Just for funsy!
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How many senses do humans have?
By
Steve Draper,
Department of Psychology,
University of Glasgow. There's a New Scientist article, 29 Jan 2005 by Bruce Durie, on how many senses we have.
The only wrong answer is Aristotle's answer of 5: vision, hearing, touch, taste, smell.
Defensible answers are:
- 3: the number of physical types of stimulus: light (photons), chemicals (smell, taste, and internal sensors), mechanical (touch and hearing).
- 9: vision, hearing, smell, taste, touch, pain, mechanoreception (balance etc.), temperature, interoreceptors (e.g. blood pressure, bladder stretch).
- 21
- 33
Of course the real answer is that this is the wrong way to look at it. Sensing doesn't cause perception: real perception is all about integrating information across senses, across time, across space if you are (as is normal) moving around partly in order to perceive better.
External chemical sensing; Senses of smell; Olfaction
Of the chemical senses of external stimuli, it (currently) appears there may be 4 different sets of sensors:
- Taste.
- The taste buds on the tongue detect 5 different flavours.
- Most perceived taste comes from Olfaction on exhaled air from the oral cavity.
- Olfaction by the Olfactory bulb and nerve, analysing airborne molecules inhaled by the nose.
- Trigeminal: airborne molecules are often also detected by other sensors in the whole nose and oral cavity, transmitted by the trigeminal nerve, perceived as hot/cold, but combined as part of an odour percept.
- Vomeronasal: there is some but insufficient evidence, both behavioural, anatomical, and from brain scans, that humans have a further set of detectors which in animals respond to pheromones, whose sensing we are unconscious of but which do affect us. (We are largely unconscious of some other things, such as a shortage of oxygen in the air, which undoubtedly have huge effects on us.)
The theory of how olfaction works is still undecided, but it seems clear enough that it is like colour perception in that: a) There are a number of different receptor types b) the same stimulus (odour molecule) reacts with several receptor types at once; so that c) it is the ratio (relative strength) of responses that tells a person which odour it, rather than having one receptor type per detectable smell.
Dogs (bloodhounds) vs. humans: sensitivity to odours 10 million to one.
Human sensitivity to a strong odour can be 9 parts per trillion.
A silkworm moth can detect a single molecule of pheromone.
There are some cases of significant differences in what humans smell: like "colour blindness".
Leffingwell,J.C. (2005) "
Olfaction: Update no.5"
Leffingwell Reports vol.2 no.1"
How many senses do humans have?
"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.
Additional Senses
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."
How Many Human Senses are There?
