We were working dogs on scent discrimination, and one lady had her sheltie on a table doing two metal articles. Now, there are many ways to do scent discrimination. You can do it by starting with all articles scented and gradually introducing non-scented articles. I do this like any other I would do, establishing the scented article and immediately teaching the dog to discriminate based on scent by introducing an unscented article right away. I'm not sure either approach is better, I'm just more comfortable with this approach.

Anyway, this sheltie had not done scent before this event but she was starting to "get it". She picked the scented article 3 times, and on the 4th time picked the unscented one. The trainer gave no response, and the sheltie dropped the unscented article but it fell right onto the scented one, forming a kind of X. The sheltie started nosing at the articles but couldn't get the unscented one off -- so she picked them both up! And then stood there, proudly, the two articles in her mouth, looking expectantly at her handler. I don't know if the written description gets it across, but it was hilarious and exhilirating at the same time to see this shy little dog working with such determination on a task she had only first learned about 10 minutes before.

This is exactly the kind of moment that makes dog training by operant conditioning so exciting and rewarding.