Stimulus discrimination means being able to tell the difference between various stimuli. You dog will learn that a response – such as dropping – will be reinforced when you give the hand signal or voice command “drop”, but not when you give some other signal. Your dog will have to learn the difference between a hand signal for “drop” and a hand signal for “stand”. Many dogs find this confusing in the teaching stage. This is not necessarily the dog’s fault. Many handlers give unclear hand signals. You will find that your dog is probably following your body language. For example you might be trying to lure your dog from a sit to a drop, but because you move your hand too far away from your dog, she moves into a stand position.
Dogs will also discriminate on the basis of unintentional stimuli. For example, the presence of a food lure can become a discriminative stimulus – in other words, your dog will respond to a signal (such as the word “drop”) if you have food in your hand, but not otherwise. This is not a problem with the use of food rewards as such, but rather a training error in the way the food is used. Instructors should give their students more information about the process of phasing out the lure.
It can be quite tricky to work out exactly what stimulus or cue your dog is responding to. Just because you say the word and your dog does the action does not mean he knows the word. He may be responding to contextual cues, body language cues or signals you are unaware of giving.