re

If a subject is asked to identify a number of
electrical cutaneous intensity-levels within a
range producing tingling (or vibratory) sen-
sations but not pain, then two levels can be
identified without error. Maxi:aum transmis-
sion of information is possible when using three
intensity-levels Extension of the stimulus
range to include intensity-levels producing mild

ain permits efficient identification of four
Eves, as shown in Fig, 2, The addition of
knowledge of results did not produce a statis-
tically significant gain in information transmit-
ted over that with the extended range alone.
Performance when identifying intensity levels
of alternating current applied to the skin, there-
fore, is about the same as with mechanical
cutaneous vibration: at least three intensities
can be identified efficiently,

Similar results are found. when identifying a
number of stimulus-durations, About’ three

30+

Se

durations of electrical cutaneous stimulation
cari be identified efficiently’, again comparable
to the three stimulus durations used in the
mechanical vibratory communication system of
Geldard’ As was the situation when identify-
ing electrical intensity-levels, the data shown in
Fig. 3 indicate that extension of the physical
range of durations permits efficient identifica-
tion of more than three stimulus-durations.’ An
additional complication, however, is apparent
from the results shown in Fig. 3: e
identification depends at least
the stimulus intensity-level used. Peng ee
dependence of performance efficiency on stim-
ulus intensity is particularly important if the
subject is inexperienced in the task, A similar
sonideration,t the interaction (or confusion) of
intensity of stimulation,

Cinded the toe of costae cents Pre
in the mechanical vibratory system described

t
av

Hvbet the Ese

Extended Range included
Hawkee aod Warn), With the Extended Range, Group 1 recelved Koowledge

i -3-


disaster without necessary dependence upon
normal telephone, radio, or television communi-
cation. The Civil Defense Headquarters could
simultaneously alert all of its key personnel
within the area of responsibility by transmitting
a radio signal to activate devices worn by the
personnel, receipt of a cutaneous signal permit-
ting these personnel rapidly to execute plans of
action. Large numbers of key personnel could
be alerted simultaneously, whether or not they
happened to be watching television or listening
to the radio at any given moment.

Auditory or visual signals must compete with
many other signals of Similar nature, Very lit-
tle information, however, is derived from the
skin, thus offering the possibility of ease of
interpretation of cutaneous warning signals, It
is neither being suggested nor implied that cu-
taneous signaling replace more tradi-
tonal forms of communication. The addition
of another input channel to the auditory
fod view visual shoul increase the probability of

to si in many sit-
uations. Further’ whe where Pp reason the
ov si] the ont are not evailable the skin may
e ity for effective
communication, "Phe Plowing is offered as an
illustration of other situations requiring trans-
mission of limited information where cutaneous
signals could prove to be a valuable supplement
to lights and. sounds,

Information necessary for guiding an aircraft
on an te path for landing is now
furnished light and sound. Addition

channel, the cutaneous,
easy and would increase
the likelihood of efficient communication. Fur-
ther, Howell"; among others, has shown that
tracking performance with only cutaneous sig-

of another senso
should be relative!

nals is possible, thus demonstrating the possi-
bility of receiving such information when other
sensory channels are not available. It is rela-
tively easy to conceive of other uses for cuta-
neous communication systems offering choices
among limited signal ‘possibilities. For ex-
ample, it might be desirable to have several
different Kinds of emergency warning signals
available in a single system. The equipment
and training problems of a cutaneous communi-
cation system destgned for limited information
transmission should be only slightly more dif-
ficult than that necessary

ing or alerting purposes.

CONCLUSIONS

It may be concluded that cutaneous signal-
ing could be useful for any form of communica-
tion, Transmission of complete messages with
such a system, however, will require consider-
able additional investigation even though feasi- ”
bility has been demonstrated by Geldard. The
best immediate applications of cutaneous sig-
naling are in the areas of warning or alerting,
and for drection-giving among sets of limited
possibilities as in guidance systems. Cutaneous
communications will not replace the eye or the
ear, but in many situations, “tickle talk” can
be useful.

cutaneous warn-

.


“oe

mo

INTENSITY

CURATION

Froune 1. Mechanical Vibratory Cuteneous Code described by Gelderd.? The

sg 2
Ea &
the
KD
v 1
CoO Co

829925
3

i

to each of 5 Vibrators, with 3 Intensity-Levels and 3

‘Durations
permission of the author).

one avoided the use of mechanical vibrators,
which are bulky and require considerable
, and instead used electrical current as
source ‘of stimulation. It has been sug-
gested by the writer’ and by Gilmer‘ that either
dire or alternating’ current would be suitable:
niounted on the body surfage, and have

less bulk and a lower power requirement than
mechanieal Vibrators, Sensity for mechan-
vibration is tu tempera-
ture, whereas the Amount of electrical creat
required to reach absolute threshold apparently
is independent of surface temperature.’ ‘Fur-
ther, ical vibratory sensitivity falls off
rapidlf as locus is changed from bony to fatty
areas of the bodys sensitivity for electrical
current is dependent mostly upon the nerve
supply rather than the thickness of the

Stimulus-Combinations (date from Howell'’,

g

The communication system described by
Geldard utilized several intensities, durations,
and loci, based on studies of the number of
variatiqns along these dimensions which people
could readily identify. Electrical current ap-
plied to the skin may elicit sensations of pres-
sure, pain, warmth or cold, under suitable
conditions, Alternating current at weak in-
tensity levels, however, usually produces a
“tingling” ‘sensation which typically is indis-
tinguishable from mechanical cutaneous vibra-
tion." An increase in the amount of current
will elicit mild pain analogous to that felt
when a needle just penetrates the skin; mild
pain of this nature is tolerated by human sub-
jects without emotional or other disturbances."
The ability to tolerate mild pain with equa-
nimity may be very useful for communication

purposes.


THEORETICAL
MAXIMUM

s &S 8 8

BITS OF It FORMATION TRANSINTTED

3s

oe

%s zy

6 7

NO. OF STIMULUS DURATIONS

Fron 3. Information Transmitted via Absolute Identification of Electrical

vius-Duration with stimuli
caved; Group & wo1 Natve (data from

by Geldard.’. Much additional work remains to
be done on selection of the most efficient stim-
ulus parameters for cutaneous communication,
on the problems of training with an clectrical
Cutaneous system, on is elec-
trical to mechanical vibratory cutaneous comm.
munications. fic

Cutaneous sighalin; lency in vigilance
tasks has’ been compared to performance with
auditory stimuli, Jn situations where subjects

mnded to the presence of infrequently pre-

sented, electrical Sols ot meghmnteal vil
, Or auditory: si; ofa intensity-
jer, response ‘latency and al detection
were stimuli." “
Efficiency of cutaneous signal detection rel-
ative t. that with auditory stimuli was well-
maintained, however, in another study where a
moderate (rather than weak) stimulus intensity
level was used." In the latter study, efficien
of résponding to the presence of the signals
remain high even when the intersignal interval
was as long as 600 seconds.

Nevertheless, performance deteriorates with
time-on-task for moderate intensity cutaneus

Cutaneous Stim-
at 2 Intensity-Levels. Group 1 was Experi.

Hawkes’).

stimuli if the subjects are req::iied to discrimin-
ate among stimuli as opposed to responding
to its mere presence. When cutaneous or audi-
tory stimuli are presented under alerted condi-
tions, jud; ts of stimulus-duration for these
two Kinds of stimuli are not significantly
different. Subjects have no difficulty in dis-
tinguishing between 0.5 and 1.0 second dura-
Hons-with either kind of stimulation. qnowevers
e subject is to to infre-
went ry sstond staal but me to
Cevery 2.0 seconds) presented stimuli of 0.5
second. duration, then deteriorates
with time-on-task for cutaneous signals but not
for auditory ones." If the cutaneous and audi-
tory are intermixed in the same session
(but not presented simultaneously), then detec-
tion bility deteriorates for cutaneous but
not for auditory signals, When thé two kinds
of signals are presented simultaneously, detec-
tion probability is about the same as that for
auditory si alone,
Cutaneous vs. auditory signaling at present
may be evaluated on these eriteria: (1) train-
ing time required, (2) speed of reception, and

-4-


e
s

PS ait epee amid a ie EE RAE

2 @ataneows: fe
“404, Fe. Koor, Ky., 1900, pp. 114-130.

REFERENCES

US Army Me

SGeult, R. H., “Hearing Through Sense
‘end Vibration,” J. Frontlin Inst, 204: 1927.
© Geldard, F. A., “Adventures in Tactile Literacy,” Am.
Paychologist, 12: 118-124, 1987.
© Gilmer, B. v. HL, “Possibilities of Cutaneous Electro-
Communication,” In Hawkes, G, R. (Ed.): Sympo-
sium on Cutaneous Senativity US Army Med. Res. Lob.
Rep. No, 424, Ft. Knox, Ky., 1960, pp. 7!

{Grit } Re Gegy Shorthand. New York: Gregg,

weitere of Electial Intensity Level,” i Paychol.,
40: 200-312, 1900. :

+ Hawkes, G. R., “Information Transmitted via Electrical
Garacenes'Sthnatee Duration” J+ Prychol, SI: 259-288

© Hawkes, G. RB, “Absolute Identification of Duration,”
Percept. mot. Skill, 13: 203-200, 1061.

© Hawkes, G. B., “Effect of Skin T. the Abe
* Ba, CET fac bieceicdl Cuvecke” J Appl: Physio
Tz; 10-118, 1988

%® Hawkes, G. B. and Loeb, M., “Vigilance for Cutanous
tad Acdbery Sipuals” J, Avdtory Ree, 1: 272-284, 1961.
1% Hawkas, G. R. and Loeb, My

Si Sigua Sopogth” Ye Pogo, BS: ALLA, 1068
. t

PAA AC 68-9998

4 Hawkes, ©. R. and Wane, J. 8, “Maxtarum 1, for Abe
oe Toot Gutancods Hct Lotehy Level
J. Prychol,, 491, 279-288, 1980,

+ Hawkes, G. R. and Warm, J. 8, “The Sensory Ran;
fae as ieatiatins of tho Skin” Amel Peychal,
73: 485-487, 1960.

bal rien hepa ag on rine |. 8. “Method
Piieary Roost rane °
~ Howell, W. C., “Training on a Vi ‘Communica-
ton Syste.” Unpoblished master’s theals, Univ. Virginie,
© Howell, W. C., “On the Potential of Tactual a
ray of Recent, Findings” Js Hawkes, R
t cutaneous sensitivity.
Med’ Res’ Lab. Rap. No. 424, Pe Kaos, Ky., 1900, pp. I


EI-/-Y

aesipemigheeae, HORE a

TACTILE
COMMUNICATION

an fae se enemreneensct ese netOty!

62-1

FEDERAL AVIATION AGENCY
Aviation Medical, Service

ASTIA

poaente
AUG” 9 1962
hows Be —

TISIA A



(3) vigilance performance. On the basis of-
SN S

report’, cutaneous communication ap-
arently compares favorably to Morse Code on
ef) and (2), but reception speed probably is
severely limited when compared to that for
speech. It may be seen from the above that
vigilance for cutaneous stimuli also is consider-
ably poorer than performance with auditory
si

It seems worthwhile at this point to consider
a matter of relevance to cutaneous systems and
also to all other forms of communication: what
meaning should e assigned to the stimuli em-
ed? In Morse le, two signal durations
Totus auses) are used to form groupings which
stand for letters of the alphabet. “te is gener-
ally recognized, however, that Morse Code is
grossly inefficient when compared to the rate
of information reception from speech (up to
about 250 words per minute) or from re:
(500 or more WPM). Quite a large number
of symbols would have to be available if each
symbol were to refer to different word.
Coded symbol sets, such as used in the Gre
shorthand system, could atly reduce the
number of signals required for rapid communi-
cation; at least some 31 to 50 signals would still
have to be available.’ Alluisi' has offered yet
another suggestion: signals could be used to

stand for the sounds or “phonemes” of

Japanese school are now trained with a
system (termed ) of 51 characters, each
representing a , so that there is
direct g between what is read

and what is heard, Perhaps it'is possible with-
out too much training to have, for , the
three “dots” si; of Morse OF a
locus-intensity-duration combination in Geld,
ard’s cutaneous communication stand
for a speech sound/‘or shorthand symbol rather
than a letter of the bet. $0, Message

rate on co tion systems
might be greatly accelerated.

Although a number of uses for cutaneous
communications may be envisioned, such as in
high-noise areas or for the blind and deaf-
blind, it may be seen from the above that much
additignal work is necessary before a cutaneous
communication system such as that described
by Geldard is readily available for use, Never-
theless, there is a Va:t array of situations in
which cutaneous signaling can be utilized im-

mediately. Possible immediate uses of stimuli
applied to the skin are for (1) emergency wam-
ing or alerting purposes, and (2) providin;
limited information such as is needed for guide
ance or direction-giving purposes,

DISCUSSION

Cutaneous stimuli could be used to give any
Kind of warning or alerting signal. The follow-
ing examples were chosen in an attempt to
illustrate the sorts'of advantages possible with
use of signals applied to the skin rather than,
or in addition to, the eyes or the earz. In air-
craft operation, pilots or other control
nel are now wamed in e situations by
an intermittent light or loud sound. These sig-
nals often are ineffective because the visual
and auditory input channels are receiving a
continuous stream of information from instro-
ments and earphones, a condition termed “chan-
nel overload”.

enough to evoke some pain; it was mentioned
earlier that subjects tolerate mild cutaneous
pain without emotional or other disturbances.”

Another possible tion of cutaneous sig-
naling <x in the earlier mentioned high-noise
area. Near jet aircraft and in many industrial
areas of operation, noise levels are such

Additional ways in which cutaneous signaling
can offer’ advantages may be illustrated in an
example in the area of Civil Defense, The
principles, however, apply equally well to many
situations, Personnel responsible for alerting
and controlling le within a particular area
need. to be informed with minimal delay of the
imminence of enemy attack or other impending

-~5S-


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TACTILE COMMUNICATION

GLENN RB. HAWKES, Pz. D.
Sensory
Paychology Branch


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