Quality early childhood education for under-two-year-olds: What should it look like? A literature review

Publication Details

Recent years have seen increasing participation of under-two-year-olds in early childhood education. This literature review draws together relevant research evidence to better understand what quality early childhood education for children under-two-years of age should look like.

Author(s): Carmen Dalli, E. Jayne White, Jean Rockel, Iris Duhn with Emma Buchanan, Susan Davidson, Sarah Ganly, Larissa Kus, and Bo Wang, Victoria University of Wellington.

Date Published: March 2011

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Chapter 3: New Knowledge from Child Development: Neurobiology and Translational Research


Technological advances over the last decades have facilitated neurobiological research including research on the brain functioning of living young children. This has re-positioned child development research at the centre of early childhood scholarship. In this chapter recent additions to child development scholarship in high quality peer-reviewed journals are reviewed with particular attention to 'translational research'. Translational research attempts to integrate new knowledge from a range of disciplines into new understandings that have implications for practical contexts and policy. Translational research has provided evidence about the interaction between experience and the developing brain, and how repeated affective experiences, of both positive and negative nature, create implicit and explicit memories which are encoded within the architecture of the brain. These become mental models that filter the way perceptions are channelled to construct responses to the world.

Discussing the effects of stress in infancy, as well as the connection between experience, brain development and emotion regulation, the chapter reviews the argument that toxic stress, or stress over which infants cannot exercise control, is a risk factor to brain development, the immune system, emotional well-being and to cognitive functioning. Toxic stress can result from low quality infant experience at home as well as from pre-natal exposure to maternal stress; it also arises in low quality non-parental early childhood settings

Cumulatively, translational research published in the last decade at the interface of neurobiological and developmental psychology suggests that (i) responsive attuned caregiving within stable relationships is the type of caregiving that facilitates both emotional and cognitive well-being, and thus learning; and (2) unresponsive, inconsistent and unstable relationships with caregiving adults, as well as repeated exposure to highly stressful environments have a negative impact on brain functioning and overall development.

There is debate about whether the first two years of life are critical periods for brain developments or, alternatively, windows of opportunity that are under-recognised as periods of learning and development.

Babies are like the raw material for a self. Each one comes with a genetic blueprint and a unique range of possibilities. There is a body programmed to develop in certain ways, but by no means an automatic programme. The baby is an interactive project not a self-powered one. (Gerhardt, 2004, p.18)

Despite the resistance of critical theorists to seeing child development as the dominant disciplinary field for understanding the experience of very young children (as noted in Chapter 2), the fast growth of knowledge emanating from this discipline about infants' and toddlers' developing brains has been difficult to ignore. Gerhardt's statement above articulates but one of a number of key insights about human development that recent neurobiological research has substantiated. As an area of active research, neurobiology has once again positioned child development research in the mainstream of early childhood scholarship.

This chapter reviews recent additions to the knowledge base of child development with particular reference to increased understandings about the interface between neurobiological and wholistic development. This is to provide a broad scholarly base that is relevant to the question of what quality early childhood education for under-two-year-olds "should look like".

3.1 Nature with nurture: The baby as an inseparable whole

One area where neurobiological inquiry has created significant new insights is in explaining the impact of early experiences on learning and development. For example, writing in Clinical Pediatrics, Henry Herrod (2007) from the Department of Pediatrics at the University of Tennessee, has suggested that neurobiological research has heralded a fundamental shift in conceptualising child development away from "a simple nature-versus-nurture situation" and towards a "nature and nurture or nature with nurture" proposition (p. 199). As Catherwood (1999) explained a decade ago:

This new understanding of brain growth provides for the first time an appreciation of how biology and the environmental content and context are inextricably linked in the very tissue of the developing brain. Many of the essential characteristics of children's learning can be more competently described from this frame of reference. (p. 31)

Neuroscientific knowledge, then, is now acknowledged to have wholistic implications for understanding development, as opposed to explaining the brain as a discreet organ. As the above quote illustrates, Gerhardt (2004, p. 305) saw one implication as being that "the baby and the care it receives make up an inseparable whole". Drawing on this knowledge base, Hugo Lagercrantz (2009), professor at the Karolinska Institute in Sweden, has refuted prior claims that infants do not have a consciousness. He has suggested that babies are not only self-aware, perceptive, emotionally competent and interactive, but they are able to retain memories, and capable of drawing on a variety of language forms in communication – both features of consciousness which were previously thought to be gained later in development. Viewed alongside Schore's (1994, 2001) insights about the encoding nature of the infant brain in the first year of life, these insights into infants' capabilities are seen to present new challenges to educationalists and to policy makers alike. For example, in a recent issue of the journal Child Development, Jack Shonkoff (2010), Chair of the American National Council on the Developing Child and renowned for his pioneering work in bringing neurobiological research into policy arenas, has suggested that policy makers need to consider ways that new information about the brain might be applied in addressing contemporary societal issues. Emphasising the recognised importance of (i) child-adult interactions; (ii) consistent and stable adult-child relationships; and (iii) the role played by young children in their own development, Shonkoff proposed a "biodevelopmental framework" (p. 358, reproduced below) that can be applied in seeking to untangle the origins of disparities in learning, behaviour and health status.


A biodevelopmental framework for understanding the origins of disparities in learning, behavior and health(see also: Center on the Developing Child, Harvard University website.)

3.2 Translational research: Bringing "the brain" and "the social" together

Neurobiological research has traditionally taken place in the context of: laboratory experiments on rodents and primates; the separate study of genes and molecular genetics; and the study of visual or audio perceptions of human infants (Fox & Rutter, 2010). Only very recently has the brain function of living young children been accessible to researchers (Meltzoff, 2009) through such innovative research practices as: magnetic resonance imaging, or MRI (Inder, 2002); robotics (Meltzoff, Kuhl, Movellan & Sejnowski, 2009); or saliva tests (Sims, Guilfoyle & Parry, 2005). New technologies have enabled investigations of neural patterns of "synaptic 'blooming' or 'pruning'" (Fox & Rutter, 2010, p. 24), gland functioning, DNA processes (Meaney, 2010), and 'event-related potentials' (ERI) (deRegnier, 2005) to name a few. Other known routes to information about the brain functioning of humans remain unused due to the invasive nature of the methods required. These include investigations of hormones such as corticotropin through spinal fluid samples; and adrenocorticotropin via blood tests (Gunnar & Donzella, 2002).

With the developing ability to access brain functioning, it is now possible to study the active brain, and its neurobiological interconnectedness, through the lens of other disciplines (e.g., developmental psychology) and thus bring together insights from distinct disciplines to explain how experience (e.g., interactions with people and environments) and biology (e.g., synaptic activity in the brain) impact on each other (Stiles, 2009). In accordance with this approach, Meltzoff (2009) has advocated for 'translational studies' as the new science of learning. Translational studies are studies that involve the cross-fertilisation of discoveries in different disciplines like psychology, education, machine learning and neuroscience and "are leading to changes in educational theory and the design of learning environments" (Meltzoff et al., 2009, p. 288): What is now known, and what can be known, is informed by the complementary nature of each field.

Translational research reviewed by Meltzoff et al. (2009) suggests that optimum brain development is strongly connected to affective relationships and stable environments during infancy and toddlerhood, and to the "three social skills that are foundational to human development but rare in animals: imitation, shared attention and empathetic understanding" (p. 285). Thus, Meltzoff et al. identify the new question for future research as being about the role of "the social" in learning: "What makes social interaction such a catalyst for learning?" (p. 288). Fox, Leavitt and Nelson (2010) further suggest that it is in these connections between the brain and human experience that the greatest insights about human development are to be found, since "changes in the environment – particularly when they are dramatic and pervasive – may have the power to alter neural connectivity and cognitive processing between systems" (p. 34). Researchers therefore argue that bringing a variety of disciplines to bear on neurobiological research has the potential to "drive a new generation of early childhood policies and practices" (Shonkoff, 2010, p. 358).

Bell and Wolfe (2004) pointed out that evidence they reviewed indicated that the underlying neural mechanisms for cognitive and emotional processes might be the same, and thus suggested that in future we need to consider these two processes as intricately bound. For example, Bell and Wolfe reported that the attentional processes of one brain system, the anterior attention system (AAS), appear to regulate both cognitive and emotional processing. In particular one brain structure associated with the AAS, the anterior circulate cortex (ACC) has two separate sub-divisions: the cognitive subdivision is activated in tasks that involve "conflict between two forms of stored information" (p. 367), while the emotional subdivision is activated by affect-related tasks. They argued that "even during infancy, the Anterior Attention System may already begin to integrate thought and behaviour and exert control on emotional experience and expression" (p. 367) and that this has implications for emotional regulation, working and long-term memory, and temperament.

These findings point to the same conclusions reached by the National Council on the Developing Child at Harvard University (2004a; 2004b; 2005;2007; Center on the Developing Child Harvard University, 2010), which aims to bring "sound and accurate science to bear on public decision-making affecting the lives of young children" (see www.developingchild.net). In a series of working papers published since 2004, The National Council on the Developing Child has presented evidence that "healthy development depends on the quality and reliability of a young child's relationships with the important people in his or her life, both within and outside the family" (2004a, p. 1).They also cite evidence that shows that "early experiences are built into our bodies" (Center on the Developing Child, 2010, p.1). Focusing on the link between emotion, the brain and the body, they noted:

emotional development is actually built into the architecture of young children's brains in response to their individual personal experiences and the influences of the environments in which they live. In fact, emotion is a biologically based aspect of human functioning that is "wired" into multiple regions of the central nervous system that have a long history in the evolution of our species. (2004b, p. 2)

Bringing together the insights of the working papers in the publication The science of early childhood development, the National Council on the Developing Child (2007) further highlighted that the active ingredient in the interactive dynamic between genes and experience is "the 'serve and return' nature of children's engagement in relationships with their parents and other caregivers in their family or community" (p. 1).

3.2.1 Toxic stress as a risk factor in infancy

One cited effect on brain development has been the damage incurred to infant brain circuits and hormonal systems from excessive and prolonged exposure to high levels of "toxic stress" (National Scientific Council on the Developing Child, 2005, p. 1). Toxic stress refers to situations in which young children are exposed to stress over which they cannot exercise control, and where they have inadequate access to advocacy and support from an adult who can soothe them. Poor quality early care, either through insensitive parenting or in stressful education and care settings (such as inadequate attachment relationships with adults), is described by several authors as a key contributor to toxic stress (Roisman et al., 2009) with the National Scientific Council on the Developing Child noting that "the relationships children have with their caregivers play critical roles in regulating stress hormone production during the early years of life" (p. 3).

Stress is often assessed through measures of levels of cortisol, which is a hormone that helps the body to manage stress and can be measured through saliva swabs. Normally, basal (i.e., measured on awakening) cortisol levels are high in early morning and reduce over the day to reach a low level in the evening and in the early phase of sleep. As stress typically increases cortisol levels normal for the time of day, cortisol has often been described as a stress-sensitive hormone (Watamura, Donzella, Alwin & Gunnar, 2003). Occasional surges of cortisol throughout the day are known to be beneficial and are associated with exciting events, including displays of affection; but continuously elevated stress hormone levels in infancy are associated with permanent "negative" brain changes that lead to elevated responses to stress throughout life, such as higher blood pressure and heart rate (Gunnar, Morison, Chisholm, & Schuder, 2001; National Scientific Council on the Developing Child, 2005). This response begins in the first months of life so that infants regularly exposed to stress demonstrate higher levels of cortisol secretions and more sustained elevations of cortisol in response to stressful situations.

As toxic stress has been identified to have a significant impact on brain areas such as the hippocampus (Bell & Wolfe, 2004) – which has an important role in long-term memory – and is able to be detected as early as three months of age (Gunnar & Donzella, 2002; Watamura et al., 2003), toxic stress has been identified as a risk factor in infancy. Watamura et al. have suggested that toxic stress can affect the immune system as well as emotional well-being, and Shonkoff (2010) added that cognitive functioning is significantly impaired when the individual is continually exposed to toxic stress. Reporting on data gathered as part of the longitudinal NICHD Study of Early Child Care and Youth Development, Roisman et al. (2009) found that both (a) higher levels of maternal insensitivity in early childhood, and (b) more time in childcare centres in the first years of life were uniquely (i.e., each, and separately but not interactively) related to lower base levels of cortisol at age 15 years. This finding is consistent with the so-called "attenuation hypothesis" which suggests that early interpersonal stressors ultimately result in the "downregulation of basal cortisol levels in later life" (p. 909).

Several studies have now been conducted to measure and understand the impact of stress during children's early years. Watamura et al.'s (2003) and Roisman et al.'s (2009) are relevant to this review because they are among the few that have investigated cortisol levels in saliva with under-two-year-olds.

Watamura et al's (2003) study involved 67 infants and toddlers across seven single-age classrooms (i.e., that separate infants and toddlers) in four full-day American child care centres. The centres were described as being of adequate to excellent quality on the ECERS scale (Harms & Clifford, 1980). Alongside saliva measures, teachers in the study completed an Infant Behaviour Questionnaire, and researchers (i) observed infants at two-minute intervals over any or all activities, and (ii) coded the children for signs of distress. For 36 of the 67 children, saliva measures taken at the childcare centre were compared with saliva measures taken in the home during the same period, thus allowing comparisons of cortisol levels across the two settings.

Watamura et al. (2003) reported four main findings:

  1. Rising cortisol levels were evident over the course of the childcare day with toddlers showing higher increases of cortisol than infants
  2. For the children for whom home data were present, the pattern of rising cortisol levels over the course of the day obtained from the childcare saliva samples was not evident in the home saliva samples, suggesting that the age-related cortisol increases were context sensitive
  3. Within the toddler age-group, children who were more involved in peer play exhibited lower cortisol levels during play experiences than at other times of the day
  4. Temperamentally "fearful" children had higher increases of cortisol levels over the course of the day than non-socially fearful children.

The results from Watamura et al's (2003) study were subsequently discussed in relation to other related studies and this reveals that the relationship between stress levels (as measured via saliva cortisol levels), age of child, childcare attendance and other factors such as temperament (particularly social fearfulness, or shyness), quality of childcare, and peer play is highly complex and not yet fully understood. For example, in relation to their first three findings, the authors noted that:

The specificity of the rising pattern of cortisol to child care but not to home settings raises the issue of what it is about full-day child care that stimulates increases in cortisol for toddlers and to some extent for young preschoolers, but not necessarily for infants or older children. One problem in answering this question is that the nature of child care changes with age because of the differing developmental demands of each age group. Thus, infant rooms confront children with a different environment from toddler rooms, which in turn are different from preschool rooms. Even if adult-to-child ratios and daily schedules were the same in infant, toddler, and preschool child care, because the children are age grouped, the social context would be different. As noted, peer play is one of the factors that differs markedly between infant and toddler age groups. We observed very little peer play among children in the infant rooms, and a markedly higher amount of peer play in the toddler rooms. Examined for infants and toddlers combined, 76 percent of the variation in peer play could be explained by its linear association with age. Just being in a toddler classroom, however, did not ensure that children would play with other children. Within the toddler age period, older toddlers spent more time in play with peers than did younger toddlers. Furthermore, within the toddler setting, children who managed to spend more of their time in play with peers had lower midmorning and midafternoon cortisol concentrations, and those who engaged in more complex social play had lower midmorning cortisol concentrations. As most toddlers exhibit a rising pattern of cortisol across the child care day, it is reasonable to conclude that the context is challenging. It seems, however, that toddlers who are managing to play more frequently and more complexly with other children are physiologically less reactive to the context. (p. 1016)

Later, commenting on their fourth finding that teacher-rated temperamental fearfulness was significantly associated with higher cortisol levels over the child care day, the authors noted the need for caution in interpreting the finding because:

Not only are [the findings] correlational, thus the direction of effect cannot be determined, but there are several studies in which shyness or social fear has failed to predict cortisol activity in young children (see Gunnar, 2001, for review). Thus, it will be important to replicate these results. (p. 1016)

Citing findings from a study of cortisol activity in a family-based childcare setting (Dettling, Parker, Lane, Sebanc & Gunnar, 2000) in which levels of cortisol had increased for half the children studied and decreased for the other half, Watamura et al. (2003) further noted that "more studies of different types of child care as well as of quality of child care settings are needed" (p. 1018) along with further consideration of the mediating impacts of temperament and age.

Roisman et al.'s (2009) study tackled some of the issues raised in Watamura et al.'s (2003) analysis. As noted earlier, Roisman et al.'s study drew on data gathered as part of the large NICHD Study of Early Child Care and Youth Development which prospectively tracked over 1,000 participants from age 1 month through to 15 years as part of a comprehensive multi-site study (see Chapter 2, section 2.1.5). Roisman et al.'s sample comprised 863 of the total 1,364 study participants for whom saliva samples were available from age one-month-old at regular intervals until the age of 3 years (14 in total) and then again at age fifteen years. At the time of gathering saliva samples, the children's caregivers were asked to concurrently record events, sleeping arrangements and medications taken. These samples were analysed together with videotaped interactions of the infants and mothers at age 5, 15, 24 and 36 months and 15 years; and temperament questionnaires were completed by the mothers of the infants at age 1 and 6 months. The study found lower levels of cortisol (measured on waking up in the morning) at age 15 years where subjects had experienced higher levels of maternal insensitivity and what they described as "high-quantity, low-quality centercare exposure" (p. 909) in the first three years of life. Although the magnitude of the predictive significance of the combination of insensitive parenting, and use of early childhood education on cortisol level at 15 years was small, the authors argued that this finding was robust and "neither sex nor difficult temperament conditioned [their] finding" (p. 916). From the point of view of this review, therefore, this finding is significant because it lends support to the attenuation hypothesis described above. In other words, low quality infant experience at home and in the early childhood education setting has far-reaching consequences for health, cognition, emotionality and associated disorders in adulthood (see also Shonkoff, 2010).

Further evidence of the connection between stress and later developmental functioning, comes from another recent American study which investigated the impact of pre-natal maternal stress on infants by taking saliva samples from 125 mothers and their full-term infants at 3, 9 and 12 months of age (Davis & Sandman, 2010). Their findings confirmed that maternal stress was related to stress in their infants suggesting that "while prenatal exposure to maternal stress and stress hormones predict development, significant associations do not emerge until 12 months of age" (p. 143). The researchers expressed their intention to follow these infants in subsequent studies to further elucidate the nature of the relationship between high levels of stress in infancy and later development.

Looking at stress in yet a different context, Gunnar and Donzella (2002) drew on three studies of infants in orphanage settings (Carlson & Earls, 1997; Gunnar et al., 2001; Kroupina, Gunnar & Johnson, 1997) to suggest that orphans living in institutional settings exhibited higher levels of cortisol than those who were adopted. Specifically, the "normal daytime rhythm" (Gunnar & Donzella, 2002, p. 214) conducive to lower stress was not evident in the orphanage as opposed to the home setting. A significant ameliorating factor, however, was tentatively suggested by Gunnar and Donzella (2002) on the basis of early results of a study of foster care subsequently published by Dozier and Bick (2007). The latter found that cortisol levels were lower in children who were placed with foster parents who had received parenting training. Dozier and Bicks' study aimed to avoid putting the neurobiological systems of already at-risk or neglected children at further risk by training foster parents to 'read' and interpret children's cues (a skill essential for intersubjectivity, as highlighted in Chapter 4). They argued that by creating a predictable interpersonal world for the fostered children, it was possible to "enhance the probability that vulnerable infants grow into healthy, well-adjusted children" (p. 415).

A number of key messages can be drawn from these studies. Firstly, it is clear that toxic stress is a risk factor in infancy. Secondly, poor quality care either at home, or in early childhood settings, or in combination, is a key contributor to toxic stress with recent analysis indicating that the negative impact of poor quality care affects children of all temperamental styles and of either sex immediately as well as later in life. Thirdly, the studies indicate that more research is needed to elucidate the mediating impact of temperament, sex and age under conditions of toxic stress. Finally, it is also clear that sensitive and attuned relationships with responsive caregiving adults provide the best context for infants and toddlers to thrive.

3.2.2 Responsive caregiving: a buffer against stress and a way of wiring up the brain for learning

Reviewing developmental studies of cortisol and behaviour in human children during the first five years of life, Gunnar and Donzella (2002) emphasised the importance of variations in the quality of care to changes in cortisol level (stress responses). Gunnar and Donzella described quality of care as "a multi-faceted construct that includes the caregiver's availability, attention to the child, sensitivity to the child's needs, structuring of the environment, and responsiveness to the child's signals" (p. 208). They argued that sensitive, responsive caregiving appeared to allow children to experience and express distress in ways that elicited help without elevating cortisol levels, while children who lacked a history of responsive caregiving were unable to elicit this help and demonstrated elevated cortisol levels in stressful situations. They concluded:

Under conditions of sensitive and responsive caregiving, the high cortisol responsivity of the newborn diminishes and it becomes difficult to provoke increases in cortisol to many stressors by the end of the first year of life. Presumably this…develops as children learn to expect that their attachment behaviours (e.g. proximity seeking) and distress reactions (e.g. crying) will elicit aid from caregivers. When cared for responsively and sensitively, children anticipate that adults will protect them and thus that they can cope with threat. (p. 215)

The buffering effect of responsive caregiving was also noticeable for children who were "temperamentally vulnerable, including children who tend to get easily angered and frustrated as well as those who tend to be fearful and anxious" (Gunnar & Donzella, 2002, p. 215).

In her review of neurobiological research at the beginning of this decade, psychoanalytic psychotherapist Sue Gerhardt (2004) reached the same conclusion. She further argued that when infants and their adult caregivers engage in joint activities that are joyously shared, infants release hormones that support the development of brain cells and neural pathways. Repeated exposure to such positive interactions lead young children to develop the ability to trust and commit to others, an insight Gerhardt used in sub-titling her book: "how affection shapes the human brain".

The following vignette taken from a report commissioned by the Canadian state of Ontario to review what was known about brain research and its implications for educational policy (McCain & Mustard, 1999) illustrates the type of positive interactions that infants and toddlers thrive on. The sensory input of the father, and his attention and responsive reading of the book, illustrate how multiple interpersonal connections can be established to stimulate the brain's neural pathways to be ready for literacy learning:

A father is reading a storybook to his toddler daughter (18 months old), who is sitting in his lap. His arms are around her, holding up the book with large colorful pictures. He is reading the words and talking about animal pictures. He waits for his daughter to point out the animal's nose and eyes. Once more, the sensations of warmth, touch, smell, vision, sound and position are wiring and sculpting the toddler's brain. The cross-wiring of the sensory stimulation to the different parts of the brain is laying the basis for language and later literacy and other functions of the brain. (McCain & Mustard, p. 34)

It is important to note that what is being highlighted in this example is that the route to literacy is through responsive interactions during reading rather than the reading activity per se. As Shonkoff (2010) has argued, learning for infants and toddlers is not a case of a binary choice between cognition or emotionality; rather it is the result of both. He suggests that early childhood programmes need to strike a balance between cognition and emotionality, the clear implication being that placing significant attention on emotional and social development assists cognition.

3.2.3 Neurobiology, implicit memory and emotion regulation

The link between brain development and emotion regulation is a strong theme in neurobiological research reported in child development journals. Campos, Frankel & Camras (2004) suggested that emotional regulation is aligned to a two-step emotional and cognitive process characterised by i) a feeling and ii) a modulating response. Emotional regulation, according to Campos et al., is a culturally determined response that draws on the cues offered by significant adults to the infant. Where emotionally attuned interactions are not provided for infants, the ability to regulate emotions is impaired, negative patterns are internalised and the infant does not learn socially acceptable behaviours. This phenomenon, in turn, has a negative consequence on relationships which, as a result, further constrain the developing brain thus creating what Turp (2006) called "black holes" (p. 306) in the architecture of the brain that can last a lifetime. (See Chapter 4 for characteristics of teacher behaviour found to be positively associated with emotion regulation).

Focusing on the issue of how negative early experiences impact on the developing brain, Siegel and Hartzell's (2003) work draws attention to how implicit and explicit memories are encoded within the architecture of the brain. They argued that experiences lay down an implicit memory that can shape the child throughout life. Siegel and Hartzell define implicit memory as already present at birth (having encoded prenatal experiences in utero), and continuing throughout the lifespan:

Implicit memory results in the creation of the particular circuits of the brain that are responsible for generating emotions, behavioral responses, perception, and probably the encoding of bodily sensations. (p. 22)

Siegel and Hartzell (2003) explained – as Gerhardt (2004) also did – that mental models are created when repeated experiences are generalised. Such models filter the way perceptions are channeled and help construct responses to the world. For example, if an infant's distress is responded to, he or she will generalise the presence of the adult as providing a sense of well-being and security. Siegel and Hartzell (2003) commented that the brain can encode implicit memory without consciously having to attend to the experience until: "by the second birthday, the further development of the prefrontal regions of the brain enables a sense of self and time to begin to develop, signaling the beginning of autobiographical memory" (p. 35) or explicit memory that is consciously recalled. In light of the impact of early experiences on implicit memory, Siegel and Hartzell emphasised the importance of ensuring that experiences in the first months of life are the most beneficial possible.

Contributing a further line of research that promises new insights about brain functioning, including in the area of memory and language development, is Meltzoff et al.'s (2009) focus on "perception-production brain systems for speech" (p. 287). Meltzoff et al. have suggested that magnetoencephalography (MEG) technology will soon enable the investigation of the effects of social interaction and sensori-motor experiences on cortical processing including in language learning. He plans to employ interactive humanoid robots to work with toddlers. These robots have the capacity to recognise both moods and activities and their use in researching toddlers' language has the potential to offer a further window of insight into this area of brain functioning.

3.3 Critical periods or windows of opportunity?

Given the accumulation of new knowledge about brain functioning, and the promise of more to come, it is perhaps not surprising that the under-two-year-old period is increasingly described as a critical and currently under-recognised period for learning and development. In yet another publication by the National Scientific Council on the Developing Child (2007), this phenomenon is described as "a succession of 'sensitive periods', each of which is associated with the formation of specific circuits that are associated with specific abilities" (p. 5).

Fox and Rutter (2010) prefer the metaphor of "windows of opportunity" rather than the term "critical periods" (p. 23). Similarly to The National Scientific Council on the Developing Child (2007), they suggest that there are periods in the early years that hold significant potential for learning and development (and, by implication, teaching). Others (see, for example, Keuroghlian & Knudsen, 2007 in their study of animals) purport that the plasticity of the brain suggests a capacity to adapt over a lifetime. Gunnar and Cheatham (2003), however, suggested that the extent of plasticity in the human brain is dependent on the level at which stress hormones function after toxic stress episodes are eliminated in the child's life – a phenomenon which is only beginning to be understood. They concluded that all that could be said at that point was that "the longer a child is neglected, the higher the degree of developmental delay" (Gunnar & Cheatham, p. 208).

Irrespective of whether damage is permanent or not, however, the consensus of recent neurobiological research appears to be that the developing brain is vulnerable to the effects of negative early childhood experiences. In other words, unresponsive, inconsistent and unstable relationships with adults coupled with repeated exposure to stressors appear to negatively affect brain development. On the other hand, responsive attuned caregiving facilitates both emotional and cognitive well-being, and thus learning.

Commenting on the evaluation of new evidence on the importance of early experience for later development in a special edition of the journal Child Development, Fox et al. (2010) noted:

To borrow an analogy from economics, by investing early and well in our children's development, we increase the rate of return later in life and in so doing improve not only the lives of individuals but of societies as well. (p. 36)

This echoes McCain and Mustard's (1999) argument presented to the Ontario government about the need to maximise 'brain power' potential through early investment in the human lifespan when the brain's development is most intense and malleable. The graphic representation of their argument, drawn by Perry (1996, cited in McCain and Mustard) is reproduced below.


3.4 Summary points

The purpose of this chapter has been to review recent additions to the scholarly base of child development that are relevant to answering the question of what quality early childhood education for under-two-year-olds should look like.

Taking on board the argument about the potential of translational research to inform and change "educational theory and the design of learning environments" (e.g., Meltzoff et al., 2009, p. 288; see also Cicchetti & Gunnar, 2009) this chapter concludes with a summary of key messages from the literature reviewed, and what these might suggest about what high quality early childhood education for under-twos should look like.

3.4.1 Key messages
  1. New insights from neuroscience highlight that the brain is not a discreet cognitive organ; rather, brain development is strongly connected to affective relationships and other environmental conditions during the early years. Thus children's development is an interactive process involving "nature and nurture or nature with nurture" (Herrod, 2009, p. 199). In Gerhardt's (2004) words: "The baby and the care it receives is an inseparable whole" (p. 305).
  2. Optimal brain development is strongly connected to sensitive responsive caregiving. A 'serve-and-return' dynamic in social interactions serves as a catalyst for learning (National Scientific Council for the Developing Child, 2005).
  3. Sensitive responsive caregiving enables emotion regulation in infants and toddlers and wires up the brain for learning (Campos et al., 2004). Lack of attuned caregiving constrains the developing brain creating "black holes" (Turp, 2006, p. 306) in the architecture of the brain that can persist throughout a lifetime.
  4. The underlying neural mechanisms for cognitive and emotional processes appear to be the same (Bell & Wolfe, 2004); this means that right from infancy, thought and behaviour are being integrated. Through implicit and explicit memory, mental models are built that act as filters for the way an infant perceives the world and responds to it.
  5. Meltzoff et al. (2009) have suggested that the new question for future research is about the role of "the social" in learning, and the factors that make social interaction a strong catalyst for learning. The foundational mechanisms for this appear to be "the three social skills … [of] imitation, shared attention, and empathetic understanding" (p. 285).
  6. Toxic stress is a risk factor in infancy and significantly impairs cognitive and emotional functioning as well as the immune system. Toxic stress occurs in situations where the child has no control over events and no access to support from an adult who can soothe them. Factors that produce toxic stress include low quality care, either at home or out of home, which prevents the development of a history of responsive attuned care.
3.4.2 What should high quality early childhood education for under-two-year-olds look like on the basis of these insights?

Based on the key messages in the literature reviewed in this chapter, two important implications arise about what high quality early childhood education for under-two-year-olds should look like.

  1. Early childhood settings for under-two-year-olds should be places where children experience sensitive responsive caregiving that is attuned to their cues, including their temperamental and age characteristics. This style of caregiving should be marked by a 'serve-and-return' dynamic that allows reciprocity in interaction, and creates what is otherwise called intersubjective understanding. (See Chapter 4 for further elaboration).
  2. Early childhood settings for under-two-year-olds should be low-stress environments that actively avoid toxic stress, or are able to buffer children against toxic stress "through supportive relationships that facilitate adaptive coping" (Shonkoff, 2010, p.359). Reviewed research implies that the best way of doing this is to have adults working with children who understand the impact of their actions on children's development and are trained to make that impact a positive one.

Shonkoff (2010) has argued that the path to these outcomes is "well marked – enhanced staff development, increased quality improvement, appropriate measures of accountability, and expanded funding to serve more children and families" (p. 362). He sees a second path as also essential: to encourage further experimentation, innovation and research which "positions current best practices as a promising starting point, not a final destination" (Shonkoff, p. 362). Shonkoff argues that both provision and research are necessary since there is much more yet to be discovered about the impact of experience on the developing brain but no time to waste in the life of an infant.


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  1. Sometimes referred to as "the corrosive effect of cortisol".
  2. The cortex is a sheet of neural tissue that is responsible for integrating sensory impulses and higher cognitive functioning, including language, memory and attention.

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