Perception of motion trajectories of objects from moving cast shadows in human (Homo sapiens) infants, Japanese macaque (Macaca fuscata) infants, and an adult chimpanzee (Pan troglodytes)(Summary of Awarded Presentations at the 24th Annual Meeting)

The Japanese Psychonomic Society

NII-Electronic Library Service The JapanesePsychonomic Society

TheJopaneselburnalofRsychonomic Science 2006,V'ol,2;-,,No, 1,l21-122

2P39

Perception

of

motion

trajectories

of

objects

from

moving

cast

'

tt

shadows

in

human

(Homo

saPiens)

infantsi

_,Japanese

macaque

(Macaca

fuscata)

infants,

and

an

adult

chimpanzee

(Pan

trogtodytes)i)･2)

Tomoko

IMuRA*･

**,

Masaki

ToMoNAGA***,

Masami

K.

YAMAGucHI****,

and

Akihiro

YAGi*

Kwansei Gahuin University*,

ltipan

Society

for

the

Promotien

of

Science**.

thimate

Research institute,

Klyoto

Liniversit3,***,

and

Chuo

Uitiverstty****

We

investigatcd

theperception ofmotion trajectoriesof objects from moving cast shadows by

human

and macaque infants,and an adult chirnpanzee, using a

habituation-dishabituation

prQce-dure. We testedthe ability to discriminate

between

a "depth" _display

which contained a bal!a'nd

a cast shadow moving

diagonaily,

and an "up"

display

containing a ball with a

diagonal

trajectory and a cast shadow with a horizonta]trajectory,The results suggest thattheability toperceive the

' metion trajectoriesof the objects

from

meving cast,shadows was shared

by

the three _pnmate

'specles.

Key

words: cast shadow, pictorial

depth,

infants,humans, chimpanzees,

Japanese

macaqucs

The

present study examined the ability of three

differenttypes of subjects to

distinguish

the

motion

trajectoryof an object from a moving cast shadow.

Human

infants

aged

from

4

to

7 months,

Japanese

macaque infantsaged 5months and an adult

chim-panzee participatedinthestudy.

A

cast shadow can

be one of pictorial

depth

cues and

it

provides a

three-dimensional spatia! layout of objects

in

two-dimensional

pictures

CImura

et al.

2006),

The

results were

discussed

from a comparative-developmental

viewpoint,

* _{Department of Psychology,}

Kwansei

Gakuin

University,

1-1-155

Uegahara,

Nishinomiya,

Hyogo 662-8501

**

_Japan

_{Society forthe}

_Prornotion

_of

Science

***

_Language

_and

_Intelligence

_Section,

_Primate

Research Institute,Kyoto

University,

yarna,Aichi 484-8506

****

_Department

_{of Psychology,}

Faculty

of

Literature,

Chuo University,742-1

nakano,

Hachiohji,

Tokyo 192-0393

Japan

i'A _part of thisreport

has

been

published

in

Imura et al,

(2006),

2) Supported by MEXT

grants

(nos.

120022009,

15500172,

16002001).

Copyright2006. The JapanesePsychonomic Society

Method

Participants There were three types of

partici-pantsinExperiment

1:

human

iniants

aged at from 4

to

5

months

{N=

12,mean age =

135.9

days)

and

6

to

7 months

(N=12,

mean age==197.9 days);

Japanese

rnacaque

infants

aged 5 months

(N=8,

mean age==

141.6

days);and one adult chimpanzee

(22

_yearsold),

The

participantsof Experiment 2 were

hurnan

in-fantsaged

from

4

to

5

months

(N=12,

mean age==

149.0 days) and

6

to

7

months

(IV=12,

mean age=

196.7

days),

Stimuli

Figure la shows an exarnple of the

stim-uli used inExperiment 1,We _prepared two kinds of

displays,

One

display

was perceived

by

human

adults as movernent in

"depth",

and contained a ball

(subtending

3 degreesX3 degrees of visual angleL

and a cast shadow

(subtending

3

degrees×1degree of visual angle) with

diagonally

trajectories on the

floor,

The other display was perceived as flowing

"up",

and contained a ballwith a

diagonally

trajec-tory,

and acast shadow with a horizontal trajectory

en the fioor, Figure

lb

shows an example of the

stimuli used inExperiment 2. The spatial

relation-ship

between

a

ball

and a shadow was reversed to

The Japanese Psychonomic Society

NII-Electronic Library Service The JapanesePsychonomic Society

122

(a)

Experiment

t:up

The

Japanese

Journal

of Psychonomic Science V

(c)

20 18:. 16.I t4i'

l::8l,::

(b)Experi"yent

2/norup -up

,ssdepth

oL 25,

No.

1

1

Figure

1, Examples of the stimuli used in

Experiment

1{a)and Experiment 2(b), The

mean ]ooking times

during

the testtrialsfor

humans, macaques, and a chirnpanzee in

periment 1(c).

that used

in

Experiment

1

_<that

is,"no-depth"

and

"no-up"

displays). These

displays

did

not

_produce

three-dimensional

impressions

for

human

adults.

A

balland a cast shadow moved back and forthat a

constant velocity of 8.13deg/sec.

Procedure

Thehabituation-dishabituationproce-dure was used

in

both

experiments, The

experimen-tal session consisted of four habituation

tria]s

and

two testtrials.For humans, the

duration

of a

ha-bituation

trialwas controlled

by

_the

looking

behav-iorof the infants,

A

trialwas terminated when an

iniant

looked

away from themonitor formore than 2

seconds or continued to look

for

up to

40

seconds.

Thc

duration of each testtrialwas fixedto 20

sec-onds. For the macaques and the chimpanzee, the

duration

of each

habituation

and test

tr{al

was

fixed

to 20 seconds. The chimpanzee was testedfor 9

sessions intotal

_(one

session _per month), The order ef the test

display

was counterbalanced. In

Experi-ment

1

_the

_participants

were habituated to the

"'depth"

display, and then _tested with the novel

"depth"

and "up" _displays.

In

Experiment 2 they

were habituated _{to the}"no-depth"

display,and then

testedwith _the "no-up"

and "no-depth"

disp]ays.

It

was _predicted that ifall of _{the participants}

(in

_the

same manner as the human adults} _perceived

_the

habituation

display

as a motion indepth,then they

would show a significant novelty _{preierence tothe}

"up"

display

in

Experiment

1.

In

addition,

if

such a preference to the "up"

display

inExperiment 1was

exp]ained by a three-dimensional impression, they

were expected toshow a novelty response toboth

displays

during thetest.

Results

and

Discussion

The mean looking times during the _{testtrialsfor}

the three species inExpcriment

1

are

illustrated

in

Figure

lc. During the test the "up" _display

was

looked longer than the

"depth"

display

by

both

the6 to

7

months

human

infants

(t(11)=2,30;

_p<.05 twc)

tailed)and the 5 month monkey

infants

(t(7)=2.52;

p<.05,

two-tailed),

Although

the data was

from

a

single subject, the adult ehirnpanzee a]so

demon-strated atendency similar _tothe

human

and monkev

infants

_(t(8)=1.89;

_p<.05,

one-tailed). The findings

from Experiment

1

suggest thathuman infantsaged

6 to

7

months, and

Japanese

macaques aged 5

months, discriminated the motion trajectoriesof the

ballswhen using acast shadow cue. Incontrast,

both

age _groups of

human

infants

did not exhibit a

sig-nificant novelty preference between the "no-up"

and

"no-depth"

displays in

Experiment

2.

These results

suggest that the 6 to7month

_pld

human infantsin

Experiment

1

discriminated

the two displays

by

a

three-dimcnsional

depth

impression,

Taken

to-gether,the _perception of

depth

from

a cast shadow

was shared by the _threeprimate species.

The

find-ings might suggest that the _perception of pictorial

depth

is

tosome extent biologically

determined,

and

has

been

acquired

during

_the course of _primate

evo-lution.

Reference

Imura,

T. Yamaguchi,

M.

K.

Kanazawa.

S.Shirai,N.

Otsuka, Y. Tomonaga,

M.

&

Yagi,

A. 2006

Percep-tjonof motion _trajectoryof object from the

ing cast shadow

in

infants,

Viz'sionResearch,

46,

652-657.