I once dreamed of traveling around the world with a sword, but I found that I forgot my phone at home... Why are some people "difficult to navigate"?

Produced by: Science Popularization China

Author: Zhang Wenhua (Postgraduate student at the Institute of Geology and Geophysics, Chinese Academy of Sciences)

Producer: China Science Expo

Navigation has become an indispensable part of our lives. Whether using mobile maps or car navigation, we rely on these technologies to help us find the way. Some people even become "directionally challenged" after leaving the navigation. I once dreamed of traveling the world with a sword, but found that I forgot my phone at home... I couldn't move a step!

In sharp contrast, homing pigeons can return accurately even when they are more than 1,000 kilometers away from home. What exactly gives them such excellent navigation capabilities?

How do homing pigeons navigate?

Homing pigeons are birds with remarkable navigational abilities, able to travel to distant places and return accurately. This ability depends primarily on several biological characteristics and environmental factors:

1. Perception of the Earth's magnetic field:

The excellent navigation ability of homing pigeons is closely related to their perception of the Earth's magnetic field.

Many migratory animals, such as turtles, whales, and migratory birds, can travel thousands of kilometers each year. American scholars have found that green turtles are very "sensitive" to the differences in the intensity and direction of the geomagnetic field between different geographical locations, and they can draw a map for themselves through the geomagnetic field.

Research shows that there is also a special raised area between the eyes of homing pigeons that can sense the earth's magnetic field. This area is called a "magnetic receptor," through which pigeons can sense the direction and strength of the earth's magnetic field. Consider a pigeon as a semiconductor with a resistance of 1000 ohms. When it flies, its wings cut through magnetic lines of force, thus generating an induced voltage between its wings. Pigeons fly in different directions, cutting magnetic lines of force in different directions, so the induced voltage generated is different in magnitude, which can be used to distinguish the direction.

The direction sensing organ of homing pigeons

(Image source: Wikipedia)

2. Visual cues:

In addition to sensing the Earth's magnetic field, homing pigeons can also use visual cues to navigate. They can use features of the surrounding environment, such as mountains, rivers, and buildings, as reference points for positioning, which is similar to the principle that people remember routes through special signs on the road. In addition, in clear weather, homing pigeons can also correct their flight direction by observing the position of the sun. Similarly, people can also identify the direction they are traveling in the wild by observing the sun.

3. The role of biological clock:

The biological clock of homing pigeons also plays an important role. The biological clock of pigeons allows them to perceive the passage of time, which is actually like a kind of "clock" in their body. This "clock" enables homing pigeons to adjust their flight path according to the movement of the sun. Whether it is summer or winter, or in different weather conditions, they can rely on this ability to fly back to their nests accurately.

4. Perception of polarized light:

Homing pigeons also have a special ability to "see light" - they can see polarized light, which is invisible to the human eye. When sunlight passes through the atmosphere, it interacts with water molecules and dust particles in the air, causing the direction of the light to change. This changed light is called polarized light. Simply put, polarized light is like light "aligned in a certain direction." The eyes of homing pigeons can identify the direction of these "aligned" light rays and thus determine the position of the sun, even if the sun is blocked.

For example, when a person stands on the beach, even if they cannot see the sea, they can know that the sea is nearby through the wet sand under their feet. Similarly, even if homing pigeons cannot see the sun, they can sense the position of the sun through polarized light and maintain the correct flight direction. This ability is like a "built-in navigation system", which makes it difficult for them to get lost and allows them to return home safely even in bad weather.

How homing pigeons determine direction

(Image source: self-made by the author)

Do all pigeons have the ability to deliver messages?

Although homing pigeons are known for their excellent navigational abilities, not all pigeons have the ability to deliver messages. Homing pigeons are specially bred and trained to have a stronger sense of direction and homing ability. Ordinary wild pigeons and other pigeons may not be able to achieve the same abilities.

The selection and training process of homing pigeons usually includes the following aspects: First, breed selection: The selection of homing pigeon breeds is the key. Excellent homing pigeons usually have strong homing ability, flight endurance and good health. Therefore, during the breeding process, breeders will choose those pigeons with excellent genes for pairing. Second, the training process: In addition to innate individual differences, acquired training is equally important. Training usually starts with a short distance, and then gradually increases the flight distance to adapt the pigeons to different environments and conditions. Reasonable training can enable pigeons to accurately find their way home over extremely long distances.

Why do many people lose their way without navigation?

Compared with the excellent navigation ability of homing pigeons, many people seem very confused and lack a sense of direction without navigation. This is because our brain navigation system is not as good as that of homing pigeons, and this "directionlessness" phenomenon is actually related to the following reasons:

1. The brain has a weak sense of direction;

There is a group of neurons in the human brain that specialize in helping us sense direction, called direction cells. They are responsible for processing spatial direction information, just like a compass that can tell us the directions of east, south, west and north. However, some people's direction cells may not be sensitive enough, so they are easily lost in unfamiliar environments and cannot distinguish between east, west, south and north. Simply put, it is because these people are born with a "dull" sense of direction. For example, when some people are driving, even if they only turn a few times, they can't figure out which direction they are going. This is because their direction cells failed to "calibrate" the route in time.

2. Poor spatial perception;

In addition to the sense of direction, there is a type of neuron in the brain called position cells, which are specifically designed to help us remember our position in space. These cells are like an internal "positioning system" that helps us know where we are, where we come from, and where we are going. However, if the function of the position cells is weak, even if you have walked the same road many times, you may feel that each time is like the first time, with no "familiarity" at all, leading to disorientation. Therefore, such people often get lost in familiar places. For example, after someone goes to the supermarket, they often can't find where they parked their car when they come out, because the position cells fail to help him form a clear spatial map in his mind.

3. Poor visual memory;

Navigation is also related to visual memory, which refers to an individual's ability to remember what they have seen. Many people actually rely on "looking at landmarks" to find their way, such as seeing familiar buildings, road signs, and trees, so that they know they have walked this road before. If a person has a poor visual memory, even if he passes by an obvious landmark, he may not notice it, or he may forget it quickly. Therefore, the next time he walks the same road, everything will feel strange, as if he has never been there before.

Conclusion

With their unique biological characteristics and environmental perception, homing pigeons can accurately navigate in vast spaces and return home. However, humans are affected by factors such as direction cells, position cells, and memory. If the functions of these "brain GPS" are not good enough, getting lost becomes a very common thing.

Understanding these differences not only helps us better understand the navigation mechanism of homing pigeons, but also provides inspiration for improving human sense of direction. By training our own spatial cognition ability, such as reading maps more often, remembering road signs, and trying to find the way without navigation, we may also be able to gradually improve our "navigation skills" in the future and reduce the occurrence of "direction deafness".