How to conquer 'little dog syndrome'

Q: I have an 18-month-old Yorkshire Terrier called Butler who barks like mad when anybody comes in the house. When I take him for a walk he tries to bite people's ankles. Can you help?

A: This sounds like a classic case of 'little dog syndrome', where your dog is nervous and uses aggression to keep people away. If the barking has gone on for the first 18 months of Butler's life, then it will be hard to curb, but I would suggest that all visitors call you before knocking on the front door. You can put your little dog away, sit your guests down and ask them to ignore him until he is calm and quiet. Aggression cannot go unchallenged, but don't ever be physically aggressive back, as it will worsen the problem. An assertive and clear 'No' from you will remind Butler that aggressive behaviour on walks will not be tolerated.