bots are more persistent than humans. make a captcha sufficiently complex, and the bots will keep trying, while humans will stop trying and go away. redirect

bots are more persistent than humans. make a captcha sufficiently complex, and the bots will keep trying, while humans will stop trying and go away. redirect the flow of humans to a "probablynotabotindex.html" page when they abdicate the captcha, and that good for now. so if you want to seem human, learn how to be impatient, and quit a challange.