Mail Goggles throw five maths problems up on the screen when a user presses the 'send' button. The problems have to be solved within a limited period of time. Being able to do so would cause the system to presume that the user's mental state is sound enough to send appropriate mails. Even if a person is very good at solving mathematical problems, there is an option to ramp up the difficulty of the questions.
However, the questions remain in the arithmetic realm, and do not drift into interesting algebra or calculus. The default setting enables the system between 10 pm and 4 am on Friday and Saturday.
Internet users can change it in accordance with their preferences, reports CBS News. Mail Goggles can be activated by going into Gmail's settings, and turning on Mail Goggles in the 'Labs' tab.
One can adjust how and when it works in the 'General' tab.