I am not saying anyone would consciously set out to deceive (as you say that would be pointless) but I found that reading the questions I became aware that I was considering what was my actual response and what I thought the 'right' answer was (whatever 'right' means in this case). It was at a purely subsconscious level but I became aware that I was 'playing a game' with myself after the first few questions and after that tried to answer the questions from the gut rather than thinking about the answers. This probably says a lot about the way my mind works in itself !!!

Te trouble is that all multiple choice questionnaires tend to have this effect on me and I wondered if other people had similar difficulties in answering them in a detached manner.

I would guess 'pretend games' would push you away from the autism scale because a characteristic of autism is the inability to see the world from another person's point of view - a pre-requisite for pretending.