There are between five and 21 human senses, depending on who is asked and how they define a sense, but it is generally agreed that five is the minimum. The basic five senses are touch, taste, smell, sight, and hearing. Some people choose to include an additional four senses to the list, which include the sense of temperature, pain, balance, and body position.
Currently, there is no concrete definition of what constitutes a sense, but in general, a sense is a means of perception that is detected by a specific sensory organ; for example, the eye is the organ that allows one to see and the ear allows one to hear. Sometimes senses are perceived concurrently with each other; for example, most people see and hear the person with whom they are speaking.
The Five Basic Senses
It is quite common for people to learn about the world by touching, tasting, smelling, seeing, and hearing things around them; in this way, senses are the means of understanding new concepts and gaining knowledge. In some cases, a person may not be able to use one or more human sense, for example, when a person is blind or deaf. Usually, in such a case, a different sense will be heightened to make up for the lacking one; so if a person cannot see, he may be able to hear extremely well.
Besides the well-known five senses, many researchers also include hunger and thirst; however, this is debatable because there are no specific organs that detect hunger or thirst. Intuition is also sometimes included as a sense, which is also questioned because human thoughts do not take data directly from reality, but rather from a combination of sensory organs to which they are connected.
- Equilibrioception: Simply known as the sense of balance, it is perceived by the position of fluids in the inner ear and can be sent off kilter if one spins around in a circle too many times. Having a sensory faculty for the perception of balance is essential for any bipedal species to stay upright while walking.
- Proprioception: This is the perception of one's body in space or the body's position. Like equilibrioception, the data for this sensory faculty comes from within the body rather than from the environment. Proprioception is what a police officer tests when he or she pulls a driver over to the side of the road for suspicions of drunk driving.
- Thermoception: This sense, also known as the sense of heat, was once thought to be a simple variation on the sense of touch, but it is different as heat can be sensed without actually touching an object. For example, the heat that a fire produces can be sensed without actually touching the flames. Thermoception of external heat sources is quite distinct from the sensation of internal body temperature, which uses a different apparatus.
- Nociception: Nociception is the sensation of pain and was also previously believed to be a variation of touch. As with thermoception, it is not actually associated with the sense of touch for the same reason. Nociception has also sometimes been categorized as three senses rather than one because different receptors perceive pain on the skin, the joints and bones, and the body organs.