Lakhani and Wolf uncovered a range of motives, but they found that enjoyment-based intrinsic motivation, namely how creative a person feels when working on the project, is the strongest and most pervasive driver.
Human beings have an inherent tendency to seek out novelty and challenges, to extend and exercise their capacities, to explore, and to learn. But this third drive was more fragile than the other two; it needed the right environment to survive.