Initially, generativity is largely a matter of curiosity and play, unencumbered by social coercion. Development of ideas beyond the initial stage requires a network of communicating individuals who can check and build on each other's ideas.
Quoting Isaac Newton:
I do not know what I may appear to the world; but to myself I seem to have been only like a boy playing on the seashore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me.
Regarding Bell Labs (well-known for being highly generative):
“[John] Pierce, to put it simply, was asking himself: What about Bell Labs’ formula was timeless? In his 1997 list, he thought it boiled down to four things:
A technically competent management all the way to the top. Researchers didn’t have to raise funds. Research on a topic or system could be and was supported for years. Research could be terminated without damning the researcher.”
(from The Idea Factory: Bell Labs and the Great Age of American Innovation)
While technically competent management has a clear relation to technical generativity, the other factors are more about absence of negatives (economic and social coercion) than about presence of positives. This makes sense given that (a) at least some humans are automatically generative (in the sense of being curious, inventive, etc) and (b) economic and social coercion destroy generativity. (b) makes sense given that: economic coercion can't incentivize activities the economic system can't test on short timescales (e.g. marketing of consumer goods), and social coercion works on very short timescales and causes conformity pressures (where conformity is incompatible with generativity).
Thus, a question that is more often useful than "what causes generativity", is "what blocks generativity".
Quoting How to Read a Book (1940), page 284 (chapter 18, "How to Read Philosophy"):
"Children ask magnificent questions. "Why are people?" "What makes the cat tick?" "What's the world's first name?" "Did God have a reason for creating the earth?" Out of the mouths of babes comes, if not wisdom, at least the search for it. Philosophy, according to Aristotle, begins in wonder. It certainly begins in childhood, even if for most of us it stops there, too.
The child is a natural questioner. It is not the number of questions he asks but their character that distinguishes him from the adult. Adults do not lose the curiosity that seems to be a native human trait, but their curiosity deteriorates in quality. They want to know whether something is so, not why. But children's questions are not limited to the sort that can be answered by an encyclopedia.
What happens between the nursery and college to turn the How of questions off, or, rather, to turn it into the duller channels of adult curiosity about matters of fact? A mind not agitated by good questions cannot appreciate the significance of even the best answers. It is easy enough to learn the answers. But to develop actively inquisitive minds, alive with real questions, profound questions-that is another story.
Why should we have to try to develop such minds, when children are born with them? Somewhere along the line, adults must fail somehow to sustain the infant's curiosity at its original depth. School itself, perhaps, dulls the mind-by the dead weight of rote learning, much of which may be necessary. The failure is probably even more the parents' fault. We so often tell a child there is no answer, even when one is available, or demand that he ask no more questions. We thinly conceal our irritation when baffled by the apparently unanswerable query. All this discourages the child. He may get the impression that it is impolite to be too inquisitive. Human inquisitiveness is never killed; but it is soon debased to the sort of questions asked by most college students, who, like the adults they are soon to become, ask only for information.
We have no solution for this problem; we are certainly not so brash as to think we can tell you how to answer the profound and wondrous questions that children put. But we do want you to recognize that one of the most remarkable things about the great philosophical books is that they ask the same sort of profound questions that children ask. The ability to retain the child's view of the world, with at the same time a mature understanding of what it means to retain it, is extremely rare-and a person who has these qualities is likely to be able to contribute something really important to our thinking.
We are not required to think as children in order to understand existence. Children certainly do not, and cannot, understand it-if, indeed, anyone can. But we must be able to see as children see, to wonder as they wonder, to ask as they ask. The complexities of adult life get in the way of the truth. The great philosophers have always been able to clear away the complexities and see simple distinctions-simple once they are stated, vastly difficult before. If we are to follow them we too must be childishly simple in our questions-and maturely wise in our replies.
Which is, again, consistent with the picture that humans start generative, and various social forces (especially coercive ones like school, and adults being annoyed at being asked questions, as in diplomat social norms) dim or extinguish the fire of curiosity.
See also: The order of the soul, Better babblers