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Journal
of
Comparative Psychology
1999, Vol.
113,
No. 4,
347-364
Copyright
1999
by the
American Psychological Association,
Inc.
0735-7036/99/S3.00
Dolphins
(Tursiops
truncatus}
Comprehend
the
Referential Character
of
the
Human Pointing Gesture
Louis
M.
Herman
University
of
Hawaii
at
Manoa
and
Kewalo
Basin Marine Mammal Laboratory
Sheila
L.
Abichandani,
Ali N.
Elhajj,
Elia
Y. K.
Herman,
and
Juliana
L.
Sanchez
Kewalo
Basin Marine Mammal Laboratory
Adam
A.
Pack
Kewalo
Basin Marine Mammal Laboratory
and The
Dolphin Institute
The
authors
tested
a
dolphin's
(Tursiops
truncatus) understanding
of
human manual pointing
gestures
to 3
distal objects located
to the
left
of, to the right of, or
behind
the
dolphin.
The
human
referred
to an
object through
a
direct point
(Pd),
a
cross-body point
(Px),
or a
familiar
symbolic gesture
(S).
In
Experiment
1,
the
dolphin responded correctly
to 80% of Pds
toward
laterally placed objects
but to
only
40% of Pds to the
object behind. Responding
to
objects
behind
unproved
to 88% in
Experiment
2
after exaggerated pointing
was
briefly instituted.
Spontaneous comprehension
of Pxs
also
was
demonstrated.
In
Experiment
3, the
human
produced
a
sequence
of 2
Pds,
2
Pxs,
2 Ss, or all
2-way
combinations
of
these
3 to
direct
the
dolphin
to
take
the
object referenced second
to the
object referenced
first.
Accuracy ranged
from
68% to 77%
correct (chance
=
17%).
These
results
established
that
the
dolphin
understood
the
referential character
of the
human manual pointing gesture.
Manual
pointing
(use
of the
deictic gesture)
by
humans
serves
to
call another's attention
to an
object,
an
event,
or a
place
of
interest
to the
pointer.1
Human pointing
is
thus
a
social
triadic
transaction, involving
the
coordination
of the
attention
of the
pointer
and the
observer
to the
same target
or
event.
Implicit
in
adult human pointing behavior
is not
only
the
intent
to
manage
the
attention
of
another individual
but
also
an
expectation that
the
individual understands
the
referring
function
of the
pointing behavior. Likewise,
the
human
observer understands
the
intent
of the
pointer
to
direct attention toward
a
particular object, event,
or
place.
The
understanding
of the
referential
function
of the
Louis
M.
Herman, Department
of
Psychology, University
of
Hawaii
at
Manoa
and
Kewalo Basin Marine Mammal Laboratory,
Honolulu, Hawaii; Sheila
L.
Abichandani,
Ali N.
Elhajj,
Elia
Y. K.
Herman,
and
Juliana
L.
Sanchez, Kewalo Basin Marine Mammal
Laboratory, Honolulu, Hawaii; Adam
A.
Pack, Kewalo Basin
Marine Mammal
Laboratory,
Honolulu,
Hawaii,
and The
Dolphin
Institute, Honolulu, Hawaii.
Ali
N.
Elhajj
is now at the
Department
of
Psychology, University
of
Hawaii
at
Manoa.
Elia
Y. K.
Herman
is now at the
Independent
Studies Concentration, Brown University.
This project
was
funded
in
part
by
grants
from
Earthwatch
and
its
Research
Corps;
by financial
support
from
The
Dolphin
Institute;
and by
equipment donations
from
Apple Computer,
Inc.,
and
Mitsubishi,
Inc.
We
thank
the
staff,
students, interns,
and
volunteer
participants
at
Kewalo Basin Marine Mammal Laboratory
who
contributed
to
this
project.
We are
grateful
to
Matthias
Hoffmann-Kuhnt,
who
pre-
pared
the
computer images from
the
digital
videotape
record.
Correspondence concerning this article should
be
addressed
to
Louis
M.
Herman, Kewalo Basin Marine Mammal Laboratory,
1129
Ala
Moana Boulevard, Honolulu, Hawaii
96814.
Electronic
mail
may be
sent
to
lherman@hawaii.edu.
human
manual pointing gesture follows
a
developmental
progression
in
infants.
Lempers (1979) noted that beginning
at
9
months
of
age,
infants
were able
to
direct their attention
to
objects
50 cm
from
the
extended
arm and
index
finger
of
an
adult
but did not
understand points
to
objects
at a
distance
of 2.5
m
until
the age of 12
months. Lempers
thus
distinguished
between
prereferential
comprehension,
hi
which
the
object
and the
pointing
finger
must
be
close together,
and
referential
comprehension,
in
which
the finger can be
distant
from
the
object.
Butterworth
(1991)
and
Butterworth
and
Grover
(1988,
1990)
reported
findings
similar
to
those
of
Lempers:
Infants
younger than
12
months usually only
looked
at the
extended
finger or at
objects near
it
(see
also
Desrochers,
Morissette,
&
Ricard,
1995),
but
beginning
at
about
12
months, they could
follow
the
direction
of the
pointing
finger
toward more distant objects. Furthermore,
at
15
months,
infants
were able
to
disregard nearby objects
in
the
path
of the
point
to
look
at
more distant objects.
Morissette, Ricard,
and
Decarie
(1995)
generally
confirmed
this
progression, although they
found
a
somewhat longer
developmental
period.
At 12
months,
infants
attended primar-
ily
to
objects close
to the
pointer's hand. Attention
to
more
distant objects
did not
emerge until approximately
15
months
of
age.
The findings of
Morissette
et
al.
were based
on
a
longitudinal
study,
whereas those
of
Butterworth
and
Grover
were based
on a
cross-sectional approach.
In
addi-
tion,
Morissette
et al.
considered
nonresponses
by the
infants
(trials
on
which
the
infants
offered
no
response
to the
adult's
point)
as
incorrect, whereas Butterworth
and
Grover
ex-
cluded nonresponses
from
their data.
The
more complete
data
set of
Morissette
et al. and the
greater control over
1
For a
general discussion
of
deictic
expressions
in
human
language,
see,
for
example, Anderson
and
Keenan
(1985).
347
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