It seems to me, and perhaps it will sound pretentious and crude in a way, that intellegence, just as many other things, is a thing that can be spotted in others if one posseses it.
To me, though, intellegence means many things, as opposed to simple knowledge acquisition in certain areas.
If one is musically inclined, for example, from the external perspective of someone not so inclined, with inquiry made to those with that type of intellegence, that it seems to be a given in the right setting. When one is in the space to see musical intellegence, then one does often lead to gravitating towards those with a similar level of intellegence in that field.
Likewise with elite athletes, (ultra)marathon runners for example. Those engrossed in that life seem to have a greater ability to notice those that also posses the requisite ability to excel in that field.
Perhaps it is in the life itself? That those leaning towards excellence in certain areas find it necessary to shed off the bondage of contemporary norms in pursuit of the value they have deemed the utmost importance.
They, no longer, or perhaps ever, have the ability to worry about the ideas of ways to live present in the ‘average’ (for lack of a better term). Once your life has been decidedly driven in a certain direction, and one is secure enough to attempt pursue that direction to its fullest conclusion, perhaps that in itself is the signal that irradiates off of you and makes you reciprically attractive to those striving towards the same ends.
Hypothetically, perhaps the reciprical unconcious feeling of magnetism is ingrained at a certain level? Maybe the cues are linguistically or cultrally embedded. Manner of dress, manner of speech, way of carrying oneself neccessitated in the goal one is trying to reach, ‘ethos’. At a certain level there can only be so many ways cultrally and effically accepted at one given time in a specific culture/subculture.
Could it all be ‘gravitating toward the light’ though?