28/07/2026
Residual odour... or just odour?
One piece of advice you have probably recieved at some point is, "Don't reward residual odour."
It sounds sensible enough. After all, we ultimately want our dogs to locate the source of the target odour, not where it was this morning.
But the more I've thought about it, the more I've found myself questioning this.
Because, how does my dog know the difference?
Most of us use soaks as part of our training. They're a brilliant tool. They allow us to train safely, consistently and economically. But what exactly is a soak?
In simple terms, it's a material that has absorbed odour from the target and is now releasing it back into the air. In other words, the cotton, felt or whatever we've used has become an odour source in its own right.
Now think about residual odour.
The target has been removed, but a shelf, a drawer or a piece of carpet continues to release that same odour because it’s been absorbed and is now being released.
Sounds pretty similar to me.
One transfer happened deliberately during training. The other happened naturally in the environment.
So if I spend months rewarding my dog for finding target odour that's been transferred onto cotton, what tells my dog that target odour transferred onto wood or plastic suddenly doesn't count?
I'm not convinced we know the answer.
I'm not saying we shouldn't use soaks. Far from it. They're a useful training aid but I do wonder whether, from the dog's perspective, a soak is just another residual odour.
And if that's true, are we asking our dogs to make a distinction that we've never actually taught?
Personally, I choose to reward, or at least acknowledge, residual odour during training.
Not because I necessarily want my dog to stop there forever, but because I want them to be confident that they've detected target odour. Once that confidence is established, I can teach them to work through an odour picture, investigate further and commit to the strongest source when one exists.
To me, that seems clearer than saying, "Residual odour doesn't pay... unless it's on a piece of cloth."
And then, there's another question worth asking.
How often are we presenting completely blank cotton, felt or gauze alongside our soaks? Is it often enough to be certain our dogs aren't learning the material itself?
I always recommend using a variety of soak materials to help the dogs generalise and prevent pairing their odour with a specific material. And they become really good at it, despite differences in concentration, age and the surfaces those odours have contacted. But there is still a lot we don't fully understand about how dogs interpret complex odour pictures.
Perhaps "Don't reward residual odour" is the correct advice.
Or perhaps we've been looking at the problem from our perspective instead of the dog's.
I'm certainly not writing this because I think I have the answer.
I'm writing it because I think it's an interesting question.
And in dog training, asking good questions is often just as important as having good answers.
