You can cancel a booking up to 24 hours before your time slot on the experiment is due to run. After this point you are committed to participation and cannot cancel your booking.
To cancel a booking 24 hours or more in advance, go to your research dashboard and click the ‘My Upcoming Experiments’ tab. Click the ‘Cancel Slot Booking’ button next to the slot you wish to cancel, you will be asked to confirm the action. Once confirmed, your booking will be cancelled.