Answer: False
Explanation: When a human takes part in an experiment, this human is called a "research participant" or a "human subject".
While is true that you may think in these humans as "variables" of some kind, this is not really the case because there is a whole different system, where you just can't do a change in your human subject as you want, so these people are not real "variables" in the experiment.
Then, the statement is false.