Babies are better at holding their breath underwater than you are. They have a stronger dive reflex, which helps them hold their breath quickly when submerged. So what does that mean for their underwater abilities?
Babies are undeniably delicate and fragile. They come out after 9 months of gestation with large misshapen heads with necks too weak to support them, along with tiny limbs and very little hand-eye coordination. It is ludicrous to even suggest that a newborn baby, who can’t even sit upright on its own, would instinctively know what to do when placed in a swimming pool.
However, interestingly enough, the opposite is true. In fact, you can see evidence of this quite clearly. If you’ve ever blown air directly at a baby’s face, you may have noticed that they react in a funny way. They stop whatever they’re doing, pause for a moment, as if buffering, close their eyes, suck in a lot of air, and then hold their breath. Many parents, to their advantage, discover this unique behavior. Nifty parents will blow air in their baby’s face to stop the baby from crying.
As you might expect, there’s more to this reaction than meets the eye.
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What Is The Mammalian Dive Reflex?
A baby’s reaction to the blowing of air into their faces is actually a reflex known as the bradycardic reflex or the mammalian diving reflex. The mammalian dive reflex refers to a set of physiological responses that occur in mammals (including humans) when they are submerged in water. This reflex is especially strong in infants and young children, allowing them to hold their breath longer and conserve oxygen while underwater.
The dive reflex was first described by a British doctor, Edmund Goodwyn, in 1786, but it was Paul Bert’s publication in 1870 that actually identified the physical changes that help mammals conserve oxygen when they’re immersed in water. Bert, who was a zoologist, actually observed the reflex first when studying forced immersion in ducks.
When you hold your breath and go underwater, your face and nose become wet, which triggers three main changes in your body: your heart rate slows down, you stop breathing temporarily, and the blood vessels in your body’s extremities narrow. These changes are all part of what’s called the diving reflex.
The slowing of the heart rate is important because it reduces the amount of oxygen the body requires to function. By stopping breathing, the body is able to conserve whatever oxygen it already has. The narrowing of the blood vessels in the extremities helps to shift blood flow toward vital organs, such as the heart and brain, which need oxygen to function properly. All of these changes are part of the diving reflex.
Studies have shown that babies and young children have stronger dive reflexes than adults, which is intuitively strange, as there’s no reason a baby would ever simply go for a swim. Scientists aren’t certain why babies have a stronger dive reflex, but some experts have suggested that this behavior is an evolutionary adaptation designed to help protect infants from drowning. Others have proposed that it is simply a reflexive response to the sudden change in environment.
This reflex also helps to explain why some individuals are able to hold their breath underwater for much longer periods of time than others.
So, Can Babies Swim?
Remember when we first asked whether babies would be better suited to swimming than sitting upright?
It should be noted that even though babies have a strong dive reflex, it doesn’t mean they’re ready to swim just yet. In recent years, research has been severely misinterpreted and used in the public sphere to encourage and sway new parents into baby swimming classes.
Although babies do exhibit all the required reflexes to effectively hold their breath underwater, this doesn’t mean they’re all Michael Phelps just yet. In fact, scientists actively recommend not triggering the dive reflex too often in children, especially infants and toddlers, as it can sometimes contribute to sudden infant death syndrome or SIDS. When babies display a hyperactive tendency for the dive reflex, they usually also develop an increased tendency for bradycardia or apnea.
Do Adults Retain Their Dive Reflex?
For as long as you live, you will retain your dive reflex.
As humans age, the dive reflex is still present, but the response from just wetting or cooling the face is not as intense. Where adults and babies differ is in the fact that babies have more of a full-fledged overreaction of a reflex, as opposed to adults, who have a more scenario-specific dive reflex. To fully elicit a dive reflex from adult humans, one must hold their breath and completely immerse their face or body in water.
The full effect of the dive response in adults requires the combination of facial stimulation and breath holding. Despite the changes in the reflex as humans age, the physiologic changes observed while submerged in water remain observable throughout life.
However, if you want to elicit the same reaction from a baby, you don’t even need water. In fact, they don’t even need to hold their breath. So much as a strong gust of wind aimed directly at their face is enough for them to prepare for a dive!
References (click to expand)
- Matturri, L. (2005, January 1). Sudden infant death triggered by dive reflex. Journal of Clinical Pathology. BMJ.
- Godek D, Freeman AM. Physiology, Diving Reflex. [Updated 2022 Sep 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK538245/
- Panneton, W. M., & Gan, Q. (2020, June 5). The Mammalian Diving Response: Inroads to Its Neural Control. Frontiers in Neuroscience. Frontiers Media SA.
- The Mammalian Diving Reflex - Sites at Dartmouth. Dartmouth College