FOR ANGUS RUPERT, the inspiration came during an impulsive nude skydive. 鈥淎s
I was making that jump I realised that there鈥檚 a lot of information that can be
conveyed through the sense of touch,鈥� he says. As a result, Rupert, a flight
surgeon for NASA and the US Navy, has produced the world鈥檚 first tactile flight
suit. He hopes it will help avoid the myriad accidents caused by pilots becoming
disoriented. It鈥檚 an astonishing innovation. Simply plug your suit into the
cockpit and you can fly a jet fighter blindfold.
The suit is just one of a growing number of applications being developed to
exploit our response to touch. Researchers have shown that the skin鈥檚 hotline to
the brain鈥攚hich is what allows you to swat a biting mosquito without
stopping to think about your aim鈥攃an open up a range of possibilities. As
well as saving pilots and their aircraft, this instinctive reaction to touch
could soon be keeping you from crashing the family car, and guiding you to your
destination. Eventually, the skin may provide a substitute for other, faulty
senses, helping blind people to find their way around and allowing deaf people
to hear.
Tapping the potential of the skin has taken nearly three decades of research.
The first indication that the skin had so much to offer came in 1972 when two
Princeton University psychologists stumbled across the discovery that the sense
of touch could be tricked in the same way that an optical illusion can fool the
eyes. Frank Geldard and Carl Sherrick were trying to figure out how the brain
interprets the sensation of something tapping on your skin. They built an
armband that held three vibrators made from headphone speakers spaced down the
forearm. The vibrators were wired up to a signal generator, which was meant to
give one tap at each vibrator. But the wiring was wrong. Instead of a single tap
at each vibrator Geldard received five quick taps at the wrist, then five more
in the middle of his forearm, then five more on his elbow. But he felt something
completely different. He could feel taps at points between the vibrators, and
reported the sensation of a tiny rabbit hopping up his arm. The illusion became
known as the 鈥渃utaneous rabbit鈥�.
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Geldard and Sherrick spent years exploring this and other aspects of touch.
But they remained largely alone in the field, and progress has been slow.
Worldwide, only about 100 people are researching touch, compared with thousands
looking into sight and hearing. Roger Cholewiak, who now leads Geldard and
Sherrick鈥檚 lab at Princeton, hopes that the tactile flight suit鈥攁nd the
other emerging applications of touch鈥攚ill change that.
For the past five years, Cholewiak has been helping Rupert with the
development and trials of the suit at the Naval Air Station at Pensacola,
Florida. Cholewiak鈥檚 expertise has helped Rupert understand how the
vibrators鈥攁lso known as tactors鈥攕hould be arranged and triggered for
maximum effect.
Initially, they experimented with headphone speakers and pager motors, but
the prototype flight suit now uses pneumatic tactors driven by an air pulse sent
down a thin tube. These give a more powerful vibration than the electrically
driven vibrators, and are less hazardous than plugging a pilot into an
electrical source. They are also much lighter鈥攁 crucial factor in
aviation.
The suit has 32 pneumatic tactors, each about 1.5 centimetres in diameter and
a few millimetres thick. They are arranged all around the torso, with a couple
of centimetres between each tactor. According to Cholewiak, this is about as
close as they can usefully be. 鈥淭he skin doesn鈥檛 work well with high-density
vibrations,鈥� he says.
The tactors are driven by a small motor that pumps the bursts of air
according to the electronic output of the cockpit instruments. In this way, the
pilot can receive tactile information on the aircraft鈥檚 altitude, pitch, roll
and airspeed. But its main job is to tell up from down. 鈥淢ost of the pilots who
died in Desert Storm died because they didn鈥檛 know which way was up,鈥� Cholewiak
says. Thirty per cent of civil air crashes鈥攊ncluding, investigators
believe, the one that killed John F. Kennedy Jnr鈥攈ave been attributed to
spatial disorientation.
Knowing where the ground is involves complex and, most importantly,
continuous inputs from our senses. Normally we use our eyes and our vestibular
system鈥攖he fluid-filled organs of the inner ear that give us our sense of
balance and orientation. But in certain situations, these inputs can be
misleading: pilots can be convinced that they are level when in fact they are
plummeting towards the ground or鈥攅ven more deceptive鈥攖he sea.
Of course there are instruments in modern planes that give information about
orientation. But to read them requires attention, something in short supply when
you lose control in a momentary burst of turbulence, or are flying a plane low
over bumpy terrain while dodging enemy fire. It doesn鈥檛 even have to be a
stressful situation for things to go wrong. Hovering a helicopter, for example,
is an inherently difficult task. Imperceptible movements that go unnoticed by
the eyes, the vestibular system and cockpit instruments can eventually lead to
disaster. When US President Jimmy Carter sent a mission in to rescue American
hostages from Iran in 1980, a hovering helicopter scuppered the
mission鈥攁nd possibly Carter鈥檚 chances of winning a second term鈥攂y
drifting slowly sideways into a troop carrier.
Given a tactile suit to wear, however, even someone with no cockpit
experience can keep a hovering helicopter stock-still. There鈥檚 no need to
interpret the information from cockpit instruments: responding correctly to the
suit鈥檚 pulses and vibrations is entirely natural. 鈥淲e鈥檝e tried to make the
tactile display as intuitive as possible,鈥� Cholewiak says.
So, as the helicopter tilts forward, strong vibrations in the front of the
suit practically force you to pull the stick back. Drifting to one side gives a
vibration on one side of the suit. Roll to the right, and the vibrations move
from your waist towards your armpit. Raise the nose too much, and there are
vibrations at the back of your neck. Your instinctive response to each of these
stimuli is the right one: every automatic response corrects for unintentional
movement.
Spine tingling
The system is so effective at delivering information from the cockpit鈥檚
instruments that it allows military pilots to fly blindfold after just a few
minutes鈥� training. They can even loop the loop and know exactly when they ought
to level out鈥攄uring a backward loop, the tactile suits send a quiver up a
pilot鈥檚 spine, over the shoulders and then down the front to keep them oriented.
The suits can also warn pilots of approaching enemies: a tap in the appropriate
place on the body gives an instinctive understanding of exactly which direction
that enemy plane is approaching from.
Richard Healing, director of the US Navy鈥檚 Office of Safety and
Survivability, is impressed by the suit鈥檚 power. 鈥淢y sense is that it鈥檚 going to
be a very valuable tool,鈥� he says. If all goes well, Healing believes that a
tactile display could become standard equipment in some planes within 5
years.
Other applications of tactile suits are also on their way. Military divers
are trying out their own version of tactile sensors that will enable them to
navigate and communicate in pitch-black seas. And tactile displays are even
making their way into space. Hong Tan, an engineering researcher at Purdue
University in Indiana, leads a research group that has already tested tactile
displays on board NASA鈥檚 鈥渧omit comet鈥�, a plane that flies in an arcing
trajectory to give about thirty seconds of microgravity. Eventually, Tan hopes
to have tactile displays incorporated into the suits worn by NASA astronauts.
This would help deal with the disorientation experienced on space walks.
But Tan鈥檚 other work, which she started at the Massachusetts Institute for
Technology鈥檚 Media Lab, will have more down-to-earth applications. Nissan and
Honda are helping Tan鈥檚 team at Purdue to develop tactile displays for their
cars and trucks. Such displays could be connected to close-range radar systems
to give a punchy warning to drivers when something is too close. If a child runs
out in front of the car, for instance, or you just get too close to the car in
front at high speed, you could get a sharp tap on the chest from a tactor within
your seatbelt. If something is too close to the side of the car, the tap would
be to that side, perhaps from a tactor on one side of the lapbelt. A similar
system could warn truckers reversing blind that they are about to hit something.
Tan鈥檚 research has shown that reaction times can be halved when tactile
information replaces straight visual stimuli鈥攁n improvement that could
save lives.
Tan has also used the cutaneous rabbit to make in-car navigation systems
safer. An array of tactors鈥攎odified Walkman headphone
speakers鈥攎ounted in the seat back can create the illusion of a line moving
across the driver鈥檚 back in any direction, telling them when and which way to
turn. Like the tactile flight suit, this can be used without training: it鈥檚
entirely instinctive. 鈥淵ou don鈥檛 have to think about left or right,鈥� Tan says.
鈥淭he signal is already mapped to the body鈥檚 coordinate system.鈥�
Using the rabbit illusion also means that you need less hardware: there are
nine tactors in the seat back, yet people trying it out report the sensation of
up to four times as many taps as were actually sent. The rabbit builds in
redundancy. If one of the tactors fails, the others can take up its job.
Tan鈥檚 research will even benefit people who don鈥檛 drive. She is linking a
tactile belt to a GPS satellite navigation system, and using the belt鈥檚
vibrations to guide a blind person to their destination. These could replace
navigation systems that rely on beeps or synthesised speech, which can be
dangerous if they divert attention from sounds such as approaching traffic. A
vibration system would also be less conspicuous.
A further goal of tactile research is to help people with hearing problems,
especially those that develop in childhood. Kimbrough Oller of the University of
Maine in Orono believes a young child鈥檚 brain could be trained and reorganised
to receive sound through the skin. 鈥淭he neurological plan is not hard-wired and
fixed early in life,鈥� he says. Charlotte Reed, a speech and hearing researcher
at the Massachusetts Institute of Technology in Cambridge believes that Oller鈥檚
idea might be accomplished using a relatively simple display with only a few
tactors. Varying types and textures of vibrations鈥攕uch as changing
frequencies鈥攎ight allow complex information to be transmitted by simple
equipment. This would keep the cost of tactile hearing down, making it perhaps
tens of thousands of dollars cheaper than cochlear implants.
Touch tones
No one has yet developed such versatile tactors, though, and the limited
market for such devices doesn鈥檛 help speed research along. However, the latest
industry to seize on the potential of touch might make a big impact on tactor
technology. Jan van Erp, an experimental psychologist working at the TNO Human
Factors Research Institute in Soesterberg, the Netherlands, wants to develop
vibrators that will put vibrating 鈥渢unes鈥� on mobile phones. He and his team have
been experimenting to see how easily people recognise the rhythm of a song in
tactile form. Eventually, your phone might be programmed to rattle a tacky
tactile love song when your partner calls, and the sombre touch of the Death
March for calls from the office. Stephen Furner, senior technology manager
at BtexaCT near Ipswich in Suffolk, is excited by van Erp鈥檚 trials. 鈥淚鈥檓 deeply
interested,鈥� he says. 鈥淚 think he鈥檚 come up with a good idea.鈥� Furner predicts
that phones with tactile display options will be available within the next five
years.
Perhaps by that time, we鈥檒l all be wearing smart clothes studded with
built-in vibrators discreetly spread all over the body. So there will actually
be another option for programming the personalised tones of the tactile
telephone. You might decide you want a call from the boss to tap you insistently
and repeatedly on the shoulder, for instance. Or maybe you鈥檒l reserve that
setting for when your other half calls.