If I had both the time and the money to commission a similar study, I would design is so the "virtual" option uses virtual reality instead of say, a webcam. Ideally there would be some kind of haptic vest put around each participant so that an analog to physical contact could be approximated (e.g. a hug, a poke, etc). My experience so far building games in VR has surprised me in the sense that small amounts of haptic feedback within the Vive controllers can create a surprising amount of physicality if it is timed well with what the user sees. The brain seems to just fill in the gaps.