© 1975-1979, 2008 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization, First Edition, Xenology Research Institute, Sacramento, CA, 1979; http://www.xenology.info/Xeno.htm

13.1  Tactile Senses

The contact or tactile senses are the most primitive of all. Virtually no terrestrial organism alive today fails to respond in some manner when physically touched. Pressure receptors seem useful in almost any environment imaginable, so it appears reasonable to presume that aliens will have at least some simple tactile sensitivity.

Vibration sensing is a direct extension of the sense of touch. The blow fly is an excellent example. This amazing creature has an elaborate network of vibration sensors along the leading edges of its wings. This serves two purposes. First, the insect is alerted to changes in speed of the prevailing winds. When local gusts greater than about 1 kph are detected, the animal drops down and quits flying against this dangerous headwind. Second, air passing over the wings sets up vibrations of particular kinds. In response to this tactile information, the blowfly carefully adjusts the shape of the airfoil and the frequency of flapping during each wingbeat cycle.⁸² It is a remarkable example of sophisticated biological avionics.

There are many other vibration sensitive creatures on Earth. Earthworms have no eyes or ears, yet they are so responsive to ground vibrations that they can actually feel the footfalls of an approaching shrew.⁷⁹ Among honey bees, ants and other insects touch is both a method of sensing the environment and a means of social communication. Bees are known to be thoroughly distracted by vibrational frequencies between 200-6000 Hz. (One in particular, an octave or two above middle-A, produces virtual anesthesia in the insects.⁸²)

Bees also seem to have an "absolute architectural sense." This enables them to construct perfectly hexagonal honeycomb structures to engineering tolerances of less than 0.1 millimeter. This extreme accuracy is achieved by the use of many tiny tactile hairs located on minute sensory bristles on the creatures’ legs.¹⁰⁰⁰

Could touch be the sense modality of choice for some advanced alien species? It is admittedly difficult to conceive of a plausible environment which would favor touch over all other competing senses. Still, one can imagine dark, turbulent, noisy surroundings which render seeing, smelling and hearing virtually ineffectual. Organisms evolving in such a milieu might be able to glean reliable nonconflictory data only by slowly feeling their way along, sampling the taste, texture, and vibrations in the solid surface below. It would be a kind of two-dimensional existence -- "up," a direction both dangerous and without useful sensation, would have little meaning for these entities.

Such beings, relying almost exclusively on tactile data, could easily develop a most precise and detailed system of communication. Aside from such familiar passive systems as Braille books and typewriters, active techniques might easily be employed even be less intelligent alien lifeforms.

About two decades ago, Dr. W.C. Howell and his colleagues at, the University of Virginia attached a series of vibrators to the chests of male human volunteers. These devices could be triggered at any of three different frequencies, three intensities, and with any of three distinct types of signals (akin to "dot," "dash," and "long dash" in Morse code). A 27-letter "alphabet" was thus set up.

After about 75 hours of training, one student was able to master a language jokingly called "vibratese" by the experimenters. He had become proficient enough to understand sentences vibrated through his skin with better than 90% accuracy, and at a rate of up to 38 five-letter words per minute. (This is better than "proficient Morse" in radio telegraphy.) It was estimated that with further practice, rates approaching 67 words/minute might have been achieved.¹⁶⁹⁴

The significance of "vibratese" to xenobiology is driven home when we realize that many animals on Earth have at least the latent capability for such tactile languages. Consider, for instance, the octopus. These clever cephalopods possess highly responsive sensory tentacles which allow them to chemically sample and feel their way around the ocean floor. In addition to these amazing organs of taste-touch, however, octopuses are also known to be extraordinarily sensitive over all parts of their bodies to tactile stimuli.

This could be an important factor in social communication among these animals, because the octopus can alter the texture of its skin at will. Like a shifting mosaic of brailed skin, the cephalopod’s integument can be altered to display many shades of roughness -- from perfect smoothness, to slightly corrugated, to a kind of "gooseflesh" or tiny raised dots, to larger pimples called "papillae," to even coarser irregularities which have been described as "arborescent projections." A kind of interactive tactile Braille-talk seems quite possible among octopoids, should they ever be of a mind to develop it.

What sort of technology could be mustered by predominantly tactile creatures? Dr. Frank A. Geldard and others at the University of Virginia have extended the earlier work of Howell in a way that gives some insight into the possibilities.

Geldard provided ten subjects with cutaneous vibrators similar to the ones used in Howell’s experiments. The chest devices were buzzed in sequence to give the illusion of direction and speed, and the volunteers were required to turn an automobile steering wheel in response to the perceived motion. The humans proved capable of keeping on target using chest-vibratory tracking just as well as they could using visual clues alone. Writes Geldard:

Although the visual conditions are not optimal for this sense -- the target was "traveling" at the rate of only 3.5 degrees per second, and the eye can handle speeds many times at great -- the tracking task imposed on the subjects was one that would keep all but the speediest vehicles comfortably on course, and the skin was handling the assignment fully as well as the eye.¹⁶⁹⁴

The "Optacon" (OPtical-to-TActile CONverter) developed by NASA is another step in a similar direction. The device converts normal inkprint into a tactile format on an array of small vibrating rods and enables the blind to feel-read without Braille at speeds as high as 90 words per minute. Various attachments allow the unsighted to read typewriter and electronic calculator displays in a similar fashion.

Of course humans are visual, not tactile, beings. The fact that people can do so well is incredible, given that the skin is one of our least sensitive organs. How much more might ETs on other worlds be able to accomplish after their sense of touch has undergone millions of years of evolutionary honing and polishing?

Geldard’s experiments and the results of NASA research seem to suggest that much as radar converts radiation we cannot see into useful visual information on a glowing screen, perhaps tactile aliens, likewise aided by their machines, may be able to drive cars, fly airships, and communicate over long distances using a tactile telegraphy technology.

While a sensorium based mainly on touch seems horribly restrictive to sighted and auditory beings such as ourselves, there may be others in this Galaxy who think otherwise. With eons of natural evolution behind them, such tactile systems could be fantastically complicated, beautifully refined, and far more versatile than any comparable means found on Earth.

Last updated on 6 December 2008