Well, why try so hard to predict what people think, when you can just ask them and they will gladly tell you? As a bonus, you also get a motivation that can be exploited for much better targeting of, uhm, educational ads?
Data gathered from here is explicit, and this much more reliable than what you can implicitly infer from users' behavior.
Data gathered from here is explicit, and this much more reliable than what you can implicitly infer from users' behavior.