Throughout history, dogs have been considered humans’ best pets and, in folklore, the best “theological spokespersons.” Why is that? Let’s first take a look at some common folk beliefs about dogs: There’s a saying, “Dogs can see ghosts, while cats can see souls.” In rural areas, older superstitious people often tie a large dog outside their homes, believing it can prevent ghosts and evil spirits from entering. If a dog suddenly starts howling with a cry-like sound, it’s believed to be a sign that disaster is approaching — certainly not a good omen. In tomb-raiding dramas, black dog’s blood and black donkey hooves are often portrayed as powerful tools for exorcism. In horror movies, on moonless nights, just before the “ghosts” appear, it’s always the dog and its chilling howl that set the eerie tone.Now, if we consider these beliefs as mere superstitions, what do we make of the fact that dogs sometimes suddenly freeze, barking at thin air when no one is around? At times, they even bark while backing away, looking visibly frightened. What does this mean? After reading this, you might be feeling a chill down your spine—could it be that dogs really are seeing something they shouldn’t? Rather than delving into the mysterious and paranormal, let’s approach this from a scientific perspective: What might dogs be sensing or seeing in the air around them?
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Dog Vision
Many people assume that dogs have better vision than humans, but in reality, dogs are true nearsighted creatures. If the object is stationary, they can see up to 50 meters at most. Compared to humans, the visual effect a person sees from 22 meters away is the same as what a dog sees from 6 meters away. However, some dogs, like Labradors, have relatively good vision. Dogs’ night vision and dynamic vision are much stronger than humans’, and their field of view is also wider. Vision primarily relies on the retina, which contains two types of light-sensitive cells: rods and cones. Cones detect color and detail, while rods are responsible for detecting motion and vision in low light. It’s clear that dogs have more rods than cones, which gives them excellent night vision and superior motion detection. Tests show that dogs have only one-tenth of the cone cells that humans have, so their ability to perceive color is weak. In a way, dogs are colorblind, similar to humans with red-green color blindness; they can’t perceive certain colors. Humans are sensitive to red, green, and blue, but dogs only respond to blue, purple, and yellow, with other colors appearing gray. The world dogs see is like a distorted color TV.Despite being colorblind, how do guide dogs help blind people cross streets at traffic lights? Though dogs can’t see the traffic lights, they are incredibly smart. After training, they can use surrounding noise and the movement of people to determine when it’s safe to cross the road.
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Dog’s Sense of Smell
We often use the term “dog’s nose” to describe someone with an excellent sense of smell, which shows how powerful a dog’s sense of smell really is. It’s thanks to this talent that one dog was hunted down by the largest criminal gang in Colombia. This dog, named Sombra, is a 6-year-old German Shepherd who grew up in the anti-drug unit. After extensive training, he became an excellent sniffer dog. With his help, the police successfully carried out at least 245 arrests and intercepted over 2,000 kilograms of drugs at the busiest port, often hidden in fruit, suitcases, and the nooks of ships. No matter how well-hidden the drugs were, Sombra’s incredible sense of smell helped find them. In one case, he found 10 tons of contraband, causing the gang significant losses. In retaliation, the largest Colombian crime syndicate offered a reward of 200 million Colombian pesos (about 70,000 USD or 400,000 RMB) for Sombra’s head in 2018. To protect Sombra, they had to move him to a new home, with armed guards escorting him every day.Dogs are natural scent experts, with up to 300 million olfactory receptors in their noses, compared to just 6 million in humans. The part of a dog’s brain that processes smells is about 40 times larger than ours. Dogs’ sense of smell is so powerful that they can detect a single drop of special liquid in 20 regular swimming pools. For centuries, humans have relied on dogs’ keen sense of smell for hunting, searching, and detecting drugs, explosives, and even diseases like skin cancer, lung cancer, breast cancer, and bladder cancer.
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Dog’s Hearing
A dog’s hearing depends on the breed and age, but the average hearing range is typically 67Hz to 45,000Hz, while a normal human’s hearing range is 20Hz to 20,000Hz. Due to poor lifestyle habits, most adults can only hear up to 16,000Hz. This means that dogs can hear sounds that humans can’t. What does this mean for dogs? The dog whistle used in training can only be heard by dogs, not by humans. A sound that may seem loud to us may scare a dog. Even on a quiet night when humans are sound asleep, the dog’s world is noisy, preventing them from getting any rest. Dogs can hear the high-frequency pulses from a digital clock’s crystal resonator and even the vibrations of termites inside the walls.
In summary, although dogs are nearsighted and colorblind, they are naturally equipped with night vision, capable of hearing sounds that we cannot, and can detect smells from far distances. If you believe in “ghosts” or supernatural beings, then dogs might indeed have the ability to sense these entities. However, if you’re more of a scientific thinker, a dog’s sudden barking simply means it has heard a sound that caught its attention or smelled something unusual (perhaps your neighbor is grilling chicken legs again). Or, it could be that as night falls, the dog notices a stranger sneaking through the door. All of these are beyond human perception.
