R.J.
Kids don't develop uniformly.... but rather in stages. Think of a staircase instead of a ramp. It also helps to think of it as MULTIPLE staircases. If they are going up the cognitive staircase, the physical staircase is usually left alone. Then they hop off of the cognitive stairs for a mo' and work on the physical... then the emotional... then back to the physical... then 3 steps on cognitive. Then 2 steps on fine motor. Then, etc., etc., etc..
Hence why you'll almost NEVER find a child who hits all the milestones at the same place (early, dead on, late)... but the WAY in which they hit them makes a lot of sense. Fast growers and gifted kids both tend to stay in the cognitive and fine motor cases (either their bodies are growing to fast for them to LOOK like they're progressing, because they're constantly having to relearn relearn relearn... or their mind latches onto x, y, z, and they just DELIGHT in those areas for quite some time). It's so prevalent in gifted kids... there's a r.e.a.l.l.y. common name for it : asynchronistic development. In gifted-land asynchronistic development goes one step further if they latch onto one mental area (like math, music, reading. etc.) which gets them years ahead in one area, and actually quite behind in one one or several others).
These staircases make SENSE when you look at them. Kid's brains never stop working. They're always working on something. It's not always as cut and dried as early talker= late walker but if you look at the skills that they're developing, it's something of an AHA! moment. To use the common talk/walk split though: Okay, so we're doing cognitive and fine motor with talking (tongue and lips are the very definition of fine motor)... then with walking it jumps staircases and goes into large motor realm. I've never met a child who can be on all "staircases" at the same time, but many blend two together. It's also the whole "regression" thing. If a child is focusing on one area... the others tend to atrophy a little bit. But since they've already "done" it, they don't have to go throught the whole process all over again. They just have to sort of remind themselves/ remember how they did it before.
R