Trixie Clicker Manual De Instrucciones página 22

Later it is also possible without food.
After you have diligently practised the command, you do not
need the Clicker any more - for this exercise. Now you can use
the command alone to trigger the desired behaviour from your
pet – without a 'click' and without food. If later you do click
during this exercise, remember that a treat must follow each
'click'.