They can be trained to some degree. Just like people train goldfish and turtles etc.... They are very small minded and have the patience of an ant, but if you can keep their attention long enough, yep they can learn..... especially things you don't want them too.. hehe.
I teach mine:
the NO command..... very good to have when they are about to chomp an ear
the Wait command - good for keeping them from stealing food out of the feed bucket - lasts only 1 min though....
Down - teaching them to lay down by pressing on their back. Good to getting them to hold still or look less intimidating to the relatives.
Come to a whistle or their name......
Carry Silkies on their backs with a saddle.....