Q: I received an email inviting to register in two sessions and I wanted to register in both. After I registered in one the other disappeared. Could you please fix this?
A: The reason it disappeared is because the design of the most experiments requires that no one should participate in the same experiment more than once (a so-called "between subjects design"). Therefore, registering into one automatically makes it impossible to register into any other session of the same experiment.
Q: On the list of sessions I have registered for there no an "unregister" button. How can I check out?
A: For the majority of the experiments it is critical that everyone who registered will show-up. Therefore, you are expected to show-up unless there are adverse circumstances beyond your control such as illness. If the latter, unfortunately, happens, please notify the experimenters by email at the earliest possibility.