Hôtel d'échange: Gaslighting

Morton Chang entered the room and observed the unconscious family. He gestured for his assistants to turn over the wife and husband. "I'm beginning a series of experiments on the subject of gaslighting," he said. "We're going to see how this woman reacts," he said, gesturing to the unconscious Janice Hamilton. He had the other three Hamiltons sent down to his lab in the basement. They were carefully photographed, as were their things. He paused, analyzing the data he had on them. What was a good first step?