This is probably going to be one of several caveats I'll include on this blog, and probably the earlier the better. First off, you'll notice that generally the way that I'll be discussing theory, research findings, recommendations and cautionary notes seems to treat children as if they were all the same. Yes, the premise of our book is that children go through normative stages at predictable ages. Obviously, we could not make these predictions if we were thinking about the individual child’s personality. But both as a developmentalist and as a parent (and especially as a parent of twins!) I am fully aware of how different children can be. Individual differences take many forms and result from many causes. They can result from the influence of parents and siblings, from environmental features of the home and the neighborhood, from health and dietary issues, traumatic events, and so on. But some individual differences are at least partially built into the child’s nervous system, generally through the action of genes that are responsible for constructing brains, glands, sense organs, and all the wiring that connects them. These variations, usually referred to as temperament by psychologists, are not always evident at birth. Sometimes a remarkably distinct temperamental feature won’t show itself until the middle or end of the first year, or even later. However, temperamental differences, by definition, are built in to the child’s biological make-up and so, as a rule, they do show up early in development.

I'll get into the way that developmental psychologists parse temperament in a later post. But right now I just wanted to put a placeholder on the point that, yes, kids are different and not all kids are going to conform to the general pattern of changes I'll outline, at the exact ages I'll specify. But GENERALLY, there's a large body of research (and when I figure out how to link to half of it, I will) that's documented that the majority of kids DO conform to the cognitive and emotional schedule I'll be discussing. That doesn't mean that this schedule will relate to SLEEP issues in the same way for all kids, but it does mean that most of you should recognize the cognitive and emotional changes that I'm talking about at around the same ages.  If you don't, TELL ME. These stages are meant as guidelines, not absolute deadlines. The more "data points" we have in terms of different children on different schedules, the better we will all be at understanding how development works.