[Socionics] Is activation caused by a deficit or surplus in the Mobilizing Function?

I've seen sources describe the Sixth Function as a sort of fuel or raw material for the First Function, the more the Mobilizng IE is present in the environment the easier is to for the Lead function to perform. Other sources seems to suggest that lack of the mobilizing element in the environment triggers a response in the Lead function springing the person in to action. These two views seem to contradict each other, at least at face value.

So, is it a lack or a surplus in the Mobilizing IE that activates the Base function?