Dont beleive that video either..
You can however tell early on in veg if you veg them in front of a flatscreen TV. Heres how..
If you want to find a female plant, put QVC channel on and the female plants will grow towards the screen quite quickly.. the males will wither away like they are getting robbed..sometimes in a matter of hours.
If you are looking for male plants for breeding (as they are useless at everything else,) then put sky sports on and the males will start singing, waving their branches about and demanding cans of lager and pizzas.
Do not put the plants in front of the graham norton show, or a dame edna everage dvd.