Mark Poesch asks on his blog, “Why is it that all children are taught that they have only “five senses”…. Doesn’t a sense of gravity (i.e., acceleration) count as a sixth? …could you live without it?” I responded in the comments that I tend to think that it falls under the sense of “touch” as there’s a physical mechanism in the inner ear–specifically, the macula utriculi and macula sacculi[1]–that is responsible for our sense of gravity or linear acceleration.
No surprise, the Wikipedia entry for “sense” points out that the definition of “sense” isn’t well defined. Given a certain definition of sense, there are nine human senses: vision (sight), audition (hearing), gustation (taste), olfaction (smell), tactition (touch), thermoception (heat, cold), nociception (pain), equilibrioception (balance, gravity), proprioception (body awareness). So, it seems Mark is right, conventional wisdom considers gravity its own separate, dedicated sense.
However, in the comments to his blog entry, I asked: “What about “sense of time”? Is that simply cognition (and not a sense)? Probably.” Of course, Wikipedia has an entry on “sense of time” too, which says: “Although the sense of time is not associated with a specific sensory system, the work of psychologists and neuroscientists indicates that our brains do have a system governing the perception of time.” Why isn’t it associated to a specific sensory system? Is the prerequisite for a sense that it must have a corresponding sense organ? This can’t be, since thermoception, nociception and proprioception fail to meet this criteria. If senses are the perception of stimuli, the passing of time definitely causes a stimulus which we perceive.
It appears that back in 2001, researchers identified that the basal ganglia and the parietal lobe are responsible for perceiving the passage of time. Perhaps this provides for a solid explanation for deja vu and other temporal sensation anomalies?
What do you think? Share your thoughts in the comments below.
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Programmer, husband, father, singer, guitarist, tinkerer, reverse engineer, strange, and living in New Jersey. 
In oliver sachs book “the man that mistook his wife for a hat” there are much of interest to those tracking down and understanding ‘senses’, cognitive sciences grasp on the subject and the social constructs of the senses. Def’ a good read…
we only have a sense of time becuse we spin and it has been drilled into our heads at school since we are babies!!!
To me, a sense is an organ which gives me information about the world outside. Therefore I concider myself to have six senses: Sight, sound, taste, smell, balance and touch.
Touch includes heat, cold and pain. Gravity is a blend of balance, sight and touch (remove one or two of them and You don’t know what You are experiencing). Body awareness belongs to touch (because in a deprivation tank You have no body awareness). There is no “sense” of time, it is a learned perception (You need learned referencepoints to tell the passing of time).
You may have something, and I believe we should look more closely at what ideas about sense actually fall into an already defined category. As you stated, “Touch includes heat, cold and pain.” Some may argue that heat, for example, isn’t the result of touch; it is something we feel. For example, you touch nothing of a roaring fire, but you certainly sense the heat. OR, is it that we “feel” the heat? Maybe it, as well as cold or pain shouldn’t be categorized under touch. They’re just a feeling, because if heat, cold, and pain were actual senses, or even categorized under the touch sense, then why wouldn’t soft, hard, and comfort be as well.
I agree that time is not something we inherently sense and shouldn’t be part of our 5+ senses. If it were, the blind would have no problem sensing time, when in fact, they have a very difficult time sensing it.
The word “sense” has a lot of general usages, e.g., common sense. I would say that what is generally thought of as a sense of time is really the ability to discern duration: short duration sounds, longer duration calls and movements, which obviously involves memory. The general concept *time* seems to me to be a wholly human construct that maps into all sorts of things including the circadian rhythms and the cycle of the seasons.
Here’s a genuine puzzle that I’m researching: many species have the ability to register the numerosity of a cluster of items. In empirical terms it is an animal’s ability to direct its action with respect to whether the approximate amount of items in a cluster, in comparison to some reference amount either in memory or in the present, is more or less than the reference. For example, a small group of monkeys retreats with faced with a larger group; a larger group attacks a smaller group. Many species select clusters of food items based on amount. Pigeons can display this behavior in labs. This is clearly evolutionarily conserved. There is definitely a good explanation for the root of this ability in topographic neural regions of the brain; this kind of region in the auditory cortex enables the relative discernment of lower and higher pitch. In the case of numerosity, this region of the brain is processing perceptual information, and passing it along. A leading neuropsychologist, S. Dehaene, wrote an excellent book about this called “The Number Sense,” with “number” understood as amount and not the language-based marks we call numbers.
The mystery is the topic of this blog: what to call it!
There is also the additional sense, the mind, an internal sense that creates it’s own imaginary stimuli in the form of thoughts. Just as we can perceive sound through our ears, we can perceive mental talk through our mind. Ultimately, the perceiver of all our senses is not an entity, an object that can be perceived but is in fact pure formless, awareness. Interestingly, we can perceive our senses without our physical senses through dreaming. For example, we have no actual physical eyes as the character in our dreams and yet a vivid visual world appears.