Crowdsourcing Social Problems

Recognize the distorted text to your left? That’s a knock-off of CAPTCHA, the ingenious online system for verifying that you are a human user of a website and not some crawling bot. (The punny acronym is short for “Completely Automated Public Turing test to tell Computers and Humans Apart.”) Developed more than a dozen years ago at Carnegie Mellon University, CAPTCHA has been a reliable firewall between sensitive databases and virus-like programs designed to pry into them.