I think that the choice made by a subject in a choice task should be behavioral observation. But I am not sure about reaction time and memory, which is more about ability instead of intention.
It may help considering whether the phenomenon is under some control by the participant. Pupil dilation is a physiological measure, but the speed at which I hit a key (reaction time) is a behavioral measure. Memory is a phenomenon. If you meant recall, recognition, or another memory retrieval task, how could you measure that physiologically? Memory is generally measured through (somewhat controlled) self-report. However, it could also be probed through less controllable, more automatic reactions.