The eleventh time, with the bag of treats wisely held out of reach, the bell is rung without a treat. The dog, now in a frenzy, barks frantically. The wife yells to please keep that animal quiet. Fearing she might come back into the living room and see the TV on, the father urges the scientist to give the canine some food to shut it up. It gobbles up the treat without appearing to chew and immediately commences barking again.
More food is dispensed.
The dog has discovered that if it wants a treat, it need only to bark. This is called conditioned response. Pavlov would be proud.