Actually, scent detection *is* being trained with operant conditioning and clickers. Steve White was a trainer for one the largest police K-9 units in Washington State, accredited as a Master Trainer in '93 the Washington State Police Canine Association, Steve is also a past Executive Board Member of that body. He's been an instructor for the K9 Academy for Law Enforcement. Steve has instructed at seminars in the U.S., Canada, Mexico, and The United Kingdom. He is currently a primary instructor at Karen Pryor's ClickerExpo. He has taught obedience classes at parks, community centers, and kennels. His articles have appeared in police K-9 and dog training publications in the U.S. and Canada. He specializes in teaching behavior modification, tracking, and scent work through the use of positive reinforcement based operant conditioning. He provides consultation and training to K-9 units on administrative and legal issues, and has been recognized as an expert witness by Washington courts in police K-9 and dog behavior matters.
Do check out the CAAPDT seminar in Calgary, Canada this year. He will be speaking as will Ray Coppinger, so you can get a dose of ideas about pack theory and operant conditioning all at the same time. I hear that if he shows his video on suspect apprehension it will leave you breathless.
Shall I go on?
The Texas Task Force 1 of FEMA uses clicker training. A "clicker" trainer in Keller, TX who procures dogs for DPS (state police), Customs and some private explosive and narcotic detection companies imprints dogs for explosive and narcatic work with great success. Some of the above mentioned use clickers and some don't, but they all use use positive reinforcement to train.