Sleep probability charts

Isaac at six months:

Laurel at six months:

Comparing these two sleep probability charts shows us that Laurel indeed slept longer at six months than Isaac did at the same age. Both kids were likely to be asleep at 8:30 p.m., but Isaac was likely to wake up at 6:30 a.m. while Laurel slept a whole hour later. Both kids had night wakings scattered randomly throughout the night, but I expect that Laurel's seven-month sleep probability chart will have fewer of them.

More than that, the charts reveals that Laurel had a more regular nap schedule. In Isaac's chart, that big light gray blur in the morning means that there was a 50% probability that he might have been asleep at any given time from 8:00 a.m. to 11:00 a.m., even though his morning nap only lasted 45 measly minutes. Meanwhile, his afternoon nap was completely unpredictable.

Laurel, on the other hand, had a morning nap represented by a tighter and darker stripe from 9:30 a.m. to 11:00 a.m. Her sleep patterns are easier to predict. Isaac didn't get that regular until he was eight months old.

If you want to see more probability charts, look right above these two charts and click on the links from the kids' names. It's interesting to see how things change over time: how newborn sleep runs on a 24-hour clock, how two naps consolidate into one, and how that one nap gradually vanishes completely. This is the legend, which uses a grayscale ranging from white to black to represent the probability of the child being asleep at any given time:


And, just for fun, here's what Isaac has been doing lately: this is his sleep probability chart from last month. Looking good, isn't it? Well, that paler stripe in the middle of the night represents the brief waking moment when he gets out of his bed and comes into his parents' bed.

Isaac at 46 months: