Cairn terriers thrive on attention and training and suffer from lack of it. Without training, he will be bored and destructive, barking to help relieve the tedium. There is very little a Cairn cannot learn if his owner takes the time to teach him. Because Cairns are highly intelligent, training sessions should be fun and challenging. I recommend “DOGGIE BRAIN GAMES”. The games are available in several levels depending on the dog’s abilities. I prefer the plastic rather than wood/pressboard for ease of cleaning and as few as possible loose pieces to lose. There are dozens of companies and even more games. Check web for prices… a few of my favorites