Baby sleep and the problem of spurious correlation

So if you have a newborn or even an older baby who does not sleep well you should mentally prepare yourself for an avalanche of advice from well meaning people who are only going to frustrate you.

They will tell you: All you need to do to get that baby to sleep is X.

 "X" is going to vary depending on who the person is you are talking to. But X is almost always something you have tried 100 times with no success, and it tends to be things like:

1. swaddling
2. rocking/walking to sleep
3. white noise
4. night light
5. co-sleeping
6. feed baby more before bedtime (the older generation will tell you to put rice cereal in the bottle)
7. pacifier/no pacifier
8. letting baby fall asleep on your stomach

These people could be anyone: your mother-in-law, best friend, distant cousin, neighbor, check-out lady at the grocery store, etc. When I was looking for a day care provider for my son one woman I met listened to me talking about how he has trouble falling to sleep and then after a dramatic pause she told me that the secret to getting babies to sleep was putting the radio on to play static and that this worked like a charm for all four of her children. The best part was the way she revealed this secret to me as though it was the holy grail. Needless to say I was not super impressed by her and found a much better day care provider somewhere else.

In order to respond to these people in your sleep deprived state of constant frustration you might want to practice nodding your head and saying "Oh really? Thanks so much for the good advice. I will definitely try that." If you are a truly sarcastic person then you can even add, "Wow, I've never heard of that idea before! I'm so glad I talked to you!"

Warning: this post represents my personal opinion and I should re-state what I believe is the cardinal rule of babies: Every baby is different. That said maybe some babies do transform from bad sleepers to good sleepers after doing something simple like swaddling them. I think it is always worth trying new things and taking advice from more experienced parents, but if following their advice is not working, then keep reading this post.

Here is the problem, all these people are assuming that the reason their babies slept like little angels is because of X (their intervention of choice). In my not so professional opinion babies sleep well for one of three reasons:

1. disposition - in other words you got lucky and gave birth to a baby who is a better sleeper and is better at "self soothing" from the get go
2. age - all babies gradually get better at sleeping as they age and learn the difference between night and day and eventually learn how to soothe themselves to sleep 
3. training/learning - some babies can become better sleepers earlier and faster if you do some consistent sleep training (although this should never be done during the newborn period)

If you have a newborn (0-3 months) the reason they are sleeping well is probably neither age nor training because they are too young for these to be causes. The reason they are sleeping well is that you baby was destined to be a better sleeper. Not sure what other mamas experienced, but I should have known from the first night with my son in the hospital that we were in for a very bumpy road as far as sleeping was concerned.

So why do all these well-intentioned people honestly believe that X is the secret to success? 

In statistics this phenomenon is called spurious correlation. The idea is that everything has a cause and effect, but sometimes we erroneously think the cause is B, when in fact it is actually A.

Example:
We notice that when people eat a lot of ice-cream (B) there seems to be a lot of riots/street violence (C) and we assume an increase in the eating of ice cream causes an increase in riots.  (example courtesy of Professor David Phillips)

What is really happening? There is a third variable that we are failing to consider: summer time. When it is hot people eat more ice cream. When it is hot and students are out of school and the days are longer people are more likely to riot.

So we think B causes C (ice cream causes riots), but in reality A causes B and A causes C (summer time causes an increase in both ice cream consumption and riots).

Okay seems like a sort of silly example and the cynical reader will be thinking that anyone with a brain knows that ice cream does not cause riots. Correct, cynical reader. So lets give one more quick example.

It is commonly assumed that exercise (B) causes people to be healthier (C). Is this true? Maybe not. There is a third variable (A) health. Confused yet? Health can be both a cause and effect. It works like this. If you are healthier to begin with, then you are more likely to have the time and energy for exercise. So being healthier causes you to exercise more. Being healthy early in your life causes your to be healthy later in your life. Real life is full of confusing and messy examples of spurious correlation and knowing about this phenomenon might make you think differently about the world. For example is it intelligence and hard work that leads people to succeed in life? This is the meritocracy argument. Or could there be other factors that lead people to succeed (i.e. socioeconomic status, education, cultural background, circumstances). For an interesting and easy to read analysis of this issue read Malcolm Gladwell's Outliers.

So let's get back to baby sleep. Your mother-in-law/friend/cousin tells you that swaddling (B) causes her baby to sleep like an angel (C). So there is some correlation between swaddling and sleeping happily. I am arguing that in most cases it is the babies disposition (A) that is causing them to sleep like an angel (C).

At my son's 2 month doctor appointment when our doctor was explaining to us how our son fit the typical description of "colic" he told us about the latest theory of what causes colic. Colic basically occurs when a baby's brain has not developed enough to "self soothe". In other words babies are not born knowing how to calm themselves down. Just like adults babies wake up many times during the night. However as adults we do not even realize that we wake up and we generally just slip back into a deeper sleep. Most newborns will cry and rely on parents to help them get back to sleep. Like adults, babies fall on a spectrum and some are just born with less of the type of brain development that allows them to soothe themselves back to sleep once they wake up. One reason I am convinced that this theory makes sense is the fact that colicky babies seem to need the same high level of parental intervention during the day and non-sleeping hours (as opposed to what my good friend calls "plop down babies").

We may never understand exactly why some babies adjust to sleeping better or earlier than others but if you understand the logic of spurious correlation at the very least you should now know not to blame yourself if your baby is having trouble sleeping. Those mamas with the happily sleeping babies are not better parents than you. It may even be the case that some of those parents will come to you for advice when they have their second or third child and suddenly they are doing all the same things they did with the first kid, but this baby won't sleep. So when they come to you for advice and they are totally miserable from sleep deprivation you have two choices. You can tell them "All you need to do is X and your baby will sleep like an angel", or you can tell them the truth. I know what I would do :)