"in a typical collaborative memory experiment, participants first encode a list of words and then some time later attempt to recall those words "

I believe the answer is: by themselves, with others, or by themselves

In the beginning of collaborative experiments, all participants would be made to remember a list of items in a secluded room from other (sometimes without even the presence of the experimenters). After the time given is up, they would gather all participants and asked them to recall the memory to see whether the presence of others could affect their memory retrieval.