> until you think about it for ten seconds.
It's not about the number of seconds that matter, but it's the direction of where your thoughts go.
I hear this expression often and I don't think it's fair; it's quite condescending. The fact that you think something is obvious and if only somebody bothered really thinking about it for a moment it would be obvious to them too, is missing the reason different people come to different conclusions about things. What you think next is determined by many factors, including your goals, your biases, your prior knowledge, what you had for breakfast.
And you should know that, if you think about it for ten seconds.