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Introduction: Promoting Cognitive Skills During Development

Fostering the mental and emotional potential of people is an important endeavor of developmental psychologists and other professionals in the field of human development and education. There is great consensus on the idea that a society is in the tracks toward economic and social flourishing when it can provide the means to make the most of cognitive abilities and emotional well-being of its members (Beddington et al. 2008).

Throughout generations of researchers, the question of whether experience and/or environmental factors influence children’s cognitive capacities has been fundamental in the study of human development. For many years, this question brought about an intense debate on the extent to which the development of cognitive capacities is determined by genes or else depends on experience, the so-called nature vs. nurture debate. However, scientific advancements in the field of genetics in the past decades hurt this debate to death. Genes are not expressed in a vacuum milieu. Instead, epigenetic research has shown that gene expression gets turned on and off or up and down by environmental factors and that particular nurturing or lack of nurturing conditions during development can impact gene expression permanently in the life of the individual (Zhang and Meaney 2010). This research shows that heritability of cognitive skills is a flawed concept because it does not take into account this complex genes × environment interactions. Thus, the question of whether cognitive skills can be improved by training or not turns out to be a matter of finding the conditions and/or experiences that optimize cognitive development.

In the past decades, there have been an increasing number of studies aiming at examining the impact of training programs in children’s cognitive capacities. In the light of the substantial evidence provided by this research, the query of whether it is possible to enhance children’s cognitive and emotional capacities becomes a question of what are the most beneficial methods as well as a question of what are the periods of development in which intervention may be more effective.

In this chapter, we first discuss about the importance of early interventions in relation to possible developmental differences in brain plasticity. Next, we present an overview of the multiple studies that have been conducted in the past years to examine training-related gains in diverse cognitive domains through randomized controlled trials. In the last section of the chapter, we discuss the relevance of this line of research for education and clinical practice.

Plasticity During Development

Cognitive training thrives on the lure of the plastic nature of the brain. It is well known that the brain changes in response to experience or environmental stimulation. Many studies have shown the impact of family/school environment on a variety of cognitive skills, including executive attention, working memory, and intelligence, as well as the function and structure of the brain networks supporting them (Hackman et al. 2010). All these skills are crucial to school learning, and their vulnerability to poverty very likely explains the largely documented robust association between low family socioeconomic status and children’s poor academic outcomes (see Schaeffner et al., this volume). Yet, the same plastic nature of the cognitive system that enables negative experience to undermine cognitive skills also opens a window to beneficial effects of positive environment and developmental intervention. A large bulk of evidence shows that a good number of factors, from lifestyle (e.g. exercise, sleep, exposure to nature) to intervention and education, cause physiological, structural, and functional changes in the brain, which promote the development and enhancement of cognitive processes (Beddington et al. 2008).

In humans, the development of brain structures underlying superior cognitive abilities shows a developmental trajectory that extends during the first and a large proportion of the second decades of life. Developmental trajectories are not equal for brain regions supporting different cognitive skills. While structures that support more basic perceptual and sensory processes develop earlier in life, structures that support more complex processes (e.g. language, executive functions, social cognition) continue developing during late childhood and adolescence (Shaw et al. 2008). Due to this principle of brain development, the potential for brain plasticity varies over development and across brain regions. Sensitive periods of development (i.e., times during which a neural system is maximally sensitive to environmental influences) have been long believed to run in the first and second years of life. Although this might be the case for sensory systems such as vision, hearing, and aspects of language, sensitive periods for higher cognitive functions that rely on prefrontal regions are thought to stretch late into childhood and adolescence (Rice and Barone 2000). For these reasons, a child’s brain is believed to be more plastic than an adult’s; however, it is not the case that inputs to the system after the end of sensitive periods can no longer influence cognition. There are examples in different domains of a high degree of plasticity outside the sensitive period. In fact, some authors consider that the protracted development of the neural system constitutes a sustained sensitive period where environmental influences support the fine tuning and shaping of cortical circuits that underlies higher-order cognitive processes (Johnson 2011).

Training of Diverse Cognitive Skills in Childhood and Adolescence

A large bulk of studies have been carried out in the past decade in order to examine the potential benefits of cognitive training programs on the development of cognitive skills and the brain mechanisms that support them. Although studies often differ in methods, length, and intensity of intervention, most of them have targeted cognitive processes that fall under the umbrella of executive functions (EFs), namely working memory (WM), inhibitory control, executive attention, and cognitive flexibility (see Karbach and Kray, Könen et al., Strobach and Schubert, this volume). The development of EFs enables the top-down coordination and regulation of thoughts, behaviors, and emotions necessary to flexibly adapt to the demands of a changing environment. EFs have been particularly stressed in training research because of the role they play on several aspects of children’s and adolescents’ development such as social adjustment, academic competence, and mental health (Checa et al. 2008; Rothbart and Posner 2006; Moffitt et al. 2011; see Johann and Karbach, this volume).

Generally, cognitive training refers to programs designed to improve the efficiency of cognitive and brain mechanisms through practice and/or intentional instruction. Most training studies have taken a process-based approach, which consists on training specific cognitive processes by means of practicing with tasks that entail such processes. A different training strategy consists on providing instructions to develop metacognitive knowledge about task relevant procedures (see Schaeffner et al., this volume), an approach that reminds of the Vygotskian concept of scaffolding, or providing information about particular strategies that may enhance task performance (e.g., using visuo-spatial cues to improve memory; Karbach and Unger 2014).

Mostly the effects of cognitive training are studied on the performance of tasks that tap the same process or processes targeted with the intervention (near-transfer) although often effects are also measured in the performance of tasks that engage processes different from, albeit related to, those being trained (far-transfer). For instance, given that EFs are central to the development of higher-order executive functions such as reasoning, problem solving, and planning, several studies have addressed the generalization of EF training to other functions such as fluid intelligence, schooling skills, or the improvement of symptoms in the case of children with ADHD (see also De Vries and Geurts, Johann and Karbach, Katz et al., Könen et al., Schaeffner et al., this volume).

In the following sections, we provide an overview of the empirical evidence derived from studies that have examined the impact of cognitive training in infants, children, and adolescents in the past decade. We mostly cover studies using a process-based approach, a large amount of which used computer-based training programs. Also, we describe other studies that have used noncomputerized programs, some of which used scaffolding or a different type of coaching (e.g., mindfulness; see Verhaeghen, this volume). The evidence reviewed covers behavioral and neuroimaging data of the impact of training programs on three main domains of the EFs in typically developing children and clinical populations.

Working Memory

WM is perhaps the EF domain with the largest amount of training studies (see Katz et al., Könen et al., this volume). Most studies involve the use of computer-based programs aiming at practicing the ability to monitor, update, and manipulate information in memory for short periods of time by performing n-back or memory span tasks with increased levels of difficulty. In a typical n-back exercise, children are presented with sequences of stimuli and their task is to report whenever the current stimulus is similar to the one presented n items back in some particular dimension (e.g., location, color, sound, etc.; Jaeggi et al. 2011). Memory spanexercises require children to retain a series of visuospatial or verbal stimuli in memory and repeat them after a brief delay either in the same or the reversed order of presentation. Using these types of exercises for training, several studies have demonstrated enhancements of WM capacities in typically developing children (Alloway et al. 2013) as well as in children and adolescents diagnosed with attention-deficit hyperactivity disorder (ADHD; Holmes et al. 2010; Stevens et al. 2016).

Besides near-transfer effects, there is evidence that WMtraining also translates into significant benefits in different domains of children’s lives. With children and adolescents (7–15 year-olds) diagnosed with ADHD, Klingberg and colleagues have shown significant improvements on measures of nonverbal reasoning ability and inhibitory control in trained children compared to an active control group (i.e., children who only performed the initial levels of the training program; Klingberg et al. 2002, 2005). Using the same or similar training protocol, parents of children who received the treatment reported amelioration on the severity of inattentive and impulsivity/hyperactive symptoms exhibited by their children (Klingberg et al. 2005; Stevens et al. 2016; see also de Vries and Geurts, this volume).

Additionally, a few studies have tested the generalization of WM training effects into measures of verbal competence and reading performance in typically developing children (see Johann and Karbach, this volume). In one of such studies, Alloway et al. (2013) reported higher scores on fluid intelligence as well as a significant improvement on measures of verbal competence and spelling following 32 sessions of WM training. Importantly, WM gains and transfer to verbal competence and spelling were still maintained in a follow-up assessment carried out 8 months after the intervention. Transfer of WM training to reading performance has also been reported with shorter interventions (Karbach et al. 2015; Loosli et al. 2012), suggesting that the length of the program may not determine the generalization of WM training to children’s reading competence.

Some studies have also explored the neural mechanisms that underlie training-related improvements of WMin children and adolescents. Jolles et al. (2012) found that, after 6 weeks of WM training, children showed significant pre- to posttraining increases of activation in fronto-parietal structures. Likewise, in a different study conducted with adolescents diagnosed with ADHD, it was found that the magnitude of the pre- to posttraining increase of fronto-parietal activation predicted participants’ gains in WM following training. More importantly, the observed changes in neural activation were distinctly correlated with the reduction of inattention and hyperactive/impulsive symptoms after training (Stevens et al. 2016). Additionally, there is evidence that intrinsic functional connectivity between these fronto-parietal circuits and other brain regions increase after WM training over several weeks (Astle et al. 2015). Taken together, these data suggest that training may produce a broad impact in the efficacy of activation and communication between distant brain areas involved in maintaining and updating relevant information in memory.

Executive Attention and Inhibitory Control

Because of its involvement in perceptual processing and behavioral regulation, attention is central to most of our activities in daily life. Out of the broad concept of attention, executive attention refers to goal-directed behavior and action regulation and involves processes such as inhibitory control, conflict resolution, and attentional flexibility. Given that executive attention strongly develops during the first years of life (Rueda 2014), many training studies have focused on the behavioral and neural effects of cognitive interventions during the preschool years.

Although the number of studies targeting executive attention processes is still small (see Karbach and Kray, this volume), the evidence that has been gathered in the past decade suggest that these interventions translate into near (Thorell et al. 2008) and far transfer effects, particularly to measures of fluid intelligence (Liu et al. 2015; Rueda et al. 2012). In order to assess the influence of training in the plasticity of brain dynamics, some of these studies have also recorded brain activity measures using electroencephalography (EEG). Results show that training induces enhanced amplitude of attention-related ERP components (Liu et al. 2015) as well as a reduction in latency of brain responses while performing executive attention tasks (Rueda et al. 2005, 2012). Importantly, these effects are still observed 2 months after intervention without further training (Rueda et al. 2012). In a more recent study, it has been shown that training executive attention accompanied by metacognitive scaffolding provided by an adult boosts transfer of training to fluid intelligence in 5-year-old children and that the fluid IQ gain following training is predicted by changes in conflict-related brain activation in the frontal midline (Pozuelos et al. 2019; see also Schaeffner et al., this volume). This indicates that the extent of posttraining changes in the patterns of brain function is related to the generalization of training effects to other cognitive domains. However, additional research covering different age groups is needed in order to characterize the possible differences in training effects along development.

Cognitive Flexibility

Cognitive flexibility is the ability to change the course of action to adapt effectively to the changing demands of a given task or situation. This skill greatly relies on the capacity to update information in WM and implement attentional and behavioral control mechanisms. In fact, developmental studies have shown that among the executive domains, cognitive flexibility emerges later and exhibits a more protracted development, extending to late adolescence (Cepeda et al. 2001).

Most of the training studies on cognitive flexibility have been carried out with groups of school-aged children, usually starting at the age of 7 years, using a variety of exercises based on the classical task-switching paradigm. Switching tasks often involve responding to stimuli according to particular rules, which can change from one trial to the next. For example, a series of numbers are presented, and the participant is asked to indicate whether the number is odd or even (task A) if printed in red ink (cue for task A) or indicate whether the number is larger or smaller than 5 (task B) if printed in blue ink (cue for task B). The task requires flexibly switching between set of rules and adjusting response-mapping representations accordingly.

Although the number of studies is still small, evidence indicates that after switching training, children and adolescents show improvements in cognitive flexibility measures as well as far transfer effects to other cognitive domains. For instance, Karbach and Kray (2009) reported that task-switching training resulted in significant transfer to measures of response inhibition, verbal and spatial WM, and fluid intelligence. Similar results have also been reported in studies that trained children diagnosed with ADHD. Together with improvements on cognitive flexibility, children trained in task switching showed better performance on measures of inhibitory control and verbal WM (Kray et al. 2012) as well as faster choice reaction times and a tendency toward faster responses when performing an updating task (Zinke et al. 2012), compared to children who received different training protocols.

Despite of the small number of studies that have been conducted, the evidence presented here suggests that cognitive flexibility can be enhanced during development and that such beneficial effects translate into the improvement of other cognitive functions. However, given the lack of studies that investigate changes of brain function following switching-based interventions, information necessary to characterize the neural mechanisms that underlie the observed behavioral effects is lacking.

Multidomain Training

In view of the overlapping neuroanatomy of executive functions in the prefrontal cortex, a number of studies have approached cognitive training implementing a multidomain strategy. For example, Wass et al. (2011) studied the influence of a multidomain training protocol based on a number of gazed-contingent exercises that aimed to train executive attention (focused/selective attention, interference resolution, visual search) as well as WM and cognitive flexibility in infants. They found that infants significantly improved their performance on measures of cognitive control, sustained attention, and attentional control following training although no gains were found in WM.

Also, given that children diagnosed with ADHD exhibit cognitive and behavioral symptoms related to the different EF domains (see de Vries and Geurts, this volume), several studies have implemented training protocols that target two or more executive-related processes. In one of the studies, near transfer effects were limited to measures of visuospatial WM and inhibitory control while no significant differences were observed for measures of verbal WM and cognitive flexibility (Dovis et al. 2015). Furthermore, training also led to the amelioration of the frequency and severity of the ADHD symptoms (Johnstone et al. 2012). Transfer between EF tasks in multidomain training is expected given the overlapping neuroanatomy yet further research is needed for a detailed understanding of the neural dynamics underlying training benefits.

Noncomputerized Training Programs

Until now, we have described studies using process-based training interventions mostly based on computerized exercises designed to target specific cognitive functions. However, other studies have examined the effects of interventions implemented in the classroom either as incorporated to the school curricula or as extra-curricular activities performed in the school context.

An example of school curricula that incorporates exercises aimed at increasing EFs is the so-called Tools of the Mindprogram (Bodrova and Leong 2007). This is a program based on Vygotsky’s insights into development of high cognitive functions, emphasizing training of EFs through guided social interactions in the classroom. Some studies were able to evaluate the impact of the Tools program in children’s EF skills during the second year of preschool in comparison to a different curriculum implemented by the school district, which had the same academic content but did not emphasize EFs. Data revealed better performance of children in the Toolsprogram in executive control tasks (Barnett et al. 2008), an effect that was bigger in task conditions with higher executive demands (Diamond et al. 2007).

Hermida and colleagues (2015) took a somewhat different approach in a recent study. They trained teachers to include activities to promote executive functions (WM, attention, inhibitory control, and planning) in the classroom and tested both near and far transfer effects of intervention to behavioral tests of EF and academic achievement, respectively. Results failed to show significant differences in EF performance between children in the intervention and control groups; however, they found significant differences in four of the six academic achievement areas evaluated: language and mathematics, autonomy, and socialization with peers. On a similar approach, Neville et al. (2013) implemented a family-based training program for preschoolers from low socioeconomic backgrounds. The program consisted on training sessions for parents combined with attention training for children. They found significant benefits in reducing the stress of parents as well as behavioral, social, and cognitive (language and fluid IQ) improvements in children. Also, children showed better auditory selective attention skills in a task involving brain measurements.

A different approach to promoting self-regulatory skills at school that is generating promising results is mindfulness practice (see Verhaeghen, this volume). Mindfulness is a contemplative exercise that aims at improving the ability to have a nonjudgmental awareness that arises by paying attention to the present moment (Malinowski 2013). In a randomized control study with 7- to 9-year-old children, Flook and colleagues (2010) examined the effects of mindful awareness practice on parent- and teacher-report measures of EF. They reported gains in behavioral regulation, metacognition, and executive control scores after mindfulness training for children who were less regulated before intervention. In this study, improvements were found with both teachers and parent-reported measures, suggesting that benefits of practice in children’s regulation generalized across different settings. However, other studies have reported either weak or no effects of meditation on attention and self-regulation; thus further research is needed before reaching grounded conclusions (Goyal et al. 2014).

Overall, these interventions show promising results and point to the importance of incorporating interventions to promote cognitive and self-regulation skills into school curricula (see Alloway, Robinson, and Frankenstein, this volume) and with families. Importantly, stronger effects of interventions are consistently found in children with greater difficulties. This suggests that there exist individual differences in windows of improvement. Knowing whether upper boundaries of these improvement windows depend on the developmental stage of the individual remains a future research question.

Implications of Training for the School and Clinic

Education

Children’s academic learning and school adjustment are supported by cognitive abilities such as attention, memory, and intelligence (see also Johann and Karbach, this volume). We know that attention and self-regulation skills are key to school readiness because of their power to predict later achievement in school (Duncan et al. 2007) and many other life outcomes (Moffitt et al. 2011). Age (developmental stage) and constitution (temperament and genes) are two important sources of interindividual variability that are to be taken into account to optimize learning and adjustment in schools. Abundant evidence presents attention as an integral component in the academic success of children. Variability in attentiveness and self-regulation accounts for differences in learning and socio-emotional competencies displayed in the classroom (Checa et al. 2008) as well as learning of curricular contents such as maths (Checa and Rueda 2011) and language (Franceschini et al. 2012). This evidence speaks up for the importance of promoting children’s cognitive capacities as part of the educational curricula.

The usefulness of training tools for education will increase to the extent that their development is evidence-based and guided by scientific principles. Hence, the design of training programs must align with known processes of children’s learning and cognitive development. Literature in psychological science suggests that children learn best when they are cognitively active and engaged when learning experiences are meaningful and socially interactive, and when learning is guided by a specific goal (Hirsh-Pasek et al. 2015). With the foundation of these learning pillars, psychologists and educators can take a proactive approach to the development and evaluation of intervention tools aimed to enhance children’s odds to successful learning and socio-emotional outcomes.

Prevention and Intervention

The understanding of pathophysiological mechanisms of developmental diseases offers a way through which a particular pathology may be changed. The development of efficient treatments is greatly facilitated by knowing the pathological mechanisms of diseases because once pathological mechanisms are identified, they become putative targets of intervention (see Boller et al., this volume).

Comorbidities are common in developmental disorders. For instance, deficits of executive attention appear to underlie both autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD) (Van Der Meer et al. 2012; see de Vries and Geurts, this volume). In this context, process-based training may constitute a suitable method for disease prevention and treatment. Early intervention to train executive attention in children at risk for developing these disorders may act as a general positive or protective factor such that children with strong executive attention skills have better developmental outcomes. This approach has already proven to be beneficial for children with ADHD. As discussed earlier, several studies have shown that working memory and executive control training in children with ADHD improve performance and increase neural efficiency in relevant brain circuits, although with limited transfer to behavioral symptoms and academic outcomes.

In addition, studying the impact of training on targeted function at the brain and behavior levels, and the subsequent relationship of the training effect to the clinical outcome, facilitates an understanding of mechanisms of action of particular interventions. Importantly, effectiveness of treatment has to be tested with randomized trials including treatment and placebo groups (see Cochrane and Green, Schmiedek, this volume). In such studies, interventions can be considered efficient to the extent that they revert or palliate pathological mechanisms. In turn, information on individual differences in effectiveness has the potential to help building more potent, personalized interventions.

Conclusions and Future Research

One of the greater challenges of modern societies is to find methods to foster children’s cognitive and emotional skills. In an increasingly technological world, nurturing mental wealth is a major way to prosper both economically and socially. To accomplish this objective, psychologists and educators must work together to provide individuals with tools that can optimize cognitive skills and prevent or palliate the development of psychopathologies.

Future research will be key for identifying risk factors and behavioral, cognitive, and neural markers of learning difficulties and neurodevelopmental disorders as well as to studying the factors (e.g. genetic, temperamental, etc.; see Colzato and Hommel, this volume) that determine the effectiveness of interventions designed to fight these harmful conditions. Crucially, multidisciplinary longitudinal studies are needed in order to deepen our understanding of the complex processes supporting typical and atypical development and use this knowledge to improve developmental interventions.