There's a post on Horsegroomingsupplies about it, apparently it's worked for a lot of people. I imagine it's something to do with the horse focusing on one thing at a time?
Maybe the smell of the glue on it makes them high haha
Seriously though it's amazing, next time the dentist comes for my horse I might try this instead of paying for sedation!
I have been wondering if it is something related to being prey - maybe it makes them act as if it is a snake, which is threatening, hence why some react by going still and quiet (similar to the twitch theory) and others react violently by running backwards away from it.
To be fully convinced I'd need to see both "before" and "after" in order to compare the behaviour accurately.
This YouTube clip failed to show what behaviour the mare was exhibiting prior to the duct tape being applied; so therefore IMO not really possible to establish (a) what the bloke was actually trying to do, and (b) her reaction to it without the duct tape.
Having said that, I just might give it a go for my boy next time I clip his legs........... but am not holding my breath.
Whilst appreciating that sometimes its the quirky things that work, as far as I'm concerned the Jury's still out on this one, for me anyway.