This experiment has been completed. No more data will be collected.
The experiment originally ran through December 2010. Discussion of the results . The experiment is being maintained here for the purposes of demonstration. You may still run through it if you wish.
This study has been approved by the Harvard University Institutional Review Board. For questions about your rights or research-reated injury that is not being handled by the researchers, contact Jane Calhounat 617-495-5459.