Our senses enable our brains to make sense of our surroundings. In school, many of us learned that humans possess five primary senses: sight, hearing, smell, taste, and touch. We were also informed that various animals experience these senses, although often within differing parameters. For instance, humans can perceive red, green, and blue light, while many bird species can see these colors as well as ultraviolet light; on the other hand, dogs are limited to seeing shades of yellow and blue. Additionally, humans can hear sound frequencies up to around 23,000 Hz, but dogs can detect sounds reaching up to 45,000 Hz. Yet, these are not the only five senses recognized. Although the total number varies based on definitions, many researchers argue that humans possess at least nine senses, and some suggest there could be several dozen! Moreover, numerous other animals have extra senses that humans do not. Below are some examples of these senses.
Body Awareness
Proprioception refers to sensing the position of your body, while kinesthesia relates to the awareness of how it moves. These senses are crucial for maintaining balance and applying the right amount of force necessary to carry out daily activities. The ability to walk with your eyes shut stems from the fact that proprioception and kinesthesia operate independently of sight. They depend instead on sensory receptors located in your muscles known as spindles. Each muscle spindle wraps around muscle fibers. When a muscle is extended, these spindles convey information about the stretch’s length and speed to your spinal cord and brain, which then determine your body’s positioning.
Pain
The experience of acute physical discomfort is termed nociception. When tissue sustains damage during an injury, pain receptors known as nociceptors activate and send an electrical impulse along a nerve to your spinal cord. The nerve fibers responsible for conveying pain signals differ from those used to share information regarding proprioception and touch. Upon receipt of the signal, your spinal cord may elicit a reflex action, like flinching away from the painful source. Simultaneously, your spinal cord transmits signals to your brain, which interprets the signals, allowing you to perceive pain. This process equips you to steer clear of the pain source in the future.
Temperature
Humans possess various kinds of thermoreceptors that can identify warmth, cold, or both. Temperature sensations travel along the same nerve fibers as pain signals, which explains why extreme temperatures can be perceived as painful.
Balance
Our balance is governed by the vestibular system found in the inner ear. This system includes three semicircular canals that are filled with fluid and contain hairs that detect the movement of this fluid. Each canal plays a distinct role in sensing balance in various directions.
Echolocation
Humans possess depth perception due to having two eyes that offer different perspectives of the world. This provides the brain with sufficient information to assess distances. However, many animals, especially those active at night or burrowing, cannot rely solely on vision to navigate obstacles. Creatures such as some bats, toothed whales (like dolphins), and small mammals employ echolocation to gauge distance. An animal engages in echolocation by producing a series of clicks and listening for the echoes of these sound waves bouncing off obstacles. Considering sound takes time to travel, animals can determine their distance from an obstacle based on how long the echo takes to return. Bats utilize echolocation to hunt for food and avoid barriers. They emit incredibly high-pitched sounds, typically beyond human hearing capability, and accelerate their clicks as they approach their prey to enhance precision. Toothed whales, such as dolphins, also harness echolocation for similar purposes. These aquatic mammals have a specialized structure called a melon, a fatty deposit atop their heads, which helps clarify the reflected sound waves. Notably, humans can learn