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infant The Neonatal Behavioral Assessment Scale (NBAS) was developed by Dr. Berry Brazelton and his colleagues and today is regarded as the most comprehensive examination of newborn behavior available. It is best described as a neurobehavioral assessment scale, designed to describe the newborn’s responses to his/her new extrauterine environment and to document the contribution of the newborn infant to the development of the emerging parent-child relationship.

The NBAS is based on the assumption that the newborn infant is both competent and complexly organized. The NBAS, therefore, does not merely provide a catalogue of newborn competencies but, over the course of serial examinations, allows us to see how the baby’s discrete behaviors are integrated into coherent patterns of behavior and development. The NBAS assesses the newborn’s behavioral repertoire with 28 behavioral items, each scored on a nine-point scale. It also includes an assessment of the infant’s neurological status on 20 items, each scored on a four-point scale. It is used to examine the effects of prematurity, low birthweight, undernutrition, and a range of pre-and perinatal risk factors, the effects of prenatal substance exposure, environmental toxins, temperament, neonatal behavior in different cultures, prediction studies, and studies of primate behavior. The Scale looks at a wide range of behaviors and is suitable for examining newborns and infants up to 2 months old. By the end of the assessment, the examiner has a behavioral “portrait” of the infant, describing the baby’s strengths, adaptive responses, and possible vulnerabilities.

Scale reveals infant’s individuality

When the Scale was published in the early 1970s, people were just beginning to appreciate the infant’s full breadth of capabilities, and the only tests available were designed to detect abnormalities. The Scale was designed to go beyond available assessments by revealing the infant’s strengths and range of individuality, while still providing a health screen.

The NBAS is based on several key assumptions. First, infants, even ones that seem vulnerable, are highly capable when they are born. “A newborn already has nine months of experience when she is born,” Dr. Brazelton said. “She is capable of controlling her behavior in order to respond to her new environment.”

Second, babies “communicate” through their behavior, which, although it may not always seem like it, is a rational language. Not only do infants respond to cues around them, like their parents’ faces, but they also take steps to control their environment, such as crying to get a response from their caregivers.

Third, infants are social organisms, individuals with their own unique qualities, ready to shape as well as be shaped by the caregiving environment.

Assessing the baby’s capabilities

In an effort to reveal the full richness of the newborn’s behavioral repertoire, the Scale was built to 28 behavioral and 18 reflex items. The exam does not yield a single score but instead assesses the baby’s capabilities across different developmental areas and describes how the baby integrates these areas as she deals with her new environment.

When infants are born they face four developmental tasks vital to their growth. The Scale examines how well the infant manages these interrelated tasks and sees if the baby may need extra caregiving support in some areas.

The most basic challenge facing newborns is to regulate their breathing, their temperature, and the rest of their autonomic system, which needs to be functioning properly before infants can concentrate on other developmental areas. High-risk infants may spend most of their energy trying to maintain their autonomic systems, so they cannot focus on other areas of growth. Sights and sounds may overtax them, so looking at their mother’s face may disturb their breathing or noise may set off tremors, startles, or color changes, signals that are assessed by the scale.

Next, infants strive to control their motor system. Inhibiting random movements and controlling activity levels lets the newborn focus her energy on other developmental tasks vital to growth. If the baby is having difficulty in this area, caregivers can help her by providing as much tactile support as necessary to help her settle down, such as holding or swaddling her. The scale assesses the quality of the baby’s tone, activity level, and reflexes.

Once the baby can manage motor behavior, she will be ready to tackle the next sphere in her developmental agenda: “state” regulation. State is a key developmental concept that describes levels of consciousness, which range from quiet sleep to full cry. The infant’s ability to control her states enables her to process and respond to information from her caregiving environment. The NBAS examiner looks at how an infant controls her states, and at the transition from one state to another.

For example, the exam reveals how an infant responds to light, sound, and touch during the sleep state. The examiner briefly shines a light in a sleeping baby’s eyes. Generally, the child blinks and squirms in irritation. When we repeat the process several times, the infant usually tunes out the stimulation and remains asleep. The baby’s ability to ignore the stimulation allows her to conserve energy and to develop. If a baby has trouble blocking out stimulation during the exam, parents will know that they need to support their child, perhaps by being quiet or keeping her from bright light.

Finally, when an infant’s autonomic, motor, and state systems are in equilibrium, she is ready to interact socially, the ultimate developmental task. The Scale shows how babies are ready to be engaged in their new world from the first moments of life. In this portion of the assessment, the examiner looks to see how a baby follows a red ball, a face, and a voice.

‘Best performance’

NBAS examiners are trained to get the best performance from the child by doing everything possible to support the infant in “succeeding.” For example, one part of the exam looks at an infant’s ability to self-console when she is upset. Some infants console themselves easily, while others have a more difficult time. If the infant cannot console herself, the examiner takes measured steps to help her. Not only do we learn how much support the infant may need at home, but also how far along the child is at completing her developmental agenda.

By the end of the exam, the examiner has developed a vibrant portrait of the newborn, which can be used to tailor caregiving to the baby’s specific physical needs and behavioral style. Does the baby like to be handled? Is the baby receptive to social interaction? Does the baby easily calm herself? “One of the important things about the Scale is that it parallels what parents are looking for,” Dr. Brazelton said. “It puts health care providers on the same wavelength as parents.”


The NBAS has been employed by researchers over the last four decades to provide a window on newborn and infant abilities. These studies have expanded our understanding of the range of variability in newborn behavior patterns and the effects of a wide range of pre-and perinatal factors on newborn behavior and development. The NBAS has been used in studies of intrauterine-growth-retarded and premature infants, for example, in studies of the effects of hyperbilirubinemia; different modes of delivery; maternal analgesia; the prenatal ingestion of marijuana, cocaine, alcohol, caffeine, and tobacco; as well as the effects of exposure to environmental polychlorinated biphenyls (PCBs). The NBAS is also used to examine the effects of postpartum depression on newborn behavior and the effects of newborn behavioral differences on the parent-child relationship. Although the NBAS was designed primarily to describe individual differences in newborn behavior, it has been used in longitudinal studies to provide a baseline or starting point against which to measure future change or continuity, as a predictor of developmental outcome. The NBAS has also been used extensively in cross-cultural studies. This body of research reveals a wide range of variability in newborn behavioral differences across cultures. Furthermore, these studies suggest that whereas the basic organizational processes in infancy may be universal, the range and form of these adaptations are shaped by the demands of each individual culture. In this way, cross-cultural studies using the NBAS have not only confirmed the bidirectional nature of development but have expanded our understanding of the range of variability in newborn behavior patterns and the diversity of child rearing practices and belief systems across settings (Brazelton and Nugent, 2011; Nugent, Petruaskas and Brazelton, 2009).


Brazelton, T.B., and Nugent, J.K. (2011). The Neonatal Behavioral Assessment Scale. Mac Keith Press, Cambridge.

The NBAS requires training to be able to administer it effectively and reliably. For more information, please visit the Training section.