Lots of thought goes on in there, just not always useful thought, or coherent thought, or relevant thought. It makes making decisions...interesting. I think I know what my decision will be, but the result is not always as I expect.
My MA dissertation is a case in point. I thought I was set on an idea - transformation in a century of change. Then, as many of the books were Gothic, I shifted to an old favourite of mine - psychological horror. Then, my partner's dissertation - where he is using Russian novels - set me off on the trail of 20th century dystopian novels. There is a theme running through them, none of them are happy-go-lucky love stories, but they're not that closely linked either.
I'm now trotting back to the original idea, but like a skittish pony I am aware of every crisp-packet of a book in the literary hedge. I may just spook and bolt off in a completely random direction. Not for the first time.