Steve Silberman provides an in-depth interview of Lee Billings, in the middle of writing a book about the discovery of extrasolar planets: "Five Billion Years of Solitude: Lee Billings on the Science of Reaching the Stars".
I do think humans are motivated to daydream about extraterrestrial intelligence, and, to put a finer point on it, extraterrestrial people. They are motivated to dream about beings very much like them, things tantalizingly exotic but not so alien as to be totally incomprehensible and discomforting. Maybe those imagined beings have more appendages or sense organs, different body plans and surface coverings, but they typically possess qualities we recognize within ourselves: They are sentient, they have language, they use tools, they are curious explorers, they are biological, they are mortal just like humans. Perhaps thats a collective failure of imagination, because its certainly not very easy to envision intelligent aliens that are entirely divergent from our own anthropocentric preconceptions. Or perhaps its more diagnostic of the human need for context, affirmation, and familiarity. Why are people fascinated by their distorted reflections in funhouse mirrors? Maybe its because when they recognize their warped image, at a subconscious level that recognition reinforces their actual true appearance and identity.