Often one of the first questions I get from my students is "do I need to use a clicker?"
The answer is "no!, but you do need a marker signal."
At that point people then start thinking "well, what the heck? I just learned about the clicker, now what on earth is a marker signal?"
The marker signal (also called a bridge or bridge signal) is a stimulus that is classically conditioned to predict a reinforcer.
In other words: it's a signal that tells the horse "yes! That's the answer! A reward is coming"
Now this signal can be anything you like. It can be a word such as "yes!" Or "good!", it can also be a sound like a cluck, a whistle, or a click! It can even be a physical sensation such as a tap on the neck or a hand signal! (This is a potential alternative for blind or deaf horses)
The importance of it is for it to be
1. Consistent—meaning it is the same each time and doesn't have different variations (ex: "yes!" Should always be said in the same way)
2. Distinct—meaning it is different than other cues, and is not used in other contexts (if you use "good!" You shouldn't also use it to tell your horse they are wonderful without reinforcing them)
The clicker is useful because it fulfills both of those requirements and is easy to use. However, many prefer to not have to handle an additional tool, and use a different sound instead. I myself will often use a cluck sound I make with my tongue.
Now while positive reinforcement still works without a marker, having one greatly improves the efficiency of your training. It allows you to mark the exact behaviour you want your horse to learn with great accuracy!
Because the signal is classically conditioned, it actually triggers all the responses in a horses brain that the reinforcer would. So basically the horse feels good the moment you mark, not the moment that the food/reinforcer arrives to them.
So when using a marker, what is being reinforced is whatever the horse did right before the bridge/marker/click.
If you’re not using a marker signal, it’s the reaching into the pockets and pulling out food that predicts the reinforcer and such becomes our marker/bridge.
A great example of why the marker signal is so useful is the teaching of walking forward under saddle
When we use R-/pressure release to train, often time the reinforcer is relief of pressure or "rest" aka. relief from the work or exercise.
Taking walking as our example we would add an aversive or predictor thereof (leg pressure)
And if the horse responds we take the leg of, and/or if they walk until we ask otherwise, they get to stop and rest.
If we are using R+ the reinforcer is often food! Now without a marker signal we tend to just add some food at the end to reward the horse for a job well done.
Since it's quite difficult to feed while walking, what can end up happening is this:
Start walking-walk a few steps-stop-reinforce.
By doing this we are accidentally reinforcing the halting/stopping!
But when we use a bridge signal it allows us to mark the walking. And then we stop to reinforce.
So in this case what we want to do is:
Start walking - walk a few steps - mark - stop - reinforce.
This time the walking was reinforced!
Note that whenever we teach the horse a behaviour, we also want to teach them the opposite behaviour! So if we want to teach a horse to walk forward, we will also have to teach them to stop. And in that case you WILL mark the moment the horse stops. It just all depends on what it is you’re working on in that moment and what is happening in front of you.
Watch to see the difference between reinforcing a stop, vs reinforcing a walk with a marker signal