A Hidden question

"The Hidden" 1987 is one of my very favorite movies and I think I've got a question I've never seen answered so I wanted your opinions: When we see the bad alien (no name) transfer for the first time from DeVries to Miller, Miller is unconscious and easily maneuvered to opening his mouth. But not seeing any of the other transfers where the victim is awake, I wonder how they are able to be kept still enough with their mouth open? The only answer I've come up with is that the victims become hypnotized to a degree? Not something that I need to be thinking about because I believe in and love the film for what it is... but I am curious. Thanks.