On my surveys on MT I ask things like "Why did you choose this answer?". I also made a little script library to record the times they enter answers in fields. I

On my surveys on MT I ask things like "Why did you choose this answer?". I also made a little script library to record the times they enter answers in fields. I throw out any that appear to be scripted or were so rapidly answered as to not have been a real answer. At the price per HIT I paid (0.08 to 0.15), I only had to throw out 2-3 answers out of ~2000 due to someone trying to reply randomly.