Can Dogs Tell Identical Twins Apart?

Have you ever had a set of friends who also happened to be identical twins? If so, how many times have you struggled to tell them apart? Looking for small discrepancies in their appearance, we're sure you've found yourself questioning your own judgment when it comes to which twin is which. 

Interestingly enough, dogs don't seem to have this difficulty with discriminating between identical twins at all. Recent scientific research is beginning to shine a light on how exactly it is that dogs seem to be better at telling apart identical twins than both scientific tests and humans are!

If you yourself are an identical twin who has owned a family dog, you probably have no question about whether your dog can tell the difference between you and your like counterpart. After reviewing the literature, there are countless tales of identical twins having different relationships with the same pooch. Whether it be the dog is more favorable towards one twin compared to the other, or they respond differently to the twins, it’s clear dogs can tell twins apart. 

What are some signs your dog is able to recognize one twin from another? Well, the signs would depend on the situation. If you're in a situation where you own a dog, and you're an identical twin, it's likely you will get visits from your sibling during your dog’s lifetime. 

It's during these visits that you would notice your dog would not act the same way towards your twin, as they do you, which you wouldn't expect if they truly couldn't tell you apart. You may notice your dog becoming more interested in the unknown twin, showing signs of alertness and curiosity. Sniffing the twin is a telltale sign that your dog is differentiating between the two of you, as you will learn more about in the science section. Your dog may also look back and forth between the twin persons, trying to understand the situation

The history of our understanding of dogs being able to distinguish between identical twins goes back over 50 years. Interest in identical twins has existed for centuries, and more recently, a canine's abilities to distinguish between twins has become of interest.

Why, you might ask? Well, if you didn't know, identical twins are not only identical in their physical features. In fact, they also share such similar DNA, that most tests can not differentiate between which twin is which. How is this possible? When identical twins are inside of their mother’s womb, they actually begin as one fertilized egg that splits into two different embryos.

As a result, the genetic information inside each half is almost if not identical when the twin is born. Of course, environmental factors and experiences will definitely result in genes expressing themselves differently, and therefore causing alterations in their DNA, but even so, their DNA remains remarkably similar. 

This is different from fraternal twins in that fraternal twins are actually two, separate eggs fertilized that grow together in the womb. As a result, the twins most likely have different physical traits and characteristics, and can even be different genders. This is why fraternal twins, though still part of the research, are not the focus of the studies being done. Identical twins are of interest because they come from the same fertilized egg.

It wasn't until a study conducted in the Czech Republic involving 10 German Shepherd dogs, was it clear that a dog's ability to differentiate between twins lies in the superior olfactory system.

There have been a variety of research studies conducted over the past fifty years that have looked at whether dogs have the ability to tell identical twins apart or not. Interestingly, the studies had mixed results, where different dogs had different accuracy rates at making the differentiation.

Throughout the past decade, more specific studies have come to prove that the discrepancies experienced in the research were actually due to the dogs in question. The level of training that dogs in the experiment had differed. The breed of the dogs also often varied between studies, making it hard to conclude how accurate they actually were at determining the difference between twins.

It wasn't until more recently that a credible study was done involving 10 German Shepherd canines who had received vigorous scent training and practice. The dogs came from three different Czech Republic Police Regional Headquarters. The study explored whether the dogs could successfully identify swabs taken from the bellies of two sets of twins after being exposed to the scent of the specific twin in question. 

In all 12 trials completed by the 10 dogs, each dog successfully identified which sample swab came from which twin. Fascinatingly enough, DNA tests could not even tell the differences between the twins, but dogs could.

Why, you might ask? The answer lies in our pooches' exquisite olfactory system that grants them the power to detect scents that humans are unable to detect, including chemical odors emitted by individuals. These odors vary from person to person. Even in twins, there can be pheromone or chemical differences that the pooch can detect which allows them to discriminate between the individuals.