It's kind of splitting hairs with word definitions, but I don't really think the word that best describes what happens is not "guess" but "react". Or maybe a better way of putting it is, if I'm communicating the lead clearly, then you will "guess" correctly every time, or nearly so, so it really isn't guessing at all. You knew what the right answer was. If I give you a flat-out wrong lead (hey, it happens) and you react to it, you didn't guess wrong; you correctly answered the question that was asked. I asked the wrong question. If I give you an ambiguous lead or no lead at all, I should expect to get a random response -- the follow feels like she is having to "guess", and in a sense she is, but in another sense it's impossible to answer a question that was not asked. Either way it's on me.