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.
You may also read a report of the results.
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.