Some self-appointed experts have taken a dangerously dim view of newborn babies.
Until the late 20th century, many medical authorities actually denied that newborns can feel pain (Rodkey and Ridell 2013).
Thankfully, modern science has debunked that notion, and shed light on the newborn senses.
What is it like to be a newborn? What do they notice about the world, and how does sensory information influence their development?
Here is an evidenced-based look at your baby's sense of touch, sight, sound, smell, and taste.
Babies experience touch long before they are born. As they wiggle and kick, they often touch themselves, events that may help their brains learn about the connection between touch and the internal sensations it causes.
Babies also experience touch from the outside. If a pregnant woman rubs her belly, her fetus can feel the vibrations (Marx and Nady 2015).
After birth, touch can have powerful effects. Experiments show that skin-to-skin contact can soothe newborns in pain, and help babies grow and thrive (Johnston et al 2017; Conde-Agudelo and Díaz-Rossello 2016).
Affectionate touch can also protect at-risk infants from developing abnormal stress response systems. It may change the way certain genes get expressed during development, making newborns less prone to emotional problems later in life (Murgatroyd et al 2015).
In studies tracking human infants over time, newborns who receive more stroking tend to show less emotional negativity as they get older, and fewer symptoms of anxiety and depression (Sharp et al 2012; Sharp et al 2015; Pickles et al 2017).
So cuddling your newborn isn't just natural, intuitive, and
humane -- the right thing to do. It's also a form of environmental programming,
one that increases your baby's chances of developing greater emotional health
What about the more investigative aspects of touch? The information that babies gather about their world when they feel textures, or grasp something in their fingers?
In fascinating experiments, Arlette Streri and her colleagues discovered that newborns are capable of inferring the appearance of an object from touch alone (Streri 2003; Streri and Gentaz 2004; Sann and Streri 2007; San and Streri 2008).
Experimenters gave each baby a simple object to handle: either a solid wooden cylinder, or a solid wooden prism with a triangular base. The babies touched only one type of object, and couldn't see what they were touching. Then came the test.
The newborns were shown both objects, only one of which they had previously encountered. Could the newborns tell the difference? Recognize the object they had held in their hands?
Remarkably, they could. And just as interesting, the babies couldn’t perform this trick in the other direction. If a baby was allowed only to look at a new object, he wasn't able to recognize it later by touch alone.
The results suggest that newborns use their sense of touch to help them interpret visual information. When a baby touches your face, he's learning how to recognize it visually.
But that doesn't mean that your newborn senses the world primarily through touch, or that she prefers to communicate through touch alone. On the contrary, when it comes to social interactions, babies seem to find touch more reassuring if it comes as part of a package -- one that includes affectionate cuddles, friendly eye contact, talking, and rocking.
In an experiment on newborns, researchers randomly assigned infants to one of two treatments. Half the babies were stroked by a silent, uncommunicative caregiver. The other half were also stroked, but in combination with rocking, eye contact, and soothing speech.
The babies who received the combination package experienced a drop in stress hormone levels. The babies who were stroked in isolation experienced a stress hormone surge (White-Traut et al 2009).
And babies can also get stressed when we're too pushy -- when we ignore their desire for downtime, touching and stimulating them in ways they don't want (Feldman et al 2010). So the key is to pay attention to your baby's signals, and provide him with the sort of touching that he finds enjoyable or soothing.
For more information, see these tips on reducing stress in babies.
You've probably heard that newborns can't see very well, and it's true.
Babies are born without true depth perception, and color vision is very limited. Stereoscopic depth perception doesn't appear until approximately 16 weeks postpartum (Streri et al 2012; Held et al 1980). Color discrimination is very poor immediately after birth, and develops gradually over a period of months (Johnson 2010).
For instance, when researchers tested 4-day old infants, they found these babies could successfully distinguish between white and orange (light with a wavelength of 595 nm).
But they failed to distinguish white from yellow-green colors (Adams et al 1991). Newborns also have trouble with dark blue (wavelength 450nm, Adams 1995).
At 3 weeks, some babies have shown the ability to distinguish red from green (Clavadetscher et al 1988). But four-week-old babies typically have difficulty distinguishing red from yellow. Their experience of red is probably quite different from that of an adult with normal color vision.
By 8 weeks, most babies possess better color perception. This is the age by which they can reliably distinguish the color red (wavelength 633 nm) from white, as well as turquoise blue (486 nm), and some blue-greens (496-516 nm). But they still struggle with yellow and yellow-greens, as well as certain shades of purple (see Banks and Bennet 1988 for summary). Color abilities continue to develop throughout infancy and early childhood (Goulart et al 2008).
This isn't colorless vision. Contrary to the popular claim, newborns don't see the world in black and white. But it's a world with very little color, and more subtle contrast between hues.
Then there is the question of visual acuity: How blurry to things look? Newborn vision is so fuzzy, it easily meets the threshold for being legally blind.
To get a feeling for the difference, imagine a pattern of black-and-white stripes on a piece of paper. The stripes are just wide enough that you can fit two alternations -- black/white/black/white -- per centimeter.
The striped paper is placed against a solid, grey backdrop. You stand back a few feet and take a look. Can you still see the stripes, or do they disappear -- blend imperceptibly into the background?
If you have normal vision, you will have no difficulty seeing the stripes. But the average newborn won't be able to detect the stripes, not even if you hold the display 15 inches from her face.
To the baby,
the stripe pattern is too fine. The stripes blur together (Cavallini et al
2002). An optometrist would rate her visual acuity at around 20/640.
So newborns see much less than we do. But that doesn't stop babies from seeking out visual information. Newborns are fascinated by the things they can see.
Like the T. rex in Jurassic Park, newborns find moving objects to be especially interesting (Valenza et al 2015). They also show a special attraction to faces, and they can rapidly learn to recognize the faces of their caregivers.
In one study, researchers presented babies with video playbacks of two faces. One was the infant's own mother. The other was the face of an unfamiliar woman (Bushnell et al 1989).
The infants—who ranged between 12 and 36 hours old—showed a clear preference for watching their mother's face, as opposed to the face of the stranger. And this was true despite the fact that the faces were presented in silence, and without any olfactory cues. The babies couldn't have been tipped off by their mother's voice or scent.
Other studies have replicated these results, and offer insight into the visual clues that babies use to tell people apart: They are probably noticing differences in face shape, hairstyle, and color (Pascalis et al 1994).
Babies develop the ability to hear long before they are born. In fact, they've listened so long, they aren't just familiar with the sound of their mothers' voices. They can pick out some of the distinctive patterns of their mother's native language, and they may even mimic these patterns when they cry!
In a study of French and German babies, researchers found that French newborns produced cries with a rising melodic contour, much the way French speakers do when they utter a sentence. The German babies, by contrast, produced typically Germanic-sounding cries -- with a falling intonation (Mampe et al 2009).
As far as we know, there is nothing inferior about a newborn's sense of smell, and odors are an important part of the baby's world. Experiments indicate that newborns are actually better at detecting the odor components in human sweat than adults are (Loos et al 2017).
Experiments also show that newborns recognize the smell of amniotic fluid (Varendi et al 1997), and they like the scent of breast milk.
When researchers presented formula-fed newborns with two different odors -- the scent of breast milk from an unfamiliar woman, and the scent of a familiar infant formula -- the babies showed a preference for the odor of human milk (Marlier and Schaal 2005).
Other studies indicate the scent of breast milk appears to have a calming, painkilling effect on newborns (Baudesson de Chanville et al 2017; Neshat et al 2016; Nishitani et al 2009).
And if you familiarize newborns to an odor shortly after birth, they can develop a fondness for it. In one experiment, newborns were introduced to the scent of chamomile while they were nursing. Days later, their attraction to the scent of chamomile was as strong as their attraction to the scent of breast milk (Delaunay-El Allam et al 2006). Similar results have been reported for the scent of vanilla (Goubet et al 2007).
What about identifying individuals? Can newborns recognize caregivers on the basis of odor alone?
It seems that they can. In one breast milk study, newborns undergoing a painful procedure (a heel prick) were soothed by the smell of milk. But only if the milk came from their own mothers (Nishitani et al 2009).
In another study, newborns were presented with the odors of different breast milk samples--samples donated by their mothers and by other, unfamiliar women. The babies mouthed more in response to their own mothers' odors, and the amount of prior exposure made a difference. Those who'd experienced more than 50 minutes of contact showed a greater difference in mouthing (Mizuno at al 2004).
And what about the newborn sense of taste?
As every foodie knows, our experience of flavor is
influenced by our sense of smell. For example, differences in odor account for
much of what makes an apricot taste different than a peach.
But of course it isn't only about odor. We also have taste buds, and these help us detect at least five dimensions -- sweetness, saltiness, bitterness, sourness, and umami (a savory, hearty taste associated with glutamate, and found in meats, milk products, and mushrooms).
A newborn senses all of these dimensions except one: Experiments suggest that babies can't taste salt until they are about 4 months old (Beauchamp et al 1986).
As for the rest, newborns are especially partial to sweetness. In fact, when babies are given a sugar solution immediately before a painful procedure--like a heel prick--they cry less. Newborns also seem to like the taste of glutamate, which is found in breast milk (Beauchamp and Pearson 1991).
By contrast, newborns react negatively to some (but not all) bitter substances. And when a newborn senses a sour substance, he is likely to pull away and grimace (Steiner 1977).
Does the sense of taste have any practical consequences for a newborn? You might not think it matters much, since young infants consume only breast milk of baby formula. But experiments indicate that the flavors in a mother's diet get passed along in the breast milk, and the babies notice.
Early exposure to these "added" flavors may help babies develop preferences for healthful foods later on. You can read more it here.
Immediately after birth, babies show remarkable social abilities. For more information, see this evidence-based review of how a newborn senses the social world.
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Content of "The newborn senses: What can your baby feel, see, hear, smell, and taste?" last modified 8/17
Image credits for the Newborn Senses:
Title image of sleeping newborn by Joshua Rappeneker / flickr
Image of baby cooing over mother's shoulder by Niko Knigge /flickr
Image of baby with one eye open by Christine Szeto flickr
Image of blurry woman by Shannon Kringen / flickr
Image of ginger-haired newborn by photosavvy / flickr
Image of mother and newborn by Harald Groven / flickr
Small portions of this article are derived from an earlier work by the same author, "Wired for fast track learning? The newborn senses of taste and smell" (2011).