Hi. My name is Linda and I am a clicker trainer. In the spirit of full disclosure, I admit that I have been using a clicker for many years. My use began with the common gateway secondary reinforcer, the verbal cue (“Yes!”). While that worked well for a while, I eventually found that I needed more. I wanted a marker that was accurate and clear to my dog and something that could provide that immediate “ah ha!” moment in dog training that we all crave.
Recently, my husband suggested that perhaps I am too dependent upon my clicker. It is possible that finding them all over the house, in the pockets of my jackets and jeans, in the car, and oh yeah, one in the refrigerator, had something to do with his concern. I emphatically denied this and insisted that I could quit clicker training any time that I wanted to.
He called my bluff and suggested that I try using food alone, no clicker. Admittedly, I did not react well.
Hyperbole aside, why is it that many trainers, myself included, are so completely sold on clicker training? While the short answer is a forehead thumping “Duh…..because it works so well“, a longer exploration into clicker training, plus a bit of science, is needed to fully understand this phenomenon.
Operant learning: There is a large body of scientific evidence supporting the effectiveness of using consequences to teach new behaviors, a type of associative learning called operant learning or conditioning. Although the consequences that are used can be either aversive or pleasurable, most trainers focus on pleasurable consequences, or positive reinforcers. For dogs, a universal primary positive reinforcer is food, though verbal praise, petting, and play are also important. (Note: A primary reinforce is a stimulus that is inherently rewarding to the animal, with no need for prior conditioning). Animals learn most efficiently when the targeted behavior is immediately followed by delivery of the positive reinforcer. Even brief delays between the behavior and the reinforcer can slow or prevent learning.
The timing issue: Herein lies the problem. In the practical context of animal training, there are numerous situations in which it is impossible for a trainer to deliver a primary reinforcer at the exact time that the desired behavior is being offered. Examples with dogs include when teaching retrieving, targeting distant objects, or moving a paw or other body part in a very precise manner. Secondary reinforcers help to solve this problem. These are signals that are clear to the animal, such as a sound or light flash, and which are purposefully paired with a primary reinforcer. For marine mammal trainers, a whistle is used. For dog trainers, it is the click.
Click-Treat: The sound of the clicker is transformed from a neutral (meaningless) stimulus to a conditioned (secondary) stimulus by repeatedly pairing the click sound with the delivery of a food treat (the primary reinforcer). After multiple repetitions of Click-Treat (hereafter CT), in which the click sound reliably precedes and predicts the treat, the click begins to possess the same properties as the treat itself. Clicker training allows the trainer to precisely target (mark) tiny bits of behavior at the exact moment they are occurring. The click sound becomes analogous to a bridge in time – saying to the dog “That’s it!! That thing that you are doing right this instant is what will earn you the yummy treat that is coming shortly!”
Well, at least that is what we think the click means to our dogs………
The meaning of click: Recently, a team of Australian researchers reviewed clicker training and examined the mechanisms through which clicker training might enhance learning (1). They looked at each of the three functions that dog trainers typically attribute to the click – a secondary reinforcer, a marker of behavior, and as a bridging stimulus. Although we typically give equal weight to all three of these functions, the current evidence, collected primarily in laboratory animals and pigeons, is telling us differently:
Secondary reinforcer? As described earlier, once a clicker is “charged” as a secondary reinforcer, it should possess the same reinforcing properties as the primary reinforcer (treat). This means that the click sound alone, without being followed by a treat, is expected to cause an increase in the targeted behavior and help learned behaviors to be resistant to extinction. An unpairing of the connection between secondary and primary reinforce should also lead to a lessening of these effects. All of these outcomes have been tested in rats and pigeons and the evidence overwhelmingly suggests that a conditioned signal (click), when consistently paired with a primary reinforce (treat) does indeed take on the properties of the primary reinforcer. The researchers also provide evidence (in rats) of a neuropsychological nature – dopamine release has been shown to occur at times that would be expected if a secondary reinforcer was the driving mechanism for learning.
Event marker? Almost all clicker trainers, when asked to explain why clicker training works so well, include some version of “it precisely marks the behavior that I wish to reinforce, at the exact moment that it is happening“. I agree with this account, given my own practical training experiences. But, of course, belief is not the same as evidence. What does the current science say about using an auditory signal to mark behavior? As a marker, the signal (click) must draw the animal’s attention to the event. So, if a signal functions to mark behavior, we would expect to see an effect of the signal, though at a lower intensity, when it is not paired with a primary reinforcer. For dogs, this means that hearing the “click” sound, regardless of its pairing with food, should emphasize that moment and thus enhance learning whatever behavior is occurring. Again, though not tested with dogs (yet), this hypothesis has been tested with laboratory animals. The evidence suggests that learning is somewhat enhanced by a marker alone but that the pairing of the marker with a primary reinforcer is decidedly more potent. While “click” may indeed be a marker for behaviors, this function is intricately related to its role as a secondary reinforce rather than marking an event simply by bringing the animal’s attention to it.
Bridging stimulus? The bridging stimulus hypothesis focuses on the “a treat will be coming to you soon” portion of clicker training and applies when the dog is a distance away or there is a temporal (time) delay between the behavior and delivery of the food treat. According to the bridging hypothesis, rather than simply marking the behavior, the signal communicates to the animal that reinforcement will be delayed (but is still promised). A limited number of published studies have examined this function, but the evidence that is available suggests that an auditory signal (such as a click) may bridge the temporal gap between behavior and food. However, all of the studies used a type of training process called “autoshaping” which is a highly controlled and contrived experimental process. Whether or not a click acts as a bridge in the practical and varied setting of dog training remains to be studied.
Take Away for Dog Folks
The bulk of the current evidence coming from other species, primarily lab animals who are tested in highly controlled conditions, tells us that the major way in which clicker training enhances learning is through the click’s function as a secondary reinforcer. As far as event marking and acting as a bridging stimulus, these may be in effect, but if so, they are in a supporting role rather than being the star players. So what might this information mean for we who love to click?
- In its role as a secondary reinforcer, the click takes on the pleasurable properties of the primary reinforcer, food treats. Pairing of the click with the treat (charging the clicker) is essential to both establish and maintain these properties.
- While clicking without treating will work for a short period of time, repeated uncoupling of the click from the treat will extinguish the connection and the click will stop being effective as it gradually reverts to a neutral stimulus.
- Although most of us refer to the click as “marking” behaviors, the actual marking properties of the click appear to be intricately linked to its function as a secondary reinforcer, rather than having any stand-alone strength in this capacity. Ditto for bridging stimulus.
Bottom line? Given these three suppositions, if you are a trainer and are in the habit of clicking without treating, you may want to stop doing that (2). The power of the click lies principally in its strength as a secondary (conditioned) reinforce, so maintaining that connection appears to be key.
As for me, this evidence provides further support for the strength of clicker training with dogs. Don’t think I will be going through any 12-step program to reduce my dependency anytime soon.
- Feng LC, Howell TJ, Bennett PC. How clicker training works: Comparing reinforcing, marking, and bridging hypotheses. Applied Animal Behaviour Science 2016; Accepted paper, in press.
- Martin S, Friedman SG. Blazing clickers. Paper presented at Animal Behavior Management Alliance Conference, Denver, CO, 2011.
Interested in learning more about canine cognition and training? See Linda Case’s newest book – “Dog Smart: Evidence-base Training with The Science Dog“!