Updated: Dec 7, 2020
When reactivity is “unpredictable”, it may be harder to work on the problem in a targeted way. However, I do believe there are always signs, maybe subtle, which allow you to anticipate the reaction. In those instances, an owner’s keen eye and dog reading skills need to be developed as much as the dog needs to be trained.
In my experience, especially when the dog triggers in seemingly unpredictable scenarios, for the purpose of training, treat your dog as good as that worst experience. Throw out statements such as “well, he’s good 90% of the time, but there are those few instances where he goes off and I don’t know why”. For intents and purposes of improving the dog, and to keep interactions safe involving others, the dog is as good as those bad 10%.
This sounds more harsh than it’s meant. It highlights to not leave any interactions up to chance or allow the dog to decide whether it’s going to react or not. It puts you in charge of the situation and it allows you to work on problems proactively. Instead of saying “ I wonder if he will react to this approaching dog”, assume he will react - again, for the purpose of training - and get in your dog’s head proactively to start behavior modification before you get into an unprepared situation and start fire fighting.
I’ve found this to be a helpful approach over and over. It’s to help you get into a prepared state of mind while setting your dog up for improvements.