In 2018, I wrote a post titled “My Dog Is Afraid of the Clicker. What Should I Do?” I told the sad story of how I scared a dog with the clicker, then scared her even more by following the standard advice to remedy the situation. In the post, I did something I rarely do, which was to give straight-up advice. I advised people whose dogs were afraid of the clicker to switch to a verbal marker if they really needed a marker, and to leave the click sounds alone for a bit while they determined the extent of the dog’s fears.

I stand by that advice. And now I am going to show you why switching to a quieter mechanical click is not enough of a change to remediate some dogs’ fear.

It’s been great to see more research on training with and without the clicker and the comparison studies rolling in. Many people would be surprised at how many studies of markers, bridges, and secondary reinforcers have been made over the years. I’ve been keeping a spreadsheet of them for quite a while now. For instance, it’s often said that the click sound has special properties in that it is processed by the amygdala. But it turns out that the amygdala is involved in reward expectation and the processing of all predictors and secondary reinforcers—not just the click sound. There is research on this dating back to at least the 1980s.

People have long speculated that the clicker has special effectiveness because the sound is unique. Its short duration and salience seem to help with precision. But do you know what I have never seen? An analysis of that sound compared to other sounds. How long is it, really? What kind of sound is it?

I’m going to show you. Then I’m going to put forth some ideas about the ramifications.

How Can We Communicate about Sounds?

We don’t have enough words in English to describe sounds. As an auditory-oriented person, I run up against this problem a lot. Here is one thing that helps a little. Waveform diagrams allow us to translate the aspects of a sound wave into a visual presentation. So I’m going to give you some examples of what various sounds “look like.” We’ll examine their amplitudes (volumes), rhythms, and onset times graphically over time.

Instead of talking a lot about it, I’m going to show you a lot of examples. You’ll get the hang of it soon enough.

Examples to Get Started

The x-axis (horizontal) is time in seconds. The y-axis is amplitude (volume). I am not including details for the y-axis. These would properly be in decibels. But because these sounds were recorded in different situations, I didn’t control for the distance between the sound source and the mic. Giving readings in decibels would be misleading. I want you to look at the shapes. (If you are curious, the y-axis is on a linear scale to help the user know their recording level. Several of the click sounds “saturated” the scale, meaning that their volume exceeded the bounds of the scale at the distance from the microphone I used. Bad audio engineering behavior on my part!)

I’m not going to get into pitch, because if there are many different frequencies playing at the same time, we don’t hear pitch at all. Most of the sounds I’m going to show you are of this variety. For the piano and violin, the frequency is too high for us to see individual oscillations at the given scale on the page. But most of the sounds are too complex to show oscillations at all.

Here is the C above middle C (C5) on a piano, played at loud, medium, and soft levels. Note how the sound starts off very suddenly (the piano is actually in the percussion family of instruments). Even the very soft one has a definite beginning. Then the amplitude decreases (decays) quickly over time on each one.

Here is the same C played on the violin. String instrument sounds played with a bow don’t necessarily decay. This particular sound starts abruptly, but stringed instruments can also fade in.

Here is what talking looks like. (This is the image of me saying, “Here is what talking looks like.”)

Here is a chainsaw being used to cut down a tree. The last shape is the tree falling.

OK, now we get to the good stuff, the point of this article. I want to show you what the sounds of the clicker and other mechanical markers look like.

Impulse Noises

The following noises are all what acousticians call impulse noises. An impulse noise goes from zero to a high volume in such a short time that it is perceived as instantaneous. Impulse noises are likely more common in human society than in nature. Sudden thunderclaps are impulse noises. Natural explosions can be. But humans create all sorts of impulse noises. Exploding gasses, mechanical impacts, and explosions are impulse noises. Digital noises that are not deliberately faded in, but just “turn on” can be impulse noises. Noise is well studied and regulated by OSHA and the CDC because it can be harmful in several kinds of ways. For instance, very loud impulse noises can cause ear damage because of the suddenness, whereas a gradual noise that peaks at the same volume would not.

You may suspect what I’m working up to. Even though these sounds are quieter, clickers and other mechanical markers have the other characteristics of impulse noises: sudden, with a very fast onset. They are of the mechanical impact type. The suddenness is one aspect of their precision. If you want a short marker, you want it to start (and stop) fast. Here are some examples.

Here is the pop of bubble wrap. Check out the time scale: the loud part is over in less than 1/10 of a second. The loud part is about 0.07 seconds, or 70 milliseconds. I’m going to use milliseconds from here on out. Just remember that 1,000 milliseconds comprise a second.

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Here’s the click of a dog’s plastic buckle collar. Hmmmm, imagine that right next to your ear.

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Here is a box clicker. The two clicks are about 110 milliseconds apart.

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Here is a “bug” clicker. This one was a little harder to do quickly so the two clicks were about 160 milliseconds apart.

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Here is a baby food lid. Note: I learned that they are very unwieldy. Trying to click with a round disc that keeps slipping out of your fingers is not practical! The amplitude is also very different, with the second click much quieter. These clicks are about 100 milliseconds apart.

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Here is a retractable ballpoint pen. I had never noticed that the second sound is louder than the first one, but it is. These clicks are about 170 milliseconds apart. You’ll see in a minute why I’m mentioning the time between the clicks.

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Less Abrupt Sounds

All those clicking sounds started very abruptly. Here are some verbal sounds and a mouth click for comparison.

Here’s the verbal marker “Yip.” It is about 110 milliseconds long. But look how gradually it starts compared to the clicks above.

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Here’s a verbal “Yes.” It also starts gradually and is about 150 milliseconds long.

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Here is a mouth click. It is about 75 milliseconds long.

Onset Comparisons

One of the characteristics of impulse noises is the fast onset of the noise and the quick rise to the maximum amplitude. So for the following images, I zoomed in 10x, that is, we now see the detail in a tenth of a second (100 milliseconds) in the space we were seeing a whole second. This is so we can see the time it takes for the onset of the sound.

Here is the “Yip” zoomed in. It may be only 110 milliseconds long, but almost all of that is the comparatively gentle onset of the Y sound.

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Here is the mouth click zoomed in. Even though the mouth click looks a lot more sudden than the verbals in the images above, check it out when zoomed in. It still doesn’t have the almost instantaneous onset of the mechanical sounds.

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So we can compare the above with a mechanical sound, here is the plastic buckle zoomed in. The amplitude rises to its maximum within just a couple of milliseconds.

Impulse Sounds and the Acoustic Startle Response

I’ve shown graphically how much faster mechanical clicks start than our verbal noises. Here’s why I am focusing on that fast onset.

Mammals have a reflex called the startle response. It can be triggered by a sudden noise, an unexpected touch, or even a purely visual stimulus (think of a silent jump scare on a computer or movie screen). But it is so commonly triggered by noise that that variety has its own term: the acoustic startle response.

In the startle response, the body responds with a rapid extension, then flexion of several muscles. (In humans, these often center on the head, neck, and shoulders, but also extend down to the legs. The eyes blink and the jaw tenses. You probably can summon the kinesthetic memory of your shoulders tensing when you have been startled. If you were sitting down, the quick muscle movement of your legs made you jump out of your seat a little as well.) The criteria for an acoustic stimulus to trigger a startle response have been studied in several species, although not in dogs that I can find. The criteria to acoustically evoke the startle response in rats are 1) that the sound reaches full intensity within 12–15 milliseconds (0.012—0.015 seconds) of its onset, and 2) that the sound is about 80-90 decibels (Ladd et al, 2000). Many texts note that quick onset is essential to the startle response. If a sound is equally loud at its peak but takes more time to rise to that volume, it won’t trigger a startle.

With the onset criteria in mind, take another look at the zoomed-in image of the buckle collar. The time from onset to maximum of that sound is well under 12 milliseconds: it’s less than 5. On the other hand, the onset of the mouth click is more gradual and does not reach as high an amplitude (volume). Again, the amplitudes are not exactly at the same scale, because I did not maintain an exact distance from the microphone over the time I recorded them. But they are roughly representative of the comparative volumes. The mouth click is indeed much quieter than the buckle collar.

Finally, look again at the zoomed in verbal “Yip.” It takes fully 100 milliseconds to reach the peak amplitude.

The Takeaway

• While clickers may not quite reach the criteria to evoke the startle response, they come close. A sensitive animal could be startled by a clicker, especially if the click happens close to its ears. Animals can habituate to startling stimuli, but there is a chance that a sensitive animal will instead become sensitized. And a dog who is sound phobic may respond with fear to a click at any volume.
• If an animal becomes sensitized to the clicker sound, changing to another mechanical sound (jar lid, ballpoint pen) or dampening the original clicker may not work. I’ve tried this with unfortunate results, and I know some of you have, too. I hypothesize that it is because these quieter mechanical sounds still have the sudden onset of an impulse sound.
• From a bioacoustical standpoint, switching to a verbal marker will generally solve both of the problems. It is quieter, and the onset is much slower than that of a mechanical device.
• The total time of a quick verbal marker is comparable to the time between the two clicks of a clicker, so you may not be losing much in precision.

Mechanical clicks, even quiet ones, have the characteristics of impulse sounds, which can trigger the mammalian acoustic startle response. If you’ve scared an animal with a clicker, it’s probably wise to move away from mechanically generated sounds until you know more about their particular sensitivities.

These are my own deductions, based on the acoustic properties of mechanical clicks, the nature of the mammalian startle response, and what I have observed in dogs. I’m not saying that clickers are dangerous for all dogs, or even most dogs. I’m saying that some fearful or sensitive dogs will not habituate to these startling noises, that they may get sensitized instead, and that the sensitization can generalize to other similar sounds, even at lower volumes. There could be errors in my assumptions, and I am open to any discussion on the topic.

References and Further Reading

Götz, T., & Janik, V. M. (2011). Repeated elicitation of the acoustic startle reflex leads to sensitisation in subsequent avoidance behaviour and induces fear conditioning. BMC neuroscience, 12(1), 30.

Ladd, C. O., Plotsky, P. M., & Davis, M. (2000). Startle response. George Fink. Encyclopedia of Stress.(ed), 3.

Rooney, N. J., Clark, C. C., & Casey, R. A. (2016). Minimizing fear and anxiety in working dogs: a review. Journal of Veterinary Behavior, 16, 53-64.

Yeomans, J. S., Li, L., Scott, B. W., & Frankland, P. W. (2002). Tactile, acoustic and vestibular systems sum to elicit the startle reflex. Neuroscience & Biobehavioral Reviews, 26(1), 1-11.

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Copyright 2020 Eileen Anderson