I've never seen a single study that correlates early development with GT-ness. I've seen a lot of claims. I've seen "research" that asks parents of GT kids about development in hindsight, but that kind of evidence is so biased (recall bias) that it's probably useless. If there is any evidence that shows early walking or talking correlates with GT-ness (let alone head control), I'd love to see it. Most of those milestones correlate with when myelination occurs and it makes no sense to me that early myelination in the peripheral nervous system has anything to do with IQ.
This is also something I've often wondered about - in fact, I drafted a post months ago but never got round to posting it. So here it is - it has one study, not exactly about GTness, but it does correlate IQ with early motor development. Don't hold your breath for the size of the effect though....
I've often wondered what was really known about the relationship between a child's very early development and their later giftedness. We have a lot of parents here who mention that their children were early to stand, walk, speak, and are later clearly gifted; we also have a lot who don't fit that pattern. At the same time, people who find their way here are clearly not representative of [any!] population, and so we would not expect their children to be, so just looking at patterns here is not very informative.
[Example, and I hope noone who recognises themselves minds, there have been several even while I've been reading here: a parent of a child under 1yo comes here and says their child is already doing X,Y,Z and they don't know of course but they're here because their child may be gifted. In discussion it emerges that the parent is gifted. At that point clearly yes, it's quite likely that the child is gifted, but that may or may not have anything whatever to do with doing X,Y,Z early, because it has everything to do with having a gifted parent! Somehow, when later it turns out that the parent sticks around and the child is gifted, we've all had reinforced in our minds that early X,Y,Z suggests giftedness, even though that could be a totally bogus association.]
Anyway, so I finally got round to looking for research on this, and here's a reference to one paper I found interesting in case others do to. (The domain I was looking in was peer-reviewed research in reputable journals, involving a large-enough sample of children and not relying on recall of infant development milestones years later after the child's intellectual level is known. These constraints imply, of course, that the research is not likely to relate only to gifted children, and this paper doesn't, but it does include them.)
The paper's interesting, and in a nutshell, it says: yes, there is a statistically robust relationship between early standing, walking, and speaking - but the effect is very small, far too small for the age of milestone achievement of an individual to be useful at all to predict later IQ. They have age-of-milestone against later IQ scatter graphs with best fit lines which are just barely off horizontal: as the abstract says, each month earlier that a child learned to stand corresponded to half an IQ point later. On average, across the population - for an individual, of course, this effect is completely obscured by natural variability.
Now, of course, even this is on only 5000 and some people, so the <em>highly</em> gifted are not that well represented - it's not out of the question that a more striking pattern might show up if you could somehow study just that population. However, for convincing results you really need a prospective study, and of course, for a prospective study to end up with significant numbers of highly gifted children in it, it would have to have a truly huge sample size, so it's not likely to have been done or ever to be done.
Graham K. Murray, MD, Peter B. Jones, MD, PhD, Diana Kuh, PhD, Marcus Richards, PhD
Infant developmental milestones and subsequent cognitive function
Annals of Neurology vol 62 no 2 pp128-136, May 2007
http://dx.doi.org/10.1002/ana.21120Abstract
Objective
Developmental delay is associated with a subsequent diagnosis of learning disability. However, the relationship between the age of reaching infant developmental milestones and later intellectual function within the general population remains unresolved. We hypothesized that earlier attainment of developmental milestones would be associated with better subsequent intellectual performance throughout the range of abilities, rather than confined to extremes.
Methods
Developmental data were obtained at age 2 years in the National Survey of Health and Development, a representative sample of 5,362 children born in the United Kingdom in 1946. Data on intellectual function and educational attainment at ages 8, 26, and 53 years were also obtained. Multiple linear regression and logistic regression were used to analyze the effect of age of reaching developmental milestones on subsequent cognition and educational attainment.
Results
The age of reaching developmental milestones was associated with intellectual performance at ages 8, 26, and 53 years; for every month earlier a child learned to stand, there was, on average, a gain of one half of one intelligence quotient point at age 8. Speech development had a small but statistically significant effect on subsequent educational attainment (later developers were less likely to progress beyond basic education); this effect was not apparent for motor development. Effect sizes were reduced when the slowest developers were excluded, but many effects remained significant.
Interpretation
The association between later development and poorer subsequent intellectual function is small, but it does have theoretical implications; we suggest it is secondary to suboptimal cortical-subcortical connectivity.
