Effects of envelope motion and carrier motion in Gabor patch on perceived position(Summary of Awarded Presentation at the 29th Annual Meeting)

(1)

The Japanese Psychonomic Society

NII-Electronic Library Service

The JapanesePsychonomic Society

The

JaPanese

Jout7:at

of

l]Sychonomic

Science

2011,

VoL

30,No. 1,129-130

Summary

ofAwarded

Presentation1-216

Effects

of

envelope

motion

and

carrier

motion

in

Gabor

patch

on

_perceived

_position

Rumi

HisAKATA,*

Masahiko

TERAo,*

and

Ikuya

MuRAKAMi*

The

Uitiversit),

of

7bleyo*

De

Valois

and

De

Valois

(1991)

showed

that

individuals

_perceive

a shift

in

the

_position

of

a

static

Gabor

patch

with

a

moving

carrier

in

the

direction

of

motion

inside

the

stimulus.

In

our

that

illusory

position

shifts were

induced

in

the

direction

of

carrier

motion

on

the

retina.

Here,

we

investigate

the

effects

ot

envelope

motion

on

the

display

and

examined

_position

shifts when

the

envelope and carrier moved

independently,

The

results revealed

that

the

envelope-relative

motion

rather

than

the

display-relative

motion

induced

illusory

position

shifts.

Key

words:

illusion,

position

perceptton,

visual

motion

perception

The

precise

neural

mechanisms

that

allow

us

to

detect

the

position

ef

an

object

are

still

relatively

unknown.

In

_{psychological}

studies,

the

_perceived

position

of a static object

is

affected

by

motion

inside

that

object.

De

Valois

and

De

Valois

{1991)

showed

that

earrier motion

in

a static

Gabor

patch

induced

a shift

in

the

_perceived

_position

of

the

entire stimulus.

Indeed,

a

number

of

studies

have

used

various

types

of motion

to

induce

an

illusory

position

shift:

carrier

motion

defined

by

binocular

correlation

(Murakami

&

Kashiwabara,

2009),

and

carrier

motion

of

a

plaid

pattern

(e.g.

Hisakata

&

Murakami,

2009).

studies,

however,

have

not

investigated

the

effects

of

envelope

motion

on

perceived

position.

We

previously

showed

that

retinal

carrier

motion

induced

an

illusory

_position

shift when

the

envelope

moved

in

the

same

direction

at

same

speed

as

the

eyes

(Hisakata,

Terao,

&

Murakami,

2010),

In

the

current

study, we examined whether

envelope

mo-tion

affects

the

perceived

position

of an object and whether envelope motion and carrier motion

inter-act,

We

measured

Musory

_position

shifts

while

the

enyelope and carrier moved

independently.

Methods

The

subjects

for

this

study

included

one of

the

authors and seven nai've adults with normal

vision.

*Department _of

_Life

_Sciences,

_The

_University

_of

Tokyo,

3-8-1

Komaba,

Meguro-ku,

Tokyo

153-8902,

Japan

Copyright2011

The

stimuli were

two

vertically arraigned

Gabor

patches

(Fig,1)

presented

on a cathode ray

tube

monitor

(1

min/pix; refresh

rate,

100 Hz).

The

upper and

lower

images

contained a static

horizontal

car-rier

and

a vertical carrier

that

moved at various veLocities.

After

the

lower

Gabor

stimulus

was

pre-sented

for

750

ms,

the

upper

Gaber

stimulus was

presented

for

250 ms.

The

experimental

conditions

were

characterized

by

a

static

envelope

or

a

moving

envelope.

Under

the

static envelope condition,

the

envelopes

of

both

the

upper

and

lower

Gabor

patcbes

were static.

The

carrier

in

the

lower

Gabor

_patch

moved

at

2.5-5

degls.

Under

the

moving

envelope

condition,

both

envelopes

moved

at

2.5 degls

in

the

same

direction

(Fig.1).

In

this

case,

we assessed

display-relative

or

envelope-relative

carrier

velocity.

The

display-relative

velocity

was

determined

based

on

the

carrier

_grating

moving on

the

displayi

-O.5

to

5.5 deg/s

(a

negative

velocity

indicated

that

the

car-rier and envelope moved

in

opposite

directions).

The

enve]ope-relative velocity was

determined

based

on

the

movement

of

the

_grating

relative

to

that

of

the

envelope, and was calculated

by

subtracting

the

en-velope velocity

from

_the

display-relative

velocity:

-3

_to

_3deg/s.

_To

_investigate

_perception

_of

_the

relative

_positions

of moving objects, a control

condi-tion

was used

in

which

both

upper

and

lower

Gabor

patches

were characterized

by

a static

horizental

carner.

We

measured

illusory

_position

shifts using

.

The

Japanese

Psychonomic

Society,

All

rights reserved.

(2)

The Japanese Psychonomic Society

NII-Electronic Library Service

The JapanesePsychonomic Society

130 The

_Japanese

Journa1

of

Psychonomic

Science

VoL30,

No.

1 Figure

1. Two

Gabor

patches

were

_presented

in

lower

visual

fields.

The

fixation

_point

was

prescnted

in

upper

display.

The

carrier

moved at randorn speeds,

stant

methods.

Subjects

were

asked

to

judge

whether

the

upper stimulus was

to

the

right or

left

of

the

lower

Gabor

patch.

Results

Figure

2a

shows

averaged

_positional

shifts

across

subjects under

the

condition

in

which

the

envelope was

static.

We

confirmed

_rhe

illusory

shifts

in

_this

experiment.

The

illusion

saturated at

2.5 deg/s.

Figure

2b

(upper

panel)

shows averaged

_positional

shifts under conditions

in

which

the

envelope moved.

The

lower

axis

indicates

the

envelope-relative

velocity,

whereas

the

upper

axis

indicates

the

display-relative

velocity.

Under

the

control

con-dition,

an

illusory

shift

occurred

even

though

_the

two

carriers

did

not move.

This

likely

reflected

positional

shifts caused

by

temporal

differences

be-tween

the

uppcr and

lower

Gabor

patches,

similar

to

flash-lag

effects.

To

extract

_positional

shifts only

by

stimulus

motion,

we

subtracted

the

shift

from

the

other

data

{Fig.

2b,

lower

panel).

The

illusion

was related

to

the

envelope-relative motion, not

the

dis-p]ay-relative

motion.

Furthermore,

we

found

that

the

magnitude of

the

_position

shifts

decreased

when

the

carrier

and

envelope

moved

in

the

same

direc-tion,

compared with conditions

in

which

they

rnoved

in

opposite

directions

(compartson

of

absolute

val-ues:

F(4,

20)=3.66,

p<O.05).

Discussion

In

this

study,

we

showed

illusory

_positlon

shifts

in

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Figure

2. (a)

The

averaged

_position

shifts

in

static envelope condition

inter

subjects,

{b)

The

averaged

_position

shifts

in

moved

velope

condition,

Positive

illusion

indicated

that

the

envelope was apparently shifted

in

the

same

direction

as

the

envelope and

tive

values

indicated

_that

the

envelope

appeared

to

shift

jn

opposite

direction

to

the

envelope motion.

Lower

_panel

showed

the

illusions

after

subtracting

the

magnitude of

illusion

in

herizontal

condition.

Errer

bars

indicated

the

standard

errors.

the

direction

of carrier motion relative

to

the

enve-lope,

even

if

the

enve]ope of

the

stimulus moved.

We

also

found

that

the

magnitude of

the

illusory

shifts

decreased

when

the

envelope and

carrier

moved

in

sarne

directions.

These

results suggest

that

the

posi-tion

of

a

stimulus

is

_primarily

estimated

based

on

the

contour

position

and

this

estimation

is

biased

by

motion

inside

the

stimulus object.

In

addition,

the

estimated

position

of

the

object

is

disproportionately

opposite

to

the

direction

of contour motion

because

the

future

stimulus

position

is

unknown.

References

De

Valois,

R. L.,

&

De

Valois,

K,

K. (1991).

Vernier

acuity

with

stationary

moving

Gabors.

Vision

Re-search,

31(9),

1619-1626.

MurakamL

I. &

Kashiwabara,

Y. _(2009>.

Illusory

tion

shifts

induced

by

cyclopean

motion.

Vision

Research,

49"5L

2037-2043.

Hisakata,

R. &

Murakami,

I. _(2009>,

Illusory

position

shifts

induced

by

_plaid

motion.

Vision

Research,

49 (24),

2902-2910.

Hisakata,

R. Terao,

M,,

&

MurakamL

L

(2010).

Iope

motion

affecting

a

motion-induced

position