The interactive balance between innate and experiential factors is a well worn controversy in developmental science, and even now it is possible to find proponents emphasizing the singular importance of one over the other. Rarely are these issues clearly distinguishable in a clinical evaluation. At the least, infants bring a set of innate capacities that influence how they respond to the environment and how it responds to them. The clinician is always faced with considering how intrinsic and extrinsic factors have interacted to contribute to an infant’s developmental difficulties or strengths. Infants are more vulnerable to developmental dysfunction, even with a supportive environment, if there is biological dysfunction, as in genetic disorders or severe prematurity. Conversely, even “well endowed” infants are at risk for developmental dysfunction if their environment provides inadequate or inconsistent nurturing. A combination of an impoverished or dangerous environment combined with biological or genetic risks is a significant predictor of developmental dysfunction, and as the number of risk factors increase so increases the likelihood for poor outcomes (10,11). Indeed, in an extensive review of genetic research conducted by a special task force of the American Psychological Association, it was concluded that genes, the environment, and the interaction of these two forces each play a large role in cognitive development (12). This transactional model of child development, which stresses the dynamic interplay between individual- (genes, experience) and contextual-level (aspects of environment, culture) factors, is the prevailing paradigm (13) and there are now several compelling examples of apparent gene–environment interaction including, for example, older children’s risk for depression in the face of early trauma with social support being the contextual or mediating factor (14).

Depending on the clinician’s frame of mind, maturation, or the progressive unfolding and differentiation of intrinsic capacities, presents either a complication or a challenge in the process of developmental assessment. Infants change rapidly, and the appearance of behaviors and responses can be highly variable despite certain expected sequences. Also, although very young infants begin life in a relatively undifferentiated state, within the first months, perceptual and motor systems differentiate rapidly. Implicitly, a stage-based model of infant development guides much of clinical perspectives by acknowledging that sequences of development generally are based upon orderly maturational steps that have been well described and defined. This sequence and the knowledge of when children typically achieve certain skills can be used to establish norms, against which an individual infant’s developmental skills can be contrasted. As Provence (15) has stated, “Maturation … is a necessary construct, an invisible process represented by observable behaviors.”

As described above, environment, genetic predisposition, and the interaction of both can alter maturational forces significantly. For example, we expect grasping patterns to follow an expectable, regular sequence of neurological maturation but know that the timetable for infants’ use of a particular grasp to hold a toy or explore a box is individually variable and can be highly related to the infant’s exposure. Or, although the infant may have the neurological capacity for a responsive smile and the perceptual–motor integration to extend his or her arms toward an adult, experience in interaction with the environment is a necessary factor for such observable behaviors to emerge. Also, it is true that variants of typical maturational processes exist that are not necessarily associated with later problems. For example, it is typical for infants to learn to crawl on hands and knees at eight to nine months old and then walk at 12 months. However, various alternative pathways of infant locomotion are fairly common and are not necessarily related to underlying problems, and researchers have long known that age of walking alone is not a good predictor of developmental outcomes (16).

It is important to draw a distinction between developmental processes that are primarily delayed versus those that represent a qualitative deviation from the typical progression of skills. For example, some infants and young children present a pattern of development that approximates the typical orderly progression of developmental skills, but are nonetheless developing along that track at a pace significantly behind their same-age peers. Others, however, may evidence patterns of development that are substantially different from the normal progression or show signs of qualitative differences in neuromuscular development (localized or diffuse hypotonia, abnormal reflex patterns). Significantly deviant patterns of development appear to be more common in children whose overall development is very delayed relative to chronological age expectations.

It is impossible to overstate the role of human relationships in development. The essential role of stable and nurturing human relationships is well established and universally acknowledged among researchers (17). However, most formal infant assessment techniques were developed to focus exclusively on the measurement of maturational forces, as if assuming that development proceeds relatively independent of environmental input. Thus, it is important to emphasize that every infant assessment must consider the other individuals in that infant’s life. Understanding normal, delayed, or deviant development requires some understanding of the infant’s experiences with adults. The younger the child, the more central are such individuals to the child’s safety and total well-being. Such serious events as traumatic separation, physical abuse, witnessing violence, deprivation, loss, and neglect often have devastating effects on a child’s development (18). Moreover, less extreme variations in children’s environments have profound effects on every aspect of early development, with relationships and interactions with primary caregivers being of acute importance in the very early years.

Understanding the early environment in which infants and toddlers develop is a vast topic that encompasses individual differences in parenting style, the impact of parental psychopathology such as depression, family disruption such as divorce, and how parents adapt their behaviors to the emerging developmental skills of the infant, each areas of extensive clinical scholarship and research. In this section is highlighted the areas most relevant for child psychiatrists beginning to evaluate a young child or work with the parents of an infant or toddler.

Relationships and interactions with primary caregivers, most often the mother and/or father, directly affect and dynamically interact with multiple domains of child development. These domains include attachment and social-emotional development; behavior, cooperation, and development of morality; early learning, exploration, and cognitive and language development; and health and physical development. Parents also
indirectly transmit to their children, through their impact on caregiving behaviors, the effects of more distal environmental factors such as poverty (19,20,21), parental life circumstances (21,22), and parental beliefs and attitudes (23). Parents can also shape their child’s environment indirectly through provision of stimulating and supportive social and material resources in the home environment, through choice of neighborhood, and, most crucially in early childhood, through their decisions regarding nonparental child care (21,24,25,26). Furthermore, the same distal environmental factors, like poverty, that affect parenting also limit parents’ ability to choose and shape their child’s home, neighborhood, and child care environments (17,20,21,25,26).

Infants are strongly motivated and primed to develop attachments with adult caregivers to ensure close, protective, and nurturing contact. When parenting (or primary caregiving) is reliably sensitive and contingently responsive to a child’s cues and needs, the child is more likely to develop a secure attachment. Secure attachment behaviors include using the parent as a secure base from which to comfortably explore, monitoring and seeking proximity with the parent, seeking contact eagerly after separation or if frightened, and evidence of trust and delight in the parent. When parenting is detached, intrusive, erratic, inconsistent, or rejecting, children are more likely to develop an insecure attachment, characterized by disrupted play, preoccupation with the parent’s presence, avoidance or resistance to contact and distress or anger at reunion after separation, or difficulty being comforted. Secure attachment has been associated longitudinally with development of social and emotional competence, a child’s confidence and sense of efficacy in novel or challenging situations and ability to manage stress, and greater self-efficacy, and is shown to set the stage for future positive relationships with others (16,29).

Adequate care and nurturing for an infant involves a balance among gratification, comfort, and support and the frustration inevitable in all developmental phases. Adequacy in caregiving, difficult as it is to define, generally includes attempts to mediate painful, tension-producing situations and to adjust the balance between comfort and frustration. The appropriate balance varies depending on the child’s age. For example, the infant’s frustration at not being fed immediately is different from the toddler’s frustration at being unable to reach a favorite toy, and each requires a different response from the parents. In one instance, frustration may produce a painful, tense state; in another, it may lead to an adaptive solution that enhances further learning and appropriate individuation and independence.

Parenting is associated powerfully with other domains of child development beyond attachment, although the lines between various parenting behaviors and areas of child development are blurred by dynamic transactions and integration over time. Sensitivity, contingent, appropriate responsiveness, and consistency are associated with all areas of social-emotional development (including competencies such as sustained attention, compliance, empathy, prosocial peer interactions, and emotion regulation) and also support children’s early learning. Parents promote their child’s language and cognitive abilities when they understand their child’s current abilities and structure learning opportunities accordingly, provide a rich verbal environment, and adjust their support and stimulation as the child’s capacities emerge (16,30).

Furthermore, while encouragement rather than restriction of exploration is helpful, limit setting and consistent and firm standards are also important especially for a toddler’s development of cooperation, behavioral control, and sense of conscience. Authoritative (rather than harsh or permissive) setting and enforcement of limits, incentives, and punishments, modeling of desired behaviors, and consistent routines all positively affect child’s behavioral development. Rather than a static “parenting style,” these behaviors are dynamic, adjust for changing child characteristics, and involve give and take. Toddlers’ developing cognitive capacities integrate parental expectations and standards, in turn affecting development of self-regulation, conflict management, empathy, cooperation, and awareness of the feelings and perspectives of others (16,30).

Often clinicians are not always dealing with gross parenting deficits or failures, such as in serious abuse and neglect (30a). For many infants and young children, there are crucial experiences that may have adverse effects that are much harder to identify. For example, we are only beginning to understand the critical effect of maternal depression in the first month to one year, when the mother is psychologically and sometimes physically unavailable to her infant (22,31,31). A growing body of research on the issue of caregiver mental illness, however, suggests that serious psychopathology in caregivers can significantly alter dyadic and familial interaction patterns, which in turn lead to altered developmental courses for infants. Caregiver psychopathology is a forceful example of how parental life circumstances might alter parenting and, thereby, infant and toddler development. Other factors internal to the parent—such as parenting stress (negative perceptions of child behavior, the parent–child relationship, and the self as parent) and child rearing beliefs (nonauthoritarian or progressive child-centered child rearing beliefs; such as belief that children learn actively, versus traditional or adult-centered child rearing beliefs; such as approval of uniform treatment and encouragement of obedience to authority)—also shape parenting behaviors. Life circumstances, such as single parenthood, low parental education, substance abuse, and, most pervasively, poverty, can strain the parent’s ability to respond sensitively and contingently to their infant’s cues and needs (17,20,21). Caregivers, however articulate and enlightened, may be unaware of their own difficulties in responding to their infants, or of how their mood states, worries, and frustrations affect their parental responsiveness. It is at this level that the importance of establishing a working relationship between parents and evaluator is clearest.

The early environment in which infants and toddlers develop is influenced by the broader ecological context. The broader ecological context includes the home environment, other caregiving environments such as nonparental child care, broader family circumstances and risks, and the neighborhood. These contextual influences on child development may be direct, as in the case of a nonparental caregiver’s interactions with the child, indirect, as in the effect of poverty on parenting behaviors and available resources, or both direct and indirect, as when poverty limits a parent’s child care choices, thus exposing the child to poorer quality child care.