I find many Captcha images very difficult to read. I dread finding a Captcha box. I've heard that from several people so it's not just me. I saw a forum posting requirement with a very simple Captcha-like requirement. Text was to put in the numerical answer to a very simple equation like 2+2= . You got one more chance to answer.
I definitely liked that idea. Is it effective? What about something similar like requiring a certain radio button or checkboxes to be checked?