[K9-Lovers]

There must be a trick to this; I've yet to figure it out . . .

Watch: http://www.dogwork.com/mat7/

[ajbrown]

I think the dog can see the cards with the answers

Annie must be taught to bang her foot until she gets a queue which we do not see in camera frame

[JSR22]

I have seen this done. The dog is responding to a hand signal to tap her foot.
She keeps getting a signal until she gets to the correct number. It is a lot of fun to watch.
Jeanne