Proceedings of the 2011 IEEE
International Conference on Robotics and Biomimetics
December 7-11, 2011, Phuket, Thailand(c) 2011 IEEE. Personal use of this material permitted. However, permission toreprint/republish this material for advertising or promotional purposes or for creating
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Effects of Presentation of Shear Deformation
to Finger Pad on Tracing Movements
Kenya Matsui, Shogo Okamoto, and Yoji Yamada
Abstract— Human sensory inputs and motor outputs mutually affect each other. This study focuses on the shear
deformation of a finger pad during tracing movements. A tactileinterface influences the sensory–motor relationships during the
tracing movements by manipulating the deformation of thefinger pad. We conducted a preliminary experiment involving
five participants and confirmed that the moving distancesof the finger increased when the finger pad deformations
were amplified by the tactile device. In addition, according
to introspection, the participants perceived variations in thefriction of a sheet of paper on which their fingers slid. We
concluded that the presentation of shear deformation to thefinger pad during tracing affects human motor outputs andthe perceived friction of materials.

I. INTRODUCTION
Human sensory inputs and motor outputs mutually affecteach other [1]. In this study, we pursue the idea that a tactileinterface can influence human motor outputs by intervening
in sensory–motor relationships. For example, Nakamoto et al.
developed a tactile interface to induce a human’s prehension[2] using the relationship between the perception of slippage
on a finger pad and a reflective grasp force control [3].
Watanabe et al. studied a tactile interface for altering walking
cycles by vibrotactile stimulation to feet [5]. Vibrotactile
stimuli to the sole are known to translate the center of gravity
and a its awareness of a person standing still [6]–[8]. For
example, humans feel that their center of gravity moves tothe right by the presentation of stimuli to the right sole.
The abovementioned studies showed that presentations ofeffective stimulation to the human body by tactile interfaces
almost unconsciously affect human motor outputs. As well as
these studies, we investigate how stimulation induces movements rather than whether such inductions are unconscious
or not.
We address tracing tasks as the sensory–motor relationships. A tracing movement is where a human traces characters or figures on a sheet of paper using his or her finger
pad. The tracing movements cause shear deformation of
the finger pad, and such deformations have been analyzed[9]. The objective of this study is to intervene in therelationships between the shear deformation of the finger
pad and the tracing movements by a tactile interface andto investigate how the interface influences the tracing movements and related sensations. Here, related sensations include
This work was in part supported by MEXT KAKENHI 22800030 and
23135514,and Kayamori Foundation of Information Science Advancement.
The authors are with the Department of Mechanical Science and Engineering, the Graduate School of Engineering, Nagoya University, Furocho,
Chikusa-ku, Nagoya, Aichi, 464-8603, Japan

978-1-4577-2137-3/11/$26.00 © 2011 IEEE

skin sensations such as the perception of friction and deep
sensations such as the perception of force. If the presentationof shear deformation to the finger pad influences the tracing
movements, applications such as inducing tracing movementsof a touch-panel interface user by using the tactile interface
can be developed in the future. Clarifying what kind of tactile
stimulus induces what kind of human movement can lead tothe development of novel tactile interfaces.
II. SENSORY–MOTOR RELATIONSHIPSUNDERLYING EXPERIMENT
A. Basic model of sensory–motor relationships during tracing movements
Fig. 1 shows an example of the speculated sensory–motor
relationships between the tracing movements and shear deformation of the finger pad. Humans input a target trajectory
xd on a plane into their own internal models I(xd , µk ) of
the body and environment and decide the finger’s generative
forces F . The internal model is given by as an equation of
motion of a finger sliding on a frictional plane:I(xd , µk ) = F = mẍd + sign(ẋd )µk Fn(1)where m, µk , and Fn are the finger’s mass, kinetic friction
coefficient between the finger and floor, and the finger’s
normal force on the plane, respectively. The generative force
F determines the tracing movements x as a result of theinteraction between the person’s own body and environment.
We describe this operation as x = B(F ). The shear force
fs to the finger pad and shear deformation ds of the finger
pad are determined by this tracing movement x. From theTargetInternal model oftrajectory generative force to fingerxࢊ
F +∆F = I(xࢊ ，௞ + ∆௞ )F +∆FBody &
ActualEnvironment trajectoryxx= ௞ + ∆௞௞ + ∆௞ = E (௦ ∆௦ )Estimation offriction coefficient = -sign()௞ ௡ /௙＋ ௦＋ Shear deformationof finger pad

Presentation of shear deformation ∆௦ = D()to finger padx/ 

m: finger mass, K ୤ : finger pad stiffness

Fig. 1. Relationships between shear deformation of the finger pad andtracing-movement. Black: closed loop without presentation of shear deformation. Red: closed loop with presentation of additional shear deformation(△ds ) by tactile interface.

2479

Finger’smoving direction

Finger’s
moving direction

Tracing
MarkerTracing
Motor Marker Motor

Ch0

Ch0 Finger Ch1

ߤෞ
௞
൅Δ ߤෞ
௞

‫ܨ‬௡

ߤෞ
௞

Motor

ࢌ࢙
Fabricband YΔࢊ ࢙ ࢊ ࢙ࢊ࢙(a) Normal condition(b) During application of
additional shear deformation(a) Side viewFig. 2. Shear deformation to finger pad by tactile interface and perceived
friction coefficientFig. 3.

Amontons–Coulomb law, the shear force is given by
fs = −sign(ẋ)µk Fn .

Z

PulleyZ
X

StringAcrylic
plate(b) Front viewDevice to present shear deformation to finger pad

Motor

(2)

These force and shear deformation are illustrated in Fig. 2a.
The shear deformation is given byds =fssign(ẋ)µk Fn
=−
Kf
Kf

where Kf is the stiffness of the human’s finger pad. This
shear deformation can be used by a person to estimate thefriction coefficient µˆk of the surface [10]. We express theseestimation processes asµˆk = E(ds ).

B. Effect of additional shear deformation to finger pad on
tracing movement
In the experiment, as shown in Fig. 1, we applied theshear deformation ∆ds = D(x) to the participant’s finger
pad using the tactile interface; this is mentioned later. Using
this device, the shear deformation of the finger pad improvesto ds + ∆ds , as shown in Fig. 2b. We speculate that thecoefficient of friction perceived by humans also improves to(5)

The person feeds back this augmented coefficient of friction
to their own internal model and increases the finger force toF + ∆F = I(xd , µˆk + ∆µˆk ).

Fabricband(a) Side viewFig. 4.

(4)

Humans feed back this perceived friction to their own
internal model of the finger’s equation of motion. They thendecide the generative forces to realize the desired trajectories.

µˆk + ∆µˆk = E(ds + ∆ds ).

Antiskid
sheath(3)(6)

As mentioned above, humans perceive the growing friction
by the applied shear deformation to the finger pad, andthen the finger’s generative force improves. Due to suchan underlying mechanism, we speculate that the tracing
movements are influenced by the tactile interface.
The abovementioned mechanism is one possible example.
In this study, this possibility is not necessarily presumed. The
objective of this study is not to identify such mechanisms but
to empirically verify and observe whether the presentationof the shear deformation to the finger pad affects the tracing
movements.

PulleyAcrylic
plate(b) Front view

Photograph of device to present shear deformation to finger pad

III. EXPERIMENTAL SYSTEM
Figs. 3 and 4 show the tactile interface developed topresent the shear deformation to the finger pad. The device
drove an acrylic plate placed beneath the finger pad by
activating two DC motors to which strings were fastened.
The motors (RE-140, MABUCHI) produced a maximum
torque of 7.31 mN·m with an applied voltage of 3.0 V. Two
motors were independently-controlled. The device presented
the shear deformations along the X-axis. The device itself
hardly moved the finger because the sum of internal forces
applied by the device to the finger was zero as a whole.
We confirmed that the drive of the device shifted the finger
by only 0.3 mm when the finger was still. This value isnegligible compared to the spontaneous finger movement
induced by the manipulation of the shear deformation, which
is approximately 7 mm on average (see Sec. IV-B).
A camera (320 × 240 pixels, 30 fps, Playstation eye,Sony Computer Entertainment Inc.) measured the positionof the attached marker on the device. The resolutions of theposition were 0.85 mm and 1.05 mm in experiments 1 and 2,
respectively. We calculated the velocities of the finger using a
Savitzky–Golay filter of filter length 5 [11]. The calculated
velocities were transformed to a device–control computer.
The computer controlled the motor torques of the device witha control cycle of 0.2 ms based on the equations presented
in Secs. IV-A.3 and V-A.3.
IV. EXPERIMENT 1: LINEAR TRACE
We investigate the effects of the presentation of shear
deformation to the finger pad on the tracing movements while2480

the finger linearly traces a 150-mm line drawn on a sheet ofpaper.

Finger’s
moving direction

Z

X

X

A. Method
1) Participant: Participants were five right-handed university students (P1–P5) from our laboratory; we did not include
ourselves in the group. They were told to close their eyes sothey could not see, and aurally blocked by listening to thepink noise through headphones.
2) Task: The participants wore the tactile device on theirright index finger and sat down on a chair in front of thesystem to measure the tracing movements. They traced a line
using the index finger, as shown in Fig. 5. They conducted asingle line trace with the sound of a metronome at 0.75 Hz
and a reciprocating motion for two sounds. They repeatedthis reciprocation three times in a single trial. They practiced
following the metronome for a few minutes before theexperiment until they felt familiar with the task. They were
instructed to trace the 150-mm as accurately as possible.
During the trial, they maintained the finger’s posture so that
it would follow the Y -axis. They visually confirmed theposition of the line at the beginning of each trial and placed
their fingers on the far right of the line, which was designatedas the starting position.
3) Stimuli: We randomly presented three types of shear
deformations to the participant’s finger pad. We did notgive them information about these stimuli. Ten trials were
performed for each stimulus. The three types of shear deformations were as follows:• amplify condition: the finger pad’s shear deformations were amplified along the X-axis(Fig. 6a);• reverse condition: the shear deformations werereversed along the X-axis (Fig. 6b); and• normal condition: the shear deformations were
not presented.

150 mmFig. 5.

Experimental setup

Finger’s
moving direction

Z

Ch0

Ch1

Ch0

Ch1

ܶଵ

ܶ଴
(a) Amplify condition
Fig. 6.

(b) Reverse condition

Shear deformation to finger pad in linear tracing-taska) Amplify condition: When humans trace a line, theirfinger pads commonly undergo shear deformations in the
direction opposite to the finger’s velocity. Under the amplify
condition, the motor’s torque increased to amplify the shear
deformation of the finger pad. Basically, the motors output
torques were Tmax or Tmin . Only when the velocity was
relatively small, the motors’ torques linearly changed in orderto retain the smoothness of the changes in torques. When afinger was moved in the positive direction along the X-axis,
as shown in Fig. 6, and the velocity of the tracing movement
was vx , the tensions exerted on the string of the plate were
 Tmin if 0 ≤ vx < 10α(|vx | − 10) + Tmin if 10 ≤ vx < 150
T0 =
(7)


Tmax if 150 ≤ vx
T1 = Tmin(8)
where α, Tmax , and Tmin were 5.75×10−3 N·s/mm, 1.07 N,
and 0.31 N, respectively. We chose α so that the device
would be likely to effectively influence the tracing movement. Tmax was the maximum tension that this motor could
generate. We set Tmin as maintaining the string tension. T0
reached Tmax at vx = 150 mm/s. When the finger was moved
in the negative direction along the X-axis , the tensions were
given by
T0

=

T1

=

T
(9)
min
T
if
−
10
≤
v
<
0

min
x

α(|vx | − 10) + Tmin if − 150 < vx ≤ −10 (10)Tmax if vx ≤ −150.

We get these equations simply by switching T0 and T1 in (7)and (8). When the velocity of the tracing movement was nearzero, the direction of the force applied to the plate tended
to switch frequently, and the deformation presented to thefinger pad behaved vibrationally. In order to prevent this, we
set an insensitive zone of ±10 mm/s.
b) Reverse condition: This condition transposed T0 andT1 of the amplify condition.
c) Normal condition: Under this condition, the device
did not present shear deformation to the finger pad. The
motor outputs were controlled so that the normal force
exerted to the finger pad along the Z-axis became equal tothose in the amplify and reverse conditions. Tensions were2481

Moving distanceDifferences inmoving distances [mm]

150

0
7

8

9

10

11

12

13

Time [s]Example of moving distancesFig. 9. Average and standard deviation of differences in finger moving
distances for the amplify and reverse conditions with the normal condition
in Exp. 1, ∗∗ significance level of 1%. ∗∗∗ significance level of 0.1%.

Velocity
peak

0

-300
6

7

8

9

10

11

12

13

Time [s]Example of velocity peaks***

Amplify-Normal

Reverse–Normal0-50given byT
if |vx | < 10

 min

1
T0 = T1 = 2 ((α(|vx | − 10) + 2Tmin ) if 10 ≤ |vx | (11)
 1 (Tmax + Tmin ) if 150 ≤ |vx |.
2

Fig. 10. Average and standard deviation of difference in finger’s peakvelocity for the amplify and reverse conditions with the normal condition
in Exp. 1.

Differences inmoving distances [mm]Fig. 8.

**50

B. Results
Figs. 7 and 8 show examples of the trajectory and velocityof the tracing movements. We extracted moving distances(Fig. 7) and velocity peaks (Fig. 8) as feature quantities forthe analysis. We calculated the differences in the feature
quantities for the amplify and reverse conditions with thenormal condition. Figs. 9 and 10 show the averages andstandard deviations of these differences for each condition.
Analysis of the variance showed that the finger’s moving
distances (F0 (1, 394) = 29.7, p = 9.96×10−8 ) and velocity
peaks (F0 (1, 592) = 8.03, p = 0.0048) for the amplify
condition were larger than those under the normal condition
by an average of 7.1 mm and 7.6 mm/s, respectively. For
all participants, the distances tended to be larger than thoseunder the normal condition (Fig. 11). For the reverse condition, the distances (F0 (1, 394) = 7.03, p = 0.0083) andvelocity peaks (F0 (1, 592) = 12.0, p = 0.0006) were also
larger than those under the normal condition by an average of
3.9 mm and 9.7 mm/s, respectively. However these increases
depended on the participants and did not show a uniform
trend (larger for P1, P3, and P5, smaller for P2 and P4). The
velocity peaks for the amplify and reverse conditions showedsignificant differences from those for the normal condition.

30

0

-30

Fig. 11.

Amplify
Reverse5

Reverse–NormalAmplify
Reverse300

Amplify-Normal-20

Differences inPeak velocities [mm/s]

X-axial velocity [mm/s]

Fig. 7.

0

Amplify
Reverse6**

Amplify
Reverse5***
20

Amplify
ReverseX-axial position [mm]

300

P1

P2

P3

P4

P5

Comparison of moving distances for individuals

However their effect sizes were small (d = 0.15 and 0.19
for the amplify and reverse conditions, respectively).
C. Introspective report
The participants reported their introspections in the formof free description and by answering questions after theexperiment.
1) Free description: P1: I felt that the plate was moving
and sliding out of the finger pad. I may have increased thefinger’s normal force in order to keep the plate just beneaththe finger. P2: I felt that my finger’s velocity changed when
the shear deformation was presented. P4: It was difficult to2482

maintain my finger’s velocity to follow the metronome. P5:
Tracing with the device provided me with sensations different
from those obtained when tracing with a bare finger because
the finger contacted the paper by way of a plate.
2) Question form: After the experiment, the participants
experienced the amplify and reverse conditions and answered
the following questions.
Q. Amplify condition: Did you feel a change in friction?
P1: I felt the paper was more sticky, as if my finger had beenslipping the rubber. P2 and P3: I did not feel any changes
in the friction. P4 and P5: I felt that the paper’s frictionchanged.
Q. Amplify condition: Did you feel a change in thefinger’s heaviness or external forces? P1: I felt large shear
deformations of the finger pad caused by the device. I also
felt that my finger moved more quickly than when the
deformation was not applied. P2: I felt that my finger’s
nail was pushed to the moving direction of the finger. P3:
I felt that my finger’s velocity became slow. The finger pad
deformed in an unusual way. P5: I felt the finger to beheavier.
Q. Reverse condition: Did you feel a change in friction?
P1–P3: I did not feel changes in the paper’s friction. P4: I
felt that the paper turned slippery. P5: I felt as if my finger
slid on lubricated glass.
Q. Reverse condition: Did you feel a change in the finger’s
heaviness or external forces? P1: I felt that my finger was
pulled in the direction of the forward movement. P2 and P4:
I felt that my finger received external force. P3: I felt thatmy finger’s velocity became very fast several times. P5: I
may have slowed down the speed of my finger because I felt
my finger was sliding significantly.
D. Discussion
The moving distances under the amplify condition werelarger than those under the normal condition. We attempt
to explain this phenomenon based on a mechanism shownin Sec. II-B where presentation of the additional shear
deformation alters the tracing movements . Under the amplify
condition, when the device presents the additional shear
deformation ∆ds to the finger pad, the coefficient of friction
perceived by the participants increases as shown in (5). They
then feed back the perceived coefficient to their internal
model and generate the augmented finger force, as shown in(6), to maintain their desired finger trajectories. The participants perceived the increased friction by the amplified shear
deformation of the finger pad. Based on such an underlying
mechanism, we speculate that the moving distances of the
tracing movements increased under the amplify condition.
Under the reverse condition, the device applied shear
deformation to the finger pad in the direction of the finger’s
motion, which is implausible for natural physical phenomena. Because the reverse condition was the opposite of theamplify condition, we imagined that the changes in thefinger’s motions would cause dissimilar results to those under
the amplify condition. However, the moving distances of
the tracing movements became larger for three participants(P1, P3 and P5) and smaller for two participants(P2 andP4) compared to the movements for the normal condition.
The influences varied between individuals. Pursuing these
individual variations is a future challenge.
In summary, the amplify condition resulted in increasesof the moving distances for all participants. Three of thefive participants reported increases in the paper’s perceived
friction. The effects of the reverse condition varied forindividuals.
V. EXPERIMENT 2: CIRCULAR TRACEIn Exp. 1, we showed that the presentation of the shear deformation to the finger pad influences the tracing movements
along the axis parallel to the applied shear deformation. In
Exp. 2, we show that it also affects the tracing movements
perpendicular to the applied shear deformation when tracing
a circle.
A. Method
1) Participant: Participants were five right-handed (P1，
P2，P4 and P7) and one left-handed (P6) university students
from our laboratory; we did not include ourselves.
2) Task: The participants traced a circle of 150 mm indiameter for each beat of the 0.5-Hz metronome. They traced
the circle three times in a single trial. At the beginning ofeach trial, they visually confirmed the position of the circle
and placed their fingers on the far bottom of the circle, which
was designated as the starting position.
3) Stimuli: We randomly presented five types of shear
deformations to the participant’s finger pad. Five trials wereconducted for each stimulus. We added two new conditions
to the three conditions used in Exp. 1. The two new conditions presented a shear deformation along the X-axis in

X
Ch1

Ch0

Y

Acrylic
plate

Finger’s
moving direction

a)
ܶ଴
Ch1

Force applied
to finger pad

b)
ܶଵ

Ch0

Fig. 12. Shear deformations to finger pad in circular tracing-task: outercondition2483

where α, Tmax , and Tmin were 5.75×10−3 N s/mm, 1.07 N,
and 0.31 N, respectively, similar to Exp. 1. The variablevy was used in (12) instead of (7) in vx . When the finger
was moved in the negative direction along the Y -axis, as inFig. 12 b), the tensions were given by
T0

=

T1

=

T
(14)
min
T
if
−
10
≤
v
<
0
 min
y

α(|vy | − 10) + Tmin if − 150 < vy ≤ −10 (15)
Tmax if vy ≤ −150.

vy was used in (15) instead of vx in(10).
b) Inner condition: This condition transposed T0 andT1 of the outer condition and presented the shear deformation
inward from the circle.
B. Results
We extracted the moving distances of the trajectories along
the X- and Y -axes as feature quantities for the analysis.
We calculated the differences in the feature quantities forthe amplify, reverse, outer, and inner conditions with thenormal condition. Figs. 13 and 14 show the averages andstandard deviations of the differences for each condition.
Analysis of the variance showed that the finger moving
distances along X-axis (F0 (1, 194) = 11.6, p = 8.17×10−4 )and Y -axis (F0 (1, 194) = 13.0, p = 3.89 × 10−4 ) for theamplify condition were larger than those under the normal
condition by average of 5.8 and 5.7 mm, respectively. For the

Differences in
X–axial moving distances [mm]

***

20

**

0

-20
Amplify-Normal

Reverse-NormalOuter-Normal

Inner-Normal

Average and standard deviation of finger’s X-axial moving

Fig. 13.
distances

***

***

20

Differences in
Y–axial moving distances [mm]accordance with the finger’s velocity along the Y -axis. The
five conditions were as follows:• amplify condition: the finger pad’s shear deformations along the X-axis were amplified
in response to the finger’s X-axial velocity(Fig. 6a),• reverse condition: the shear deformations
along the X-axis were reversed in responseto the finger’s X-axial velocity (Fig. 6b),
• normal condition: the shear deformations were
not presented,• outer condition: deformation was applied outward from the circle in response to the finger’s
Y -axial velocity (Fig. 12), and• inner condition: deformation was applied inward from the circle in response to the finger’s
Y -axial velocity.
a) Outer condition: The motor’s torque was controlled
in response to the finger’s Y -axial velocity. As a result, thedevice applied the deformation outward from the circle. For
example, when the finger moved in the positive direction
along the Y -axis, as shown in Fig. 12 a), the tensions exerted
on the strings of the plate were
 Tmin if 0 ≤ vy < 10
α(|vy | − 10) + Tmin if 10 ≤ vy < 150 (12)T0 =Tmax if 150 ≤ vy
T1 = Tmin
(13)

0

-20

Fig. 14.
distances

Amplify-Normal

Reverse-NormalOuter-Normal

Inner-Normal

Average and standard deviation of finger’s Y -axial moving

individual participants, other than P4 along the Y -axis, thedistances tended to be larger than those under the normal
condition, as shown in Figs. 15 and 16. For the outercondition, the distances along the X-axis (F0 (1, 194) =8.30, p = 4.42 × 10−3 ) and Y -axis (F0 (1, 194) = 24.8, p =1.37 × 10−6 ) were larger than those under the normal
condition by average of 4.7 and 7.7 mm, respectively. For
the individual participants, other than P2 and P4 along
the X-axis, the distances tended to be larger than thoseunder the normal condition. For the reverse condition, thedistances along X-axis (F0 (1, 194) = 0.25, p = 0.6169)
and Y -axis (F0 (1, 194) = 2.24, p = 0.136) did not show
any significant differences from those under the normal
condition. The changes in the moving distances dependedon each participant and did not exhibit a uniform trend.
Finally, for the inner condition, the distances along X-axis(F0 (1, 194) = 0.89, p = 0.3453) and Y -axis (F0 (1, 194) =0.42, p = 0.5154) did not show significant differences fromthose under the normal condition. The distances dependedon each participant and did not exhibit a uniform trend.
C. Discussion
Similar to the linear trace, the circular trace under theamplify condition caused the finger’s moving distances along
the X-axis to become larger than those under the normal condition. This can be interpreted by the mechanism introducedin Sec. II-B. Increases in the distances were also observed
along the Y -axis. We speculate that this was because theparticipants assumed the isotropic frictional properties of thepaper. The participants might have perceived the increases

2484Amplify
Reverse
Outer
Inner

P2

Amplify
Reverse
Outer
Inner

P1

Amplify
Reverse
Outer
Inner

Amplify
Reverse
Outer
Inner

-20

Fig. 15.

P4

P6

P7

Comparison of X-axial moving distances for individuals

R EFERENCES

20

0

Fig. 16.

Amplify
Reverse
Outer
Inner

Amplify
Reverse
Outer
Inner

Amplify
Reverse
Outer
Inner

Amplify
Reverse
Outer
Inner

-20
Amplify
Reverse
Outer
Inner

Differences in
Y–axial moving distances [mm]2), the finger’s moving distances increased for the amplify,
and outer conditions where the deformations were applied
outward from the circle for the later. These results showedthat the presentations of shear deformations to the finger
pad influenced even the finger’s motions perpendicular to theapplied deformations. Further elucidation of the interaction
between the tracing movements and shear deformations of
the finger pad is expected to enhance the development of
human–assistive haptic interfaces.
References are important to the reader; therefore, eachcitation must be complete and correct. If at all possible,references should be commonly available publications.

0

Amplify
Reverse
Outer
Inner

Differences in
X–axial moving distances [mm]

20

P1
P2
P4
P6
P7
Comparison of Y -axial moving distances for individuals

in friction along both the X- and Y -axes. Hence, not only
the X-axial distances but also the Y -axial distances were
influenced by the shear deformations applied by the tactile
device.
We do not interpret the results of the reverse, outer andinner conditions as being based on the mechanism describedin Sec. II-B because these conditions are implausible inour daily lives. However, almost all of the participants
were affected by the presentation of the shear deformations,even though the effects varied for individuals. For the outercondition, the participant’s tracing distances tended to beuniformly increased, which suggests the existence of a
specific mechanism besides the one described in Sec. II-B.
The pursuit of such a mechanism is the next challenge. For
the reverse and inner conditions, the changes in the moving
distances depended on each participant and did not exhibit
a uniform trend.

[1] A. Berthoz, The Brain’s Sense of Movement, Harvard University Press,
pp. 9–11, 21–24, 166–172, 2000.
[2] M. Nakamoto, M. Konyo, T. Maeno, S. Tadokoro, “Reflective Grasp
Force Control of Humans Induced by Distributed Vibration Stimuli
on Finger Skin with ICPF Actuators,” Proceedings of the 2006 IEEE
International Conference on Robotics and Automation, pp.3899–3904,
2006.
[3] R. S. Johansson, G. Westlimg, “Signals in Tactile Afferents from theFingers Eliciting Adaptive Motor Responses during Precision Grip,”Experimental Brain Research, Vol. 66, pp. 141–154, 1987.
[4] H. Kinoshita, “Effect of Gloves on Prehensile Forces during Liftingand Holding,” Ergonomics, Vol. 42, No. 10, pp. 1372–1385, 1999.
[5] J. Watanabe, H. Ando, T. Maeda, “Shoe–Shaped Interface for Inducing
a Walking Cycle,” Proceedings of the 2005 International Conference
on Augmented Tele-existence, pp. 30–34, 2005.
[6] A. Kavounoudias, R. Roll, J. P. Roll, “Specific Whole Shifts Induced
by Frequency-Modulated Vibrations of Human Plantar Soles,” Neuroscience Letters, Vol. 266, pp. 181–184, 1999.
[7] B. E. Maki, S. D. Perry, R. G. Norrie, W. E. Mcllroy, “Effectof Facilitation of Sensation from Plantar Foot–Surface Boundaries
on Postural Stabilization in Young and Older Adults,” Journal ofGerontology: Medical Sciences, Vol. 54A, No. 6, pp. 281–287, 1999.
[8] I. Watanabe, J. Okubo, “The Role of the Plantar Mechanoreceptor in
Equilibrium Control,” Annals of the New York Academy of Sciences,Vol. 374, pp. 855–864, 1981.
[9] V. Levesque, V. Hayward, “Experimental Evidence of Lateral Skin
Strain During Tactile Exploration,” Proceedings of the Eurohaptics,
pp. 261–275, 2003.
[10] W. R. Provancher, N. D. Sylvester, “Finger Pad Skin Stretch Increases
the Perception of Virtual Friction,” IEEE Transactions on Haptics, Vol.
2, No. 4, pp. 212–223, 2009.
[11] W. H. Press, B. P. Flannery, S. A. Teukolsky, W. T. Vetterling,
Numerical Recipes in C: The Art of Scientific Computing, Cambridge
University Press, pp. 650–655, 1992.

VI. CONCLUSIONS
We investigated how the presentation of shear deformation
to the finger pad affects tracing movements. We employedlinear and circular motions as tracing tasks. In the linear trace(Exp. 1), the finger’s moving distances increased when theshear deformation of the finger pad was amplified by the tactile device (amplify condition). Three of the five participants
reported an increase in the perceived friction of the sheet ofpaper they slid their finger on. In the circular trace (Exp.
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