Effects of spatial factors on tactile roughness perception : A study based on signal detection theory(Summary of Awarded Presentation at the 31st Annual Meeting)

The Japanese Psychonomic Society

NII-Electronic Library Service

The JapanesePsychonomic Society

TheJltpanesefourna[ofPsychonomicScience

2013,VbL32,No.1,13].]32

Summary

of

Awarded

Presentation

Effects

of

spatial

factors

on

tactile

roughness

_percep

A

study

based

on

signal

detection

theory

-tlon

Seiya

KAKIzAKI*,

YUika

SuzuKi,

and

Jiro

GyoBA

Ibhoku

U}iiversity

Our

previous

studies

demenstrated

that

spatial

facters,

such as

finger

_position

{hand

_posture)

and

distance

from

the

stimulated

finger

te

the

head

modulate

tactile

roughness

_perception.

Herein

we

investigate

whether spatial

factors

influence

the

sensitivity

or response

bias

ef

tactile

reughness

discriminatien

using signal

detection

tech-niques,

Participants

were asked

to

discriminate

the

roughness of

two-sided

stimuli

between

twe

fingers

in

a variety

of

postures.

When

the

stimuli were

_presented

close

to

the

head,

the

discrimination

sensitivity

for

the

finger

located

on

the

back

surface of

the

stimuli was

lower

than

that

for

the

finger

on

the

front

surface.

Furthermore,

judgments

by

the

finger

on

the

back-side

were

biased

toward

the

same

direction

as

the

roughness ef

the

front

surface regardless

ef

the

distance

of

the

hand

from

the

head.

These

results

indicate

that

spatial

factors

differently

modulate

the

sensitivity and

the

response

bias

ofroughness

discrimination.

Key

words:

touch,

roughness

discrimination,

_peri-head

space, sensitivitF response

bias

Our

preyious

study

found

that

when

_participants

were asked

to

discriminate

the

roughness ofone side of a

two-sided

abrasive

_paper

_pinched

with

the

thumb

and

index

finger,

the

discrimination

ability was

impaired

especially when

the

dis-tractor

was

the

inside

relative

to

the

head

rather

than

the

out-side of

the

two

sides of stimuli

(Kakizaki,

Suzuki,

&

Gyoba,

2011).

In

addition,

this

effect was observed only when

the

hand

was

located

in

the

peri-head

space,

Herein

we aim

to

clarify whether spatial

factors

modulate

the

sensitivity or re-sponse

bias

of

tactile

roughness

discrimination

using

signal

detection

analysis.

We

conducted

two

experiments

in

which

the

stimulus signal was rougher or smoother

than

the

noise signaL

Methods

Participants

IXvelvegraduateandundergraduatestudents

participated

both

in

Experiment

1

and

Experiment

2,

Stimuli

Each

stimulus was a

thick

_paper

(3X9

cm) with

abrasive

_paper

(3

×

6

cm) attached

to

both

sides,

The

_grit

val-ues of

the

abrasive

_papers

were

#4000

(average

particle

size of

3

_gm:

smoother stimulus) and

#1200

(12

_"m:

rougher

stimu-lus).

The

smeother

(rougher)

stimulus was regarded as

the

signal

(noise)

in

Experiment

1

and vice versa

in

Experiment

2.

*

Corresponding

author.

Department

of

Psychology,

Graduate

School

of

Arts

and

Letters,

Tbhoku

Universitp

27-1

Kawauchi,

Aoba-ku,

Sendai

980-8576,

Iapan

E-mail:thedevilishlefty@yahoo,co.jp

The

distractor

stimulus was

the

same

(noise)

throughout

the

experiment,

The

target

stimulus was either

the

signal

in

the

SN

condition or

the

noise

in

the

NN

condition

(Fig.

IA).

Procedure

Participants

sat on a chair and

_placed

their

chins on

the

chin-rest,

They

were

blindfolded

by

eye-masks

and wore

headphones

through

which white noise

(5S

dB)

was

delivered

during

the

experiment.

They

pinched

a

two-sided

stimulus with

their

right thumb and opposing

index

finger.

Their

fingertips

_pointed

toward

the

left.

The

stimuli were moved

6

cm

toward

their

fingertips

by

an experimenter at a speed ofapproximately

4

cmls.

Stirnuli

were

_presented

near or

far

from

the

head

(12

cm or

'

50

cm

in

front

of

the

base

of

the

_participant

snese,

Fig.

IB).

The

_participants

were randomly

divided

into

two

_groups

with respect

to

the

side

of

the

target

stimulus

that

was assigned

to

the

index

finger

or

thumb.

AccerdinglM

the

_participants

in

one

A

SNcondition

si;x･･as,ggeei.,asma

Tar etslde/ Distractersidesfieswel,

cepy

ag'ng'$leeesX$iewname

B

t-me･ttt/

NN

conditian

Figure

1.

Configuration

oftactile stimuli

(A)

and

tion

ofstimulus

_presentation

(B).

right

2013.

TheIapanese

Psychonomic

Society

All

rights reserved.

The Japanese Psychonomic Society

NII-Electronic Library Service

TheJapanesePsychonomic Society

132

The

_Japanese

_Journal

of

PsychonomlcScience

Vbl.

32,

No.

1

group

were

asked

to

_judge

the

roughness of stimuli

_presented

tothe thumb

{thumb

_group),

while

the

other

_greup

responded

to

the

stimulus

_presented

to

the

index

finger

_(index

finger

group).

The

participants

were

then

instructed

to

verbally

judge

whether

the

roughness of

the

stimulus on

the

target

side

was

`smoeth'

or

'rough'.

The

judgrnent

ofeach

trial

was scored

as either a

hit

or rniss

in

the

SN

condition and correct

rejec-tions

or

fhlse

alarms

in

the

NN

condition.

Forty

trials

were

conducted

for

each of

the

eight conditions, which consisted of

stimulus

_position

(nearlfar

from

the

head)

×

type

of stimuli

(SNINN)

× side

of

target

stimuli

(inside/outside

relatively

to

the

head).

Results

For

each

_participant,

the

d'

_{(discrimination}

sensitivity)

and

c

(response

bias)

in

each condition were calculated and

ana-lyzed

using

two-way

repeated

ANOXCAs

with

distance

(nearl

far)

×

target

side

(insideloutside)

as

factors

(Fig.

2).

Regardless

of

the

condition,

the

thumb

and

index

finger

_groups

did

not

differsignificantly

The

d's

had

significant main effects

for

_the

_target

side

CExp.

1:

F(1,

11)==42.85,

_p<.OOI;

Exp.

2:

F(1,

11)=6.65,

_p<.05)

and significant

distanceXtarget

side

interactions

(Exp,

1:

F(1.

11)=17,90,

_p<.O05;

Exp.

2:

F(1,

11)=13,27,

_p<.O05).

Post

hoc

comparisons reveared

that

the

sensitivity scores

in

the

near cendition

were

higher

in

the

inside

condition

than

that

in

the

outside

condition

(Exp.

1:

ps<,e05;

Exp.

2:

Ps<,OOI),

The

cs

had

main effects

for

the

target

side

(Exp.

1:

F(1,

11)=33.67,

_p<.OOI;

Exp.

2:

F(1,

11)=31.61,p<.OOI)

and significant

distance

Xtarget

side

interactions

(Exp.

1:

F(1,

11)=5.79,

_p<.05;

Exp

2:

F(1,

11)=5.46,

_p<.05).

Post

hoc

comparisons revealed

that

the

_judgments

in

the

outside cendition were

biased

toward

the

rougher

(Exp.

1:

ps<.el)

and srnoother

(Exp.

2:

_ps<.e05)

sides

than

those

in

inside

condition, suggesting

that

the

biases

in

the

outside conditions

were

in

the

same

direction

as

the

distractors'

roughness.

Furthermore,

only

in

the

eutside condition was

the

bias

in

the

near condition stronger

than

that

in

the

far

condition

(Exp.

1:ps<.O05;

Exp,

2:ps<,10).

3e

.:f'

',･ll::1:

l

s.s ],o 1.5 1.0a' L5 1.0 D.5 DO '-'p<

afrth

1:nside

Miaj'

insitie o-tstael

/ 1 N{tr _/ Ftr _i

t----i-l

.OOL

+"p<.OOS Rougn --"

T

OIS

-OIO

-ots

,

t o.w 1 ,l./e;,i'll/ag,side.,,

/ "p

.t

.Ol

_ti)(.10

4--Expeliment1

1ottwdFnrrl' Smooth

1

oli omo o,ts,

:NIO

l

om "os oco O,ISRotigh

[

Mi-Jfi]

oeNdtlasnte

--l-.

imulFer

I

Experiment2

Figure

2.

Mean

d'

(left)

andc

(right)

in

Experiment

1

(above)

and

Experiment

2

(below).

Errer

bars

indicate

the

standard errors ofthe means,

Discussion

We

investigated

the

effects

of

spatial

factors

on roughness

discrimination

tasks

when

_participants

_grasped

double-sided

abra$ive

_paper

between

their

thumb

and

index

finger,

When

the

_participants

discriminated

the

stimuli

in

their

_peri-head

space,

the

discrimination

sensitivities on

the

outside

finger

were

lower

_than

those

on

the

inside

finger.

In

addition,

the

analyses

for

the

response

bias

revealed

that

the

distractor

on

the

inside

finger

misled

judgments

of

the

outside

finger

irre-spective of

the

distance

from

the

head,

although

the

degree

of

the

response

bias

changed

depending

on

the

distance

from

the

head.

In

summarM

the

response

bias

toward

the

inside

stirnuli

was smaller as

the

distance

frorn

the

head

was

larger,

while

the

discrirnination

sensitivity on

the

outside

finger

decreased

only

in

the

_peri-head

space.

Reference

Kakizaki,

S.,

Suzuki,

Y/,

_&

_Gyoba,

_J.

_(2011).

_Dominance

of

tac-tile

reughness

on

the

inside

finger

depends

on

the

distance

from

the

head.

The

30th

Annual

Meeting

of

the

_ippanese