I believe it is common practice to present a participant with a fake high "average value" when performing a task in order to induce stress responses by making them think they're performing poorly. While this relates more to task performance than knowledge, it might be a good direction to look in for references.

I am sure there is a lot of direct and recent research into the subject, but just to give you a couple of classic references, Freud made a very readable (although clearly anecdotal) analysis of the pleasure we derive from understanding a joke in his Jokes and Their Relation to the Unconscious.  After surviving the Holocaust, Victor Frankl developed an entire school of logotherapy that is based on the fundamental tenet of positive therapeutic effects of understanding the sense of one's own life.  Hope this helps (at least, with the first sentence of Introduction ;)

Inglis et al (1997; Free food or earned food? A review and fuzzy model of contrafreeloading.  Animal Behaviour, 53, 1171-1191.  doi:10.1006/anbe.1996.0320) Inglis (2000; The central role of uncertainty reduction in determining behaviour. Behaviour, 137(12), 1567-1599. doi: 10.1163/156853900502727) and Inglis et al. (2001; An information primacy model of exploratory and foraging behaviour.  Animal Behaviour, 62, 543–557.  doi:10.1006/anbe.2001.1780) propose that uncertainty reduction is a fundamental motive.  There is an empirical test of the hypothesis in Bean et al (1999; Contrafreeloading in starlings: Testing the information hypothesis.  Behaviour, 136, 1267-1282.  doi: 10.1163/156853999500712).

This may tie in with work on animal welfare claiming that they benefit from increasing their feeling of control.  I have only seen that mentioned in secondary sources.  You will have to find primary sources yourself.  

You could also search for work on learned helplessness.  If I remember correctly, the crucial control condition is that you yoke two animal together such that both get electric foot shock at unpredictable intervals, but only one of them switches off the shock for both of them.  Both animals experience the same shocks, but one of them has control, the other one doesn't.  The animal without control shows less motivation in other tasks, and learns more slowly.  Learned helplessness is an animal model for depression.

The title on von Stumm et al.'s paper (2011) speaks for itself: The hungry mind: intellectual curiosity is the third pillar of academic performance.  Perspectives on Psychological Science, 6(6), 574–588.  doi: 10.1177/1745691611421204.  It seems plausible to me that the need for cognition that von Stumm et al tested would be selected for by better understanding offering better control over the environment.  If so, then educational psychologists should tell you that it is easier to motivate people to learn something if they know an application than if you abstract it all away from any application.  I only know of anecdotes to that effect, I haven't looked up original research.

If you want to find people strongly driven by the joy of understanding, I suggest you recruit subjects among the pure mathematicians.

All this is aimed at point a).  Your point b) sounds a more like social dominance orientation, rather than curiosity.

Regarding (a), and I'm sorry that this answer is rather vague, I recall reading something along these lines regarding infant development - that small children especially seem to get a kick out of working out how things work. (And also that it makes even more sense that this would be a powerful motivator in early life.) I read the material in question ages ago, though, and so don't recall specific citations. I'd expect quite a bit of inter-individual (and even inter-domain) variation in adults.

As to (a), useful literature may be found using "Aha-erlebnis" or "Eureka effect" as key terms. As to (b), literature on metarepresentational processes, particularly the interpretation of narratives, may be relevant (e.g., studies by Gerrig, Rapp, and perhaps also Gilbert: see references  in attached article). The focus may not be on the experience of pleasure, but it seems plausible that the processes involved may imply Aha experiences.