I have a lot of experience with this phenomenon. Its definately real, and can get quite epic when you are tripping. One time me and my buddy were dosed up nicely and i went to a girls house, she started feeling "shaky" like she was on acid (like how your hands wobble a little bit) and expressed the contact high. A few other times. Once my buddy came over to smoke me out while i was dosed up nicely again. After smoking me out HE started acting like HE was the one tripping, zoning out and staring at shit, even admitting it(and this guy smokes bud, trips etc). We werent even smoking a sativa strain it was a heavy indica.
I notice this shit happens the most on LSD for me. Its all about the vibes and energy you are putting out. Humans are a socially minded species, we feed off eachother's moods. And when someone is in an epic, mystical mood like one becomes on LSD or silly cybin, that can be picked up strongly by someone who is sensitive to emotions.