In this article

1. The experiment with the digital balaclava
2. Why the outline of your head matters
3. What brain scans add
4. Your voice still helps
5. Getting your dog used to your costume
6. Keeping Halloween night calm
7. Signs your dog is worried, and when to get help

You pull on a werewolf mask, walk into the kitchen and wait for the usual wag. Instead your dog stops dead, backs away and barks at you as if a stranger had let themselves in. You are the same person you were a minute ago. To your dog, you may not look it.

Research on how dogs recognise people helps explain why. In lab tests, most dogs leaned on the outline of a person's head and on their hair^{1, 2}, and only a few managed with the face alone¹. Plenty of costumes change some or all of that. Here is what the experiments found, and how to help your dog see past a costume before the doorbell starts ringing.

The experiment with the digital balaclava

The neatest test comes from the Clever Dog Lab in Vienna. Researchers trained 15 pet dogs to tell two familiar women apart, the dog's owner and a friend of the owner the dog saw regularly, by touching the right one's face with their nose for a treat¹. The women sat or knelt inside a box and pushed their heads through two holes in its front, looking straight ahead with neutral faces¹.

Then the task got harder: life-size photos of the same heads, and then the same photos with a digital balaclava laid over them, hiding the hair and the outline of the head so that only the eyebrows, eyes, nose, cheeks and mouth showed¹.

Photos threw the dogs at first, but most relearned the task¹. The balaclava was another matter. The researchers think it very likely that all but two dogs had been using outer features such as hairstyle, and could not switch to the face itself when that was all they had¹.

The two successes show that dogs can in principle tell people apart by the face alone¹. It was a small study, with women only and the same two faces throughout.

Why the outline of your head matters

A team at the University of Padua then asked a plainer question. Given their owner's head and a stranger's, poking through openings on opposite sides of the room, which would a dog walk up to²? With a clear view, dogs went to their owners more often than chance. With a poorer view (the head at an angle, uneven lighting and the outline hidden), they did not².

A second experiment pulled those changes apart. Seeing the outline of the head was what let dogs find their owner; a face turned to the front, or evenly lit, was not enough on its own². The authors called it the first clear demonstration that dogs recognise human faces, with the outer parts of the face key to it².

Still, the inner face counts, and the eyes may count most. In a small 2014 study at the Vienna lab, seven dogs learned on a touchscreen to pick their owner's photo over a stranger's⁷. Covering the owner's eyes with a picture of sunglasses made the task slower to learn than with the whole face; a clown nose, or a scarf over the mouth, made no difference the study could detect⁷.

Put the studies side by side and the Halloween puzzle makes sense. A mask hides the inner face, including the eyes that seemed to matter most on the touchscreen⁷. A wig, a hood, a witch's hat or a full rubber head changes the outline and the hair that most of these dogs seemed to rely on^{1, 2}. Nobody has tested this on a doorstep on 31 October, so treat it as a reasonable reading of the lab work.

What brain scans add

In people, brain imaging points to dedicated face regions³. Earlier, smaller scanner studies in dogs had found areas that responded more to faces than to objects, but their designs could not separate a response to faces from one to living things or bodies in general³.

So a team working in Budapest and Mexico tried a stricter test, published in 2020. Twenty family dogs and 30 people watched the same short videos of unfamiliar human and dog faces, and of the backs of human and dog heads³. In the people, key face regions responded more to faces than to the backs of heads. In the dogs, no region did. What the dog brains picked out was species: an area on each side responded more to dogs than to people³.

The team say that finding nothing is not conclusive evidence against face areas in dogs, and they point out that dogs are drawn to faces all the same³. Dogs look at us. Their brains just do not seem to organise what they see around faces the way ours do³.

Your voice still helps

If your outline is unreliable on Halloween, your dog has other clues. In a study at Kyoto University, dogs heard a recorded voice, their owner's or a stranger's, and then saw a photo of one of the two on a screen⁴. They looked at the photo for longer when the face and the voice did not match⁴.

The researchers suggest that dogs call up a picture of their owner's face when they hear the owner calling them⁴. That makes your voice worth using when the rest of you looks strange.

The Vienna team suggest that in everyday life, scent and voice may be more distinctive or easier for a dog to judge, and that if sight is involved, movement is a strong candidate¹. One Halloween catch: Battersea notes that some masks muffle or change the sound of your voice, which can confuse a dog⁵.

Getting your dog used to your costume

Battersea's advice on face masks was written for the pandemic⁵, but its steps suit a Halloween mask too. Start at home or somewhere familiar where your dog can relax, and build up over a few sessions if you need to⁵.

Five steps, a few days before

1. Hold it, don't wear itStand beside your dog with the mask in your hand and ask for something they know, such as a sit, until they respond as usual⁵
2. Not ready? Play firstPut the mask on the floor a little way off, play together, then put it away and try again the next day⁵
3. Up to your face, brieflyHold it to your face for a second or two and reward straight away⁵
4. Put it onBuild up over a few sessions until your dog stays calm and responds to you as normal⁵
5. Then someone they live withThey come into the room in their mask without approaching, and you reward your dog for staying calm⁵

If your dog looks worried, go back a step, or cover your face a little at a time⁵. Talk to them throughout in your usual voice, the clue the Kyoto study suggests they tie to your face⁴. We would treat a wig, a hood or a hat the same way.

Keeping Halloween night calm

Dogs Trust notes that dogs may find unexpected knocks at the door and people dressed in costumes unsettling⁶, so most of the advice for the night keeps both away from your dog.

Signs your dog is worried, and when to get help

Barking at a masked figure is hard to miss. The quieter signs of a worried dog are easier to overlook, and the PDSA lists these among them⁸:

If you see these, take the costume off and give your dog some space. If they hide or walk away, let them, and do not follow⁸. If your dog shows signs of anxiety or stress on a regular basis, see your vet first, as there could be an underlying cause, and ask them to recommend an accredited behaviourist or trainer⁸.

Under the werewolf you are still the person who fills the food bowl. Give your dog a few calm sessions to put the two together, and the mask can stay a party trick while they snooze somewhere quiet.

Sources and further reading8 sources

The small numbers in the article link to the source behind each fact. Sources open on their own websites.

1. Discrimination of familiar human faces in dogs (Canis familiaris)Learning and Motivation
2. Recognition of human faces by dogs (Canis familiaris) requires visibility of head contourAnimal Cognition
3. Comparative Brain Imaging Reveals Analogous and Divergent Patterns of Species and Face Sensitivity in Humans and DogsThe Journal of Neuroscience
4. Dogs recall their owner's face upon hearing the owner's voiceAnimal Cognition
5. Getting dogs used to people in face masksBattersea Dogs & Cats Home
6. Halloween adviceDogs Trust
7. Part-Based and Configural Processing of Owner's Face in DogsPLOS ONE
8. How to tell if your dog is happyPDSA