An aspect of Ane psychology and apparently physiology as well. Ane describe it has having "a little guy in the observers seat noting everything you do".
The Overmind is a function of the Ane three lobed brain. According to modern medical practice. This is also responsible for the Ane Psionic Abilities.
The affect is that Ane are always lucid. If awake you cannot traumatize them sufficiently to make them have memory gaps. Horrible events and personal injury that Humans (mercifully) do not remember Ane can recall in vivid detail. It is a thing that makes the Truthteller discipline possible.
It is also responsible for their rock steady mental state. It is noted that it is extremely difficult to drive an Ane insane. Their center is that strong. Conversely, if you manage to break one mentally death usually follows. They seldom if ever recover.