[Suicide Junkie]

To sum all that up, For the purposes of the scoffoverse we'll just say that psychic races are psychic, and the best anyone else can do is to learn to block them. I could try to explain it all with technobabble, but let's just not and pretend I did=-)

Why not say that the Psychic race can only pick up your thoughts... If you aren't and don't think about something, its hardly going to be pickuppable, right?
Like a biological CAT scanner or MRI, watching the activity patterns in your brain. And from experience, knowing what they mean...

In conversation, they would be able to try and steer your thoughts by your reactions to what they say and do, making it seem like their abilities are much more powerful than they really are.