It really depends for it could be both.
Right Brained is their flee side of the brain, so they are truely nervous
Left Brained is their dominance/smart side...so if they are "acting nervous" it could be that the last owner took it for him truely being nervous, hence he has been "awarded" for pretending to be afraid to get his way.
To me he seems alot like Sonny in his attitude and the way he was in the video. So to me, without really meeting him and what not, he sounds like a LBE.....meaning he has more go
Even though a horse is more left brained than right, they still have the right brain. It IS possible to get a RB reaction from a LB horse and it isn't necessarily hard. If you truely think he's turning RB when you go to load, ask him to load...but again don't let him pass between you and the trailor, and when he loads up...praise him, then tell him to step out and start it over and over until he'll just jump in.