Activity level
The herding instinct is strong in many Shelties. They love to chase and herd things, including squirrels, ducks, children, and if an owner is not watchful, cars. Shelties love to run in wide-open areas.Shelties usually love to play. They do best with a sensitive, attentive owner. The Sheltie is, above all, a herder and likes to be kept busy, although their activity level usually coincides with their owner's level. Shelties also are very smart, making them highly trainable. Shelties are very good with children. Neglecting a Sheltie's need for exercise and intellectual stimulation can result in undesirable behaviors, including excessive barking, phobias, and nervousness. Fortunately, the reverse is also true: annoying behaviors can be lessened greatly by an hour of exercise that engages the dog with its owner.
Intelligence
Shelties have a high level of intelligence. According to Dr. Stanley Coren, an expert on animal intelligence, the Shetland sheepdog is one of the brightest dogs, ranking 6th out of 132 breeds tested. His research found that an average Sheltie could understand a new command in less than 5 repetitions and would obey a command the first time it was given 95% of the time or better.[5]
http://doggytidbits.blogpost.com
(Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization.)