2-B-15 コントラストの変化によって生じる奥行き運動知覚(2002年度 日本基礎心理学会第21回大会優秀発表賞)

The Japanese Psychonomic Society

NII-Electronic Library Service

The JapanesePsychonomic Society

The

fopanese

Jbumat

of

I)sychonomic

Seience

2003,

VoL

22,

No.

1,49-50

Prizewinner's

Summary2-B-15

The

effect

of

contrast

change

on

the

motion-in-depth

_perception

Norimichi

KITAGAwA,*

Hiromi

AKuTsu,**

and

Shigeru

IcHmARA**

IVihon

U)liversity*

and

Tolayo

Mbtrmpolitan

Uhiversiby**

Contrast

is

a

cue

for

depth

_perception;

the

farthcr

away

an

object

is,

the

less

contrast appears

in

thc

surface

_plane.

What

happens

if

the

contrast

of an object varies

in

tirne?

Do

we

_perceive

the

object moves

in

depth?

Wc

examined

whether

a

contrast

change

induccs

motion-in-depth

perception.

The

stimulus

was

a

circular

sine wave

_grating

of

1

s

duration

whose

phase

was shifted

by

various angles every

250

ms.

The

contrast

of

the

grating

cither

decreased

remained constant.

or

mcreased.

The

subjects

judged

whether

the

stimulus appearcd

to

move

towards

them,

or

away

from

them.

When

thg

contrast

of

the

stimulus

decreased

_(increased)

the

number ef 'receding'

Clooming')

responses

increased.

The

resu]ts suggcst

_that

a

contrast

change

_produces

motion-in-depth

perception.

Key

words:

contrast

change,

motion-in-depth,

size change, visien

For

static

depth

_perception

there

is

mounting

evi-dence

that

the

human

visual

system

has

the

ability

to

estimate

the

depth

from

_the

contrast

{Ichihara

et al. submitted;

Ashley,

1898).

To

our

knewledge

however,

the

contribution of a contrast change

to

the

perception

of a

dynamic

event

has

not

been

exam-ined.

In

the

_present

study we examined whether a change of

contrast

could

induce

the

_perception

of motion-in-depth.

To

assess

the

contribution of

a

contrast

change

to

motion-in-depth

_perception,

we used a stimulus which

induces

an

apparent

size

change,

If

the

contrast

change

could

induce

a

per-ception

of

motion-in-depth

then

the

change

in

con-trast

would

cancel

the

impression

of motion-in-depth

which

was

induced

by

the

apparent

sjze

ehange.

Methods

The

stimuli were circular sine

wave

_gratings

of

1

s

duration

(Figure

la).

The

spatial

frequency

of

the

gratings

was

1,56

c/deg,

the

size of

the

stimulus was

9

degrees

of

visual

angle

and

the

average

luminance

of

the

stimulus

was

kept

constant at

60

cd/m2.

The

contrast of

the

_grattngs

either

decreased,

remained constant or

increased

exponentially

between

O,Ol

and

O,6,

The

_phase

of

the

_gratings

was shifted

by

either

120,

150,

180,

210,

or

240

every

250

ms.

The

*

_Department

_of

_Psycholegy,

_Nihon

_University,

25-40,

Sakurajosui,

Setagaya-ku,

Tokyo

8550

amount

of

the

shift

below

_(over)

180

_produced

an

apparent motion of expansion

(contraction).

Each

stimulus was

_presented

50

times

in

a

random

order.

Five

stuclents

_participated

in

_the

experirnent,

All

had

norrnal

or corrected-to-normal vision.

The

sub-jects

were asked

to

fixate

on

the

center

of

the

stimuli

and

to

judge

whether

the

stimulus

appeared

to

move

towards

them,

or

away

from

them.

The

experiment

was

conducted

with

binocular

vision

in

a

dark

room,

Results

and

Discussion

We

found

that

the

change of contrast

influenced

the

judgment

of

the

motion-in-depth

direction

(Fig-ure

lb).

When

the

contrast

decreased,

the

`receding' responses

increased,

resulting

in

a

psychometric

function

which

shifted

towards

the

left

relativc

to

the

function

of

the

constant condition.

On

the

oth-er

hand,

when

the

contrast

increased,

the

function

shifted

towards

the

right.

The

function

for

the

con-stant

condition

was

located

between

the

decreasing

and

increasing

conditions,

These

trends

were

ob-served

for

all of

the

subjects

except

for

NA.

To

quantitatively

analyze

the

effect

of

the

contrast

change

we

calculated

the

null

_points,

that

is,

the

angle of

the

phase

shift at which

the

_probability

of

a

Lreceding'

response was

O.50.

A

one-way

ANOVA

with

the

contrast-change

direction

as a

within-$ubject

factor

showed

a

significant main effect

{F(2,

8)

==

10.42;P<

O.Ol),

A

_posterior

_pairwise

_comparison

The Japanese Psychonomic Society

NII-Electronic Library Service

TheJapanesePsychonomic Society

50

a

os O.4 O,2 o O,6thtu O,4t[eO o. o O,6 O,4 O.2

The

Japanese

Journal

of

Psych

(Tukey's

Honestly

Significant

Difference,

P<

O.O

1}

m-dicated

a significant

difference

between

the

mean

for

the

decreasing

condition

(175,13)

and

that

for

the

increasing

condition

(193.80).

But

the

differences

between

the

mean

values

of

cither

of

these

two

con-ditions

and

the

constant condition

(183.40)

were

not

significant.

The

apparent

motion

of

cxpansion

(contraction}

was canceled

by

the

decreasing

(increasing>

contrast.

The

results suggest

that

contrast

change

_produces

directly

motion-in-depth

_perception

and

that

the

hu-man visual

system

integrates

the

contrast

informa-tion

to

achieve

_perception

of rnotion-in-depth.

An

alternative

_possibility

is

that

a change of contrast

indirectly

contributes

to

motion-in-depth

_perception,

onomlc

$saerege?.=o-g9tr

Science

Vol,

22,

No.

1

o 2so sco 7so deoo

Time

(m$)

1?O 150 1en 210 240 1ee ri50 1ee 210 240

Ameunt

of

_phase

shift

(deg)

Figure

1,

(a)

The

visual stimuli

used

in

thc

cxperiment.

The

abscissa and ordinate

indicate

the

time

and

the

contrast,

respectively.

The

thick

white

lines

indicate

continuous contrast changc

over

time.

The

top,

middle and

bottom

panels

indicate

the

stimuli

with a contrast which

decreased,

remained

constant,

and

increased,

respectively,

The

stirnuli with

a

_phase

shift

of

180

are

shown.

Four

panels

on each row show

the

stimuli at

O,

250,

500,

and

750

ms.

_(b)

The

_proportion

of `receding'

responses as

a

function

of

the

phase

shift.

The

results

for

individua]

subiects

are

shown.

For

all

of

the

subjects,

except

for

NA,

thc

psychometric

function

shMed

towards

the

left

(righO

when

the

contrast

decrcased

(increased),

b---Decreasing

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'fr''"t;/

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-t-tt

In

our

_prelimmary

experiment

we

observed

that

when we used

phase

shifted

stimulL

a

contrast

change

had

a strong effect on

the

motion-in-depth

perccption.

But

the

effect

of

the

contrast change was weak when

we

used

static

phase

stimulL

The

contrast

change

_rpay

therefore

induce

an apparent

change

in

size and

then

the

apparent motion

may

'

induce

the

motion-in-depth

perception.

References

Ichihara,

S.,

Kitagawa,

N.

&

Akutu,

H,

{submitted)

Contrast

of

a

random

dot

_pattern

induces

depth

perceptlon.

Ashley,

M.L.

1898

Concerning

the

significance

of

intensity

of

light

in

visual estimates of

clepth.