cammom's post also brings up one of the many things that can influence how "gifted" a child seems. When you think of "gifted" as "prodigy" or even just "remembering all the states at 2", "learning times tables at 3", or on being "really fast" - these are all skills that are dependent on gifted to VERY gifted working memory and/or processing speed, as well as interest in the sorts of things that draw that sort of attention.

Children who are truly gifted at reasoning, but not necessarily gifted in terms of WMI, PSI, and/or are not academically/fact collection inclined as small children are less likely to appear overtly gifted. It's a lot easier to underestimate how unusual a child's vocabulary is for a 2 or 3 or 4 yr old, or how unusual their ability to argue their side of a negotiation is, than it is to overlook them delving deeply into science, memorizing countries of the world, playing the violin precociously, etc. What if your gifted reasoner doesn't bother to talk much either, because they are too busy in their own heads?