Why Do Babies Smile In Their Sleep: Reflex or Vivid Dreams?

Have you ever watched a sleeping baby suddenly break into a gentle grin and wondered what's behind that adorable smile? The vision of an infant's sleepy smile is a magical moment that often melts hearts. It's a subject that's fascinated scientists and parents alike. This mystifying behavior raises the question: Why do babies smile in their sleep? 

Throughout the years, researchers have delved into the depths of REM cycles, neonatal development, and infant expressions, unearthing theories that range from simple reflex actions to the potential of newborn dreams. 

While the great baby smile debate presses on: (reflexive smile or baby dreaming?!) We'll look at the connection of sleepy smiles  to infant sleep patterns, emotional development, and the parent-child bond, all woven into the fabric of pediatric sleep science.

Understanding Baby Sleep Cycles

People have two different types of sleep. The first type of sleep is known as non-rapid eye movement (NREM). The NREM phase of sleep whas four stages with varying brain waves, eye movements, and muscle movements. Non-REM sleep is considered deeper sleep and where adults spend more of the time sleeping. 

The other sleep type is known as rapid eye movement (REM). The REM stage is also known as “active sleep” and where babies spend the majority of their sleep. 

During REM, newborns are known to exhibit more smiles, with their muscles relaxing and brain activity increasing. It's why babies often move a ton while sleeping.

This stage is essential for their overall growth, with studies indicating that it supports memory consolidation, brain maturation, and learning. Therefore, those fleeting grins of slumbering infants carry more weight than mere expressions; they are a window into their neonatal development and the critical processes occurring as they rest.

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The Reflex Smile

If you've ever watched a sleeping baby, you've likely seen the involuntary movements, with one of the most precious being the curvature of their lips while sleeping. These are commonly referred to as reflex smiles and are one of the cutest newborn sights delighting parents for ages.

Unlike the intentional and communicative social smile, reflexing smiling does not result from a positive social interaction or happy emotions. 

Instead, it is an instinctive motion of the facial muscles, like the grasp of a hand or the blink of an eye, emerging most frequently during the REM stage of sleep. This stage of light sleep stimulates many automatic responses, facial expressions which include these subconscious first smiles. 

Emotional Growth and Dreams

Observing a baby's first smile while sleeping, may peak some interest around the ongoing debate: do infants experience dreams that induce these sleep smiles?

Scientists suggest that even if babies dream, their slumber visions are likely to be quite different from adult ones, lacking narrative or structure due to their developing brains. 

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Yet, these spontaneous smiles may still be tied to positive emotional developments occurring during sleep. As a sweet smile lights up a baby's face, they offer us a glimpse into a world we are yet to fully comprehend, encapsulating the beauty and complexity of growth, even in the serenity of sleep.

Common Misconceptions About Baby Smiles

The biggest debate around the smile of a baby in those early weeks is whether or not it's a real smile or a just responsive smiles during certain stages of sleep?

While a new parent (myself included) cherish the sight of a baby smiling in sleep, and various myths swirl around these sleepy grins, the truth is, these smiles are likely not a result of the baby's happiness or reactions to pleasant dreams, similar to adults.

 

On the flip side, another common belief is that all smiles during sleep are reflexive and don't indicate any underlying positive emotions. In contrast, researchers find that even reflexive smiles can be part of early emotional development and neuronal maturation.

In other words: babies smiles are real, and not always reflexive. But they may not be occurring for the reasons we think as babies brain maturity is vastly different than adults, or even older children.

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How to distinguish early smiles: Observation Tips for Parents

Learning the different types of smiles your baby makes can deepen your connection and understanding with your little one.

• Choose Optimal Observation Times: Observe when your baby naturally transitions between sleep stages, typically right before waking or during mid-nap sessions.
• Maintain a Soothing Environment: Keep the room dimly lit and quiet to avoid waking your baby during observation periods.
• Keep a Sleep Diary: Record your baby's sleep patterns and any smiling occurrences to identify trends and share with pediatricians if needed.
• Limit Physical Interactions: Refrain from touching or moving your baby while they sleep to ensure natural sleep behaviors are observed.
• Use Baby Monitors Smartly: Employ audio or video monitors that allow you to watch your baby's expressions without being physically present in the room.
• Understand Normal Sleep Behaviors: Educate yourself on typical infant sleep stages and expressions to differentiate between normal movements and smiles.
• Appreciate the Moments: Use the observation time to bond emotionally with your baby, recognizing smiles as a delightful aspect of their growth and happiness.

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What Smiling in Sleep Could Indicate

Newborn smiles during sleep often intrigue parents, sparking curiosity about their meaning. 

Subconscious smiles, particularly those occurring during REM cycles, may signal a healthy development stage and contentment. While reflexive in nature, these grins can show that the baby's brain and neurological systems are maturing as expected. 

In contrast, ‘social smiles,' shared in response to human interaction, emerge later and signify emotional growth and the ability to connect with others. These adorable smiles are often intentional and as a result of meaningful moments.

Many researchers have pointed out that, in most instances, a sleeping baby's smile is simply a reflex and not a reaction to dreams or emotions. However, an absence or significant change in sleep-time smiling behavior may warrant pediatric attention to rule out any underlying issues. 

In rare cases, there is cause for concern around abnormal movements where babies grunt or squirm in an unusual way, which could indicate gelastic seizures and parents are should seek medical help from their healthcare providers as soon as possible if concerned.

Medical professionals historically suggest parents enjoy these precious moments but remain observant for new information or consistent patterns, which can offer clues to a baby's sensory experiences, emotional range, or if developmental milestones are not being met. Through attentive observation, parents can often distinguish between the variety of smiles and what they may indicate, hence facilitating early detection of developmental progress and potential concerns.

Wrapping Up the Smiley Journey

For parents, observing the serene grin of a slumbering infant serves as a joyful reminder of the pure simplicity in life's early stages. 

Newborn babies typically display these charming expressions during active REM sleep, suggesting a healthy and regular sleep cycle, crucial for development. 

Witnessing and cherishing these moments not only provides emotional fulfillment but also invites you to actively participate in the ever-evolving world of child development.

I encourage you to engage with your child's growth, recognize the reflexive nature of their smiles, and appreciate the silent yet profound connection it signifies. By remaining observant and nurturing, you contribute to their overall well-being and foster an environment brimming with love and security.

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Resources

1. Ednick M, Cohen AP, McPhail GL, Beebe D, Simakajornboon N, Amin RS. A review of the effects of sleep during the first year of life on cognitive, psychomotor, and temperament development. Sleep. 2009;32(11):1449-1458. doi:10.1093/sleep/32.11.1449
2. Chen, H. L., Gao, J. X., Chen, Y. N., Xie, J. F., Xie, Y. P., Spruyt, K., Lin, J. S., Shao, Y. F., & Hou, Y. P. (2022). Rapid eye movement sleep during early life: A comprehensive narrative review. International Journal of Environmental Research and Public Health, 19(20), 13101.https://pubmed.ncbi.nlm.nih.gov/36293678/
3. Kawakami, F., Tomonaga, M., & Suzuki, J. (2017). The first smile: Spontaneous smiles in newborn Japanese macaques (Macaca fuscata). Primates, 58(1), 93–101.https://pubmed.ncbi.nlm.nih.gov/27485748/
4. Challamel, M. J., Hartley, S., Debilly, G., Lahlou, S., & Franco, P. (2021). A video polysomnographic study of spontaneous smiling during sleep in newborns. Journal of Sleep Research, 30(3), Article e13129.https://pubmed.ncbi.nlm.nih.gov/32748500/
5. Cecchini, M., Baroni, E., Di Vito, C., & Lai, C. (2011). Smiling in newborns during communicative wake and active sleep. Infant Behavior & Development, 34(3), 417–423.https://pubmed.ncbi.nlm.nih.gov/21524798/
6. Kurjak A, Azumendi G, Vecek N, et al. Fetal hand movements and facial expression in normal pregnancy studied by four-dimensional sonography. J Perinat Med. 2003;31(6):496-508. doi:10.1515/JPM.2003.076
7. Forestell CA. Flavor Perception and Preference Development in Human Infants. Ann Nutr Metab. 2017;70 Suppl 3:17-25. doi:10.1159/000478759
8. Clé, M., Maranci, J. B., Weyn Banningh, S., Lanfranchi, J., Vidailhet, M., & Arnulf, I. (2019). Smiling asleep: A study of happy emotional expressions during adult sleep. Journal of Sleep Research, 28(4), Article e12814.https://pubmed.ncbi.nlm.nih.gov/30614101/
9. Shellhaas, R. (2022, October 28). Overview of infantile epilepsy syndromes. In D. R. Nordli & J. A. Garcia-Prats (Eds.). UpToDate., Retrieved December 8, 2022, fromhttps://www.uptodate.com/contents/overview-of-infantile-epilepsy-syndromes
10. Tapia, I. E. & Wise, M. S. (2022, April 13). In R. D. Chervin (Ed.). UpToDate.https://www.uptodate.com/contents/sleep-physiology-in-children
11. Jian, N., & Teti, D. M. (2016). Emotional availability at bedtime, infant temperament, and infant sleep development from one to six months. Sleep Medicine, 23, 49–58.https://pubmed.ncbi.nlm.nih.gov/27692276/
12. Messinger D, Fogel A. The interactive development of social smiling. Adv Child Dev Behav. 2007;35:327-366. doi:10.1016/b978-0-12-009735-7.50014-1
13. Barrett, L. F., Adolphs, R., Marsella, S., Martinez, A. M., & Pollak, S. D. (2019). Emotional expressions reconsidered: Challenges to inferring emotion from human facial movements. Psychological Science in the Public Interest, 20(1), 1–68.https://pubmed.ncbi.nlm.nih.gov/31313636/
14. Malik, F. & Marwaha, R. (2022, September 18). Developmental stages of social emotional development in children. In StatPearls. StatPearls Publishing., Retrieved December 8, 2022, fromhttps://www.ncbi.nlm.nih.gov/books/NBK534819/
15. Uribe-San-Martin, R., Ciampi, E., Lawson-Peralta, B., Acevedo-Gallinato, K., Torrealba-Marchant, G., Campos-Puebla, M., & Godoy-Fernández, J. (2015). Gelastic epilepsy: Beyond hypothalamic hamartomas. Epilepsy & Behavior Case Reports, 4, 70–73.https://pubmed.ncbi.nlm.nih.gov/27195219
16. Téllez-Zenteno JF, Serrano-Almeida C, Moien-Afshari F. Gelastic seizures associated with hypothalamic hamartomas. An update in the clinical presentation, diagnosis and treatment. Neuropsychiatr Dis Treat. 2008;4(6):1021-1031. doi:10.2147/ndt.s2173
17. Kerrigan, J. F. & Iyengar, S. (2017, March 3). Gelastic and dacrystic seizures. Epilepsy Foundation.https://www.epilepsy.com/what-is-epilepsy/seizure-types/gelastic-and-dacrystic-seizures
18. Beltre, G. & Mendez, M. D. (2022, September 18). Child development. In StatPearls. StatPearls Publishing., Retrieved December 8, 2022, fromhttps://www.ncbi.nlm.nih.gov/books/NBK564386/
19. Phillips, M. L., Schmithorst, V. J., Banihashemi, L., Taylor, M., Samolyk, A., Northrup, J. B., English, G. E., Versace, A., Stiffler, R. S., Aslam, H. A., Bonar, L., Panigrahy, A., & Hipwell, A. E. (2021). Patterns of infant amygdala connectivity mediate the impact of high caregiver affect on reducing infant smiling: Discovery and replication. Biological Psychiatry, 90(5), 342–352.https://pubmed.ncbi.nlm.nih.gov/34130856/