despite knowledge of B). It would stand to reason that the stronger the representation of A, the more stuck you are likely to be on it (Herd et al., 2014). Young children, and those with compromised frontal regions, may not represent Solution A with the same veracity as an adult due to limited cognitive control. This decreased cognitive capacity may lead to weaker representations of A, making it less difficult to clear A from mind, and subsequently generate B.

Overall, if we are to consider task switching and inhibition processes as separable components, the prepotency and complexity of A may affect how well an individual can inhibit A, but in addition, the strength with which A and B are represented may also impact upon solution choice. In other words, there may be two ways in which Solution A is affecting behavioural flexibility: (i) Solution A affects the ability to change behaviour due to solution complexity interfering with inhibition processes, and/or (ii) the strength with which A is represented may affect the ability to switch between solutions.