Is she a good sleeper?”
It’s one question new moms and dads hear over and over again. We know that how well an infant sleeps is one of the primary determinants of how pleasant or exhausting the first few months are going to be for a new parent. All those hours spent sleeping are important for learning as well.
When do babies actually start sleeping in a predictable way? Research with premature infants shows that at 30-34 weeks gestation the human sleep-wake cycle becomes more rhythmic, sleep cycles become more predictable, and quiet sleep bouts increase in duration, corresponding with changes in the brain. Prior to the third trimester however, fetal sleep cycles are immature, disorganized and unpredictable. This doesn’t mean that newborns should sleep in a predictable way (let’s say at night, perhaps), but that we can observe a real difference between true restful sleep and active states by the third trimester.
Newborns spend up to 70% of their time asleep, about 16-18 hours per day, and wake for short periods of time. For the first two months of life, newborns wake about every 4-5 hours, and by three months of age they may sleep for 6-7 hours at night. Hey, that sounds like my baby should be sleeping through the night at 3 months! But we all know this just means you will be up at 2 am because he fell asleep at 7 pm.
When your baby is sleeping you might have observed two types of sleep; active sleep, which is when you can see variability in respiration and rapid eye movement, and quiet sleep, when respiration, heart rate and eye movements are slow and regular. Infants spend more time in active sleep than adults, but the time spent in active sleep decreases over the first year of life, along with a decrease in total sleep time. Babies shift to more quiet sleep than active sleep at the beginning of the night by their first birthday.
So with all that sleeping, and only brief periods of alert wakefulness, how do babies learn so much during that first year of life? The learning that occurs during brief periods of wakefulness is likely consolidated during long periods of sleep, similar to memory consolidation processes observed in adults. On top of that, research shows that infants not only can process information while they sleep but actually learn while they sleep.
For example, we know that infants can process auditory information while they sleep, based on very cool studies that showed differences in brain responses of sleeping babies while listening to their mother’s voice versus a stranger’s voice. Infants’ brain response to the stranger’s voice was characteristic of a brain response seen in adults when they experience something new; these babies were able to discriminate the voice of their mother from the new voice of a stranger – while sleeping.
Even more amazing is evidence of learning in sleeping babies. In one study, babies experienced a puff of air onto their eye (which made their eyelid move) paired simultaneously with a tone. Each time the tone was presented the infants’ eyelid moved due to the puff of air, a conditioned response. Eventually, infants moved their eyelid in response to the tone alone, with no puff of air, suggesting that they learned the conditioned response – while sleeping.
Babies need an extraordinary amount of sleep to continue the development that starts in the womb. Moreover, the unique characteristics of infant sleep patterns seem to be optimal for learning.
So, sleep baby sleep!
Developmental psychologist Jessica Beer combines her real world experience as a mother with her professional training as a researcher to provide parents with a practical way to apply the most current findings in childhood development research to their everyday life. Jessica is also a co-founder of The Urban Chalkboard playcafe, and welcomes questions and feedback from readers at [email protected]