Bath time is a great opportunity for parents, siblings and infants to bond, play and develop relationships. Baths also provide babies with a rich sensory environment: the feel of the water and another person's touch; the smell of their surroundings; the sound of the parents' and siblings' voices, and splashing. However, bath time is more than good clean fun.
For example, a growing body of evidence suggests that tactile stimulation improves growth and encourages the child's social, cognitive and motor development (Pelaez-Nogueras et al, 1996; Okabe et al, 2012). Odours also seem to influence behaviour and emotions (Lagercrantz and Changeux, 2009). Indeed, olfaction's unique anatomical pathway means that smell seems to influence infants' acquisition (e.g. memory) of, and ability to use, information (Sullivan et al, 2015). However, a recent survey suggests that many parents do not appreciate these benefits. Midwives may need to emphasise the potential benefits of bath time—and sensory stimulation more generally—in the child's development.
Investing in childcare
Fundamentally, animals have devised two approaches to ensure their offspring reach maturity and breed. Some play a numbers game. For example, a large (8 kg) Atlantic salmon (Salmo salar) will lay about 8800 eggs (Hendry and Cragg-Hine, 2003). Neither parent invests in bringing up their offspring. Chance determines that sufficient offspring obtain enough sustenance, and avoid predators and disease to propagate.
Other animals—including humans, orangutans, polar bears and emperor penguins—invest heavily in raising a few offspring (Hood, 2014; World Wildlife Fund, 2015). The average family size in the UK in 2012 included 1.7 dependent children—just 1-in-7 families had three or more dependent children (Office for National Statistics (ONS), 2013). For humans, childcare lasts for decades. During 2013, about 3.3 million adults in the UK aged between 20 and 34 years lived with a parent or parents—26% of this age group (ONS, 2014).
This extended rearing partly reflects a human baby's relative immaturity at birth, even compared to its nearest animal relatives. At birth, a human's brain is nearly twice the size of a chimpanzee neonates', after adjusting for maternal size. However, a human newborn's brain is only about 25–30% of the adult's size. If humans were born with the same brain and behavioural maturity as a chimpanzee, gestation would need to last between 18 and 21 months. At this stage, the mother's upright posture would make pelvic birth impossible and the fetus' metabolic demands would probably mean that the mother would starve to death before giving birth (Hood, 2014).
At birth, a baby has almost all the 86 billion neurones an adult has, although connections are immature (Lagercrantz and Changeux, 2009; Hood, 2014). The pace of brain development is staggering: about 40 000 neuronal connections form each second during the first year of life—more than three billion a day. Within a year, a child's brain is about three-quarters of the adult's size (Hood, 2014). This rapid development probably accounts for the sometimes life-long impact of early experiences.
Tuning in to mum
Newborn babies rely on their mothers for protection, warmth and sustenance. Therefore, psychologist Bruce Hood (2014: 74) notes, ‘just about every capability of the newborn's senses seems to be tuned in to their mum's’. Babies very quickly learn to recognise their mother's face and prefer their mother's voice to that of other women (Hood, 2014). Even piglets recognise recordings of their mother's nursing calls (Okabe et al, 2012).
Indeed, a strong bond between infant and parents is critical for normal development. John Bowlby, a British psychiatrist, noted that many children separated from their parents during the Second World War and raised in institutions ‘grew up into socially impaired and delinquent teenagers’ despite being well cared for (Hood, 2014: 109). However, Bowlby suggested that these children missed a ‘critical’ stage in their development called attachment, which is an ‘evolutionary adaptive strategy to form a secure, nurturing bond between the mother and her infant’ (Hood, 2014). Bath time can be a richer sensory experience for a baby than other times of the day—not least because there is a variety of stimuli and the baby is naked so receives sensory stimulation over more of its body.
The mutually reinforcing stimulation of several senses is especially important as a newborn's visual acuity is only about 1/40th of an adult's. Babies can, however, still process complex visual information. For example, newborns prefer ‘attractive faces’ and are already ‘sensitive’ to the presence of eyes and eye contact (Lagercrantz and Changeux, 2009). Nevertheless, newborns need to rely on other senses more than adults. Bath time is a rich sensory environment filled with tactile sensations, noises and odours.
Don't dismiss scent
Biologists typically state that a dog's sense of smell is about a thousand times more sensitive than humans: dogs have approximately 220 million olfactory receptors, compared to 5–6 million in humans (Fox, 1997; Correa, 2011). Nevertheless, olfaction is, arguably, human's most underestimated sense. Humans can detect less than one part of certain substances in several billion parts of air (Fox, 1997) and, Porter (2004: 1562) notes, it is ‘becoming increasingly apparent that olfactory cues can exert a subtle but meaningful influence on human behaviour and physiology’.
The sense of smell develops early. Furthermore, an infant's olfactory system is highly plastic allowing children to develop preferences for a range of natural and artificial odours (Sullivan, 2000). Lagercrantz and Changeux (2009) suggest that a baby can probably smell from about the 20th week of gestation, when the epithelial nasal plugs disappear. Certainly, newborns detect and respond to ‘biologically relevant’ odours within minutes of birth (Porter, 2004). This ability to detect odours increases dramatically over the first 2 days of life (Sullivan, 2000) and infants seem to innately prefer certain odours.
Typically, for example, newborn infants prefer the odour of amniotic fluid to other smells (Lagercrantz and Changeux, 2009), but soon learn their mother's odour. In one experiment, researchers washed a breast of each mother immediately after birth. They placed 30 newborn babies between their respective mother's breasts and of these 30 babies, 22 spontaneously selected the unwashed breast (Fox, 1997). Babies begin to move their head towards the mother's odour within the first week of life (Porter, 2004). Recognising the mother's smell might be one of the first stages of attachment (Porter, 2004), and allows the infant to identify a source of nutrition.
Odours also appear to influence behaviour and emotions. For example, the smell of amniotic fluid and the mother's odour tend to have a soothing effect on newborns (Lagercrantz and Changeux, 2009). The odour of amniotic fluid has a soothing effect on infants possibly because they have an olfactory memory of the womb's scent (Porter, 2004). Familiarity with an odour seems to be central to an aroma's soothing effect: a familiar artificial odour reduced crying during venipuncture (Porter, 2004).
Furthermore, infants may show specific facial responses to pleasant and unpleasant odours just 3 days after birth, which seem to be very similar to expressions in adults (Sullivan, 2000). Babies seem to find some odours—such as vanilla, lavender and banana—inherently pleasant. Indeed, the smell of lavender may reduce levels of the stress-hormone corticosterone in infants (Sullivan, 2000). This suggests that the odours of bathtime—the smell of the water, the parents and the room—could contribute to bonding as well as making the experience enjoyable for baby, siblings and parents.
Against this background, increasing evidence suggests that odours support learning and memory, partly because olfactory pathways are anatomically unique among the senses. Most sensory systems pass through the thalamus, which evaluates sensory information and passes the input to the appropriate part of the cortex. In contrast, information about odours goes directly to the limbic system; a part of the brain involved with emotion and memory (Sullivan et al, 2015).
Long-term memories disappear during early childhood—so-called infant amnesia. Nevertheless, newborn infants recall sounds, melodies and rhymic poems they heard in the womb: although working memory is not fully efficient before 7 months (Lagercrantz and Changeux, 2009). Olfaction's unique anatomical pathway means that smell has ‘a unique and potent power to influence mood, acquisition of new information, and use of information in many different contexts including social interactions’ (Sullivan et al, 2015: 1).
A touching story
Tactile stimulation influences development across mammalian species. In humans, for example, tactile stimulation improves a child's growth as well as their motor, cognitive and social development (Pelaez-Nogueras et al, 1996). One landmark study enrolled 10 infants aged between 1.5 and 3.5 months at the start of the investigation. Adult carers alternated three 2-minute ‘touch’ and ‘no-touch’ sessions. During no-touch sessions, adults smiled and cooed at the child for as long as the infant maintained eye contact during the 2 minutes. During the touch session, adults smiled, cooed and rubbed the infants’ legs and feet during eye contact. As the infant could end the stimulation by breaking eye contact, the method allows researchers to easily compare the child's preferences for social stimuli (Pelaez-Nogueras et al, 1996).
Infants maintained eye contact for a mean time of 80.9% during the first 10 touch sessions compared to 53.4% when the adult just smiled and cooed. Mean time spent vocalising and smiling was 48.6 and 16.2%, respectively in the 10 sessions. In both cases, mean eye contact time increased with additional touch sessions. Conversely, children spent means of 3.0 and 24.0% in the touch and control sessions, respectively, crying and protesting (Pelaez-Nogueras et al, 1996).
Numerous studies from several species show the developmental importance of tactile stimulation. In rodents, maternal tactile stimuli—such as licking and grooming—enhance pups’ brain development. Maternal tactile stimuli can induce long-term changes, such as reducing stress responses when the pup reaches adulthood. In contrast, pups deprived of tactile stimulation show increased anxiety and depression responses as well as impaired memory and learning as adults (Okabe et al, 2012). Given that these processes seem fundamental to mammalian physiology, it seems reasonable to suppose the same applies to humans.
Against this background, multimodal stimulation—stimulating several sensory systems—is important for a child's development (Sullivan, 2000). Bathtime offers the ideal opportunity for multimodal stimulation, including the noise of the parents and the water, the odours and the various tactile stimulants, such as the feeling of water, wash cloth and the bath.
The need for education
Parents innately invest significant time bathing their children. A survey of 3574 parents of children aged 0 to 3 years from seven countries, sponsored by Johnson's Baby, found that in the UK bath time lasted on average 26.2 minutes and a child has, on average, 4.5 baths a week. In common with all surveys, these results might be subject to selection bias: parents who are most willing and able to spend time bathing their newborn might also be the most likely to complete a survey about bath time habits.
Nevertheless, midwives might need to educate new parents about the importance of bath time. The survey found that 89% of patients across the seven countries regard bath time as a ‘special activity’. However, only 55% of parents recognised that bath time was a ‘good bonding experience’ and just 23% appreciated that ‘baby massage is extremely important to their child's brain development’. Fourteen percent said that baby massage was not at all important.
In addition, midwives may need to stress the importance of ‘multimodal stimulation’ to parents. Bath time should be relaxing and fun for infants and parents. Bath time also helps parents establish a routine that helps encourage good sleep and help foster strong bonds between infants and carers. Bath time also provides an ideal opportunity for a parent to look for any changes in the skin, such as a rash. In addition, a growing body of evidence suggests that bath time provides the rich sensory experience that improves memory and other elements of cognitive development. Bath time is much more than good clean fun.