On the checkout page, they are applying the type of behavior design/economics research done by Dan Ariely at MIT ("Predictably Irrational" http://www.ted.com/ta

On the checkout page, they are applying the type of behavior design/economics research done by Dan Ariely at MIT ("Predictably Irrational" http://www.ted.com/talks/dan_ariely_asks_are_we_in_control_of_our_own_decisions.html http://www.ted.com/talks/dan_ariely_asks_are_we_in_control_o...) and the Stanford Persuasive Tech Lab (http://captology.stanford.edu/ http://captology.stanford.edu/).