It does not. 30 college students. There could be a number of reasons why they would fuck up a test like that, for shit and giggles, because it's hip to be awkward, because they didn't really understand what "inner voice" means? its so natural that it's easy to oversee, or they related it to movies where e.g the murderer or whatever is driven by "demonic inner voices" etc - which is something else.
For these kind of studies i think i'd like a video to see how serious or non serious the responses are + i'd like to see how its presented overall. You can prove anything by how you are asking it to the participants.