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JOURNAL
OF
THE
EXPERIMENTAL
ANALYSIS
OF
BEHAVIOR
STIMULUS
CONTROL
IN
THE
USE
OF
LANDMARKS
BY
PIGEONS
IN
A
TOUCH-SCREEN
TASK
KEN
CHENG
AND
MARCIA
L.
SPETCH
UNIVERSITY
OF
TORONTO
AND
UNIVERSITY
OF
ALBERTA
Pigeons
were
tested
in
a
search
task
on
the
surface
of
a
monitor
on
which
their
responses
were
registered
by
a
touch-sensitive
device.
A
graphic
landmark
array
was
presented
consisting
of
a
square
outline
(the
frame)
and
a
colored
"landmark."
The
unmarked
goal,
pecks
at
which
produced
reward,
was
located
near
the
center
of
one
edge
of
the
frame,
and
the
landmark
was
near
it.
The
entire
array
was
displaced
without
rotation
on
the
monitor
from
trial
to
trial.
On
occasional
no-reward
tests,
the
following
manipulations
were
made
to
the
landmark
array:
(a)
either
the
frame
or
the
landmark
was
removed;
(2)
either
one
edge
of
the
frame
or
the
landmark
was
shifted;
and
(3)
two
landmarks
were
presented
with
or
without
the
frame
present.
On
these
two-landmark
tests,
the
frame,
when
present,
defined
which
was
the
"correct"
landmark.
When
the
frame
was
absent,
the
"correct"
landmark
was
arbitrarily
determined.
Results
showed
that
pecks
of
2
pigeons
were
controlled
almost
solely
by
the
landmark,
pecks
of
3
were
controlled
primarily
by
the
landmark
but
the
frame
could
distinguish
the
correct
landmark,
and
1
bird's
behavior
was
controlled
primarily
by
the
frame.
Stimulus
control
in
this
search
task
is
thus
selective
and
differs
across
individuals.
Comparisons
to
other
search
tasks
and
to
other
stimulus
control
experiments
are
made.
Key
zwords:
stimulus
control,
search,
landmarks,
spatial
learning,
attention,
peck,
pigeon
Many
animals
use
visual
landmarks
to
find
their
way
back
to
a
desired
spatial
location
(see
Gallistel,
1990).
Some
aspects
of
the
spa-
tial
relations
between
the
goal
and
the
sur-
rounding
landmarks
play
a
role
in
guiding
the
way
back.
Convincing
evidence
that
landmarks
control
behavior
comes
from
studies
in
which
the
array
of
landmarks
supposedly
used
by
the
organism
is
manipulated
before
the
search
for
the
hidden
goal.
Removal
of
the
landmarks
should
cause
disruption
of
the
search,
and
dis-
placements
should
lead
to
systematic
displace-
ments
in
search
behavior.
These
strategies
have
been
used
to
show
that
landmark-based
search
is
found
in
a
variety
of
animals,
including
ro-
dents
(Cheng,
1986;
Collett,
Cartwright,
&
Smith,
1986;
Etienne,
Teroni,
Hurni,
&
Por-
tenier,
1990;
Suzuki,
Augerinos,
&
Black,
1980),
birds
(Cheng,
1988,
1989,
1990;
Cheng
&
Sherry,
1992;
Spetch
&
Edwards,
1988;
Vander
Wall,
1982),
cephalopods
(Mather,
1991),
and
insects
(Cartwright
&
Collett,
1982,
1983;
Dyer
&
Gould,
1983;
Tinbergen,
1972;
von
Frisch,
1953;
Wehner
&
Raiber,
1979).
This
research
was
supported
by
Natural
Sciences
and
Engineering
Research
Council
of
Canada
research
grants
held
by
each
author.
Alex
Soldat,
Ron
Kelly,
and
Rick
Westwood
provided
assistance
with
the
research.
Corre-
spondence
concerning
this
article
should
be
addressed
to
Marcia
L.
Spetch,
Department
of
Psychology,
University
of
Alberta,
Edmonton,
Alberta
T6G
2E9,
Canada
(E-
mail:
mspetch@psych.ualberta.ca).
Some
recent
research
has
addressed
how
the
pigeon
uses
landmarks
to
find
a
place.
Spetch
and
Edwards
(1988)
displaced
an
array
of
pos-
sible
goal
locations
and
found
that
pigeons
were
sensitive
to
both
the
position
in
the
array
and
the
absolute
position
within
the
room
in
lo-
cating
the
goal.
Cheng
(1988,
1989)
tested
pi-
geons
in
a
search
task
in
a
square
arena
and
concluded
that
the
birds'
behavior
was
influ-
enced
by
both
the
arena
itself
and
landmarks
provided
within
the
arena.
He
further
pro-
posed
that
pigeons
use
a
weighted
average
of
vectors
from
various
landmarks
to
the
goal
in
their
search.
This
vector
sum
model
was
later
rejected
on
the
basis
of
further
evidence
from
tests
in
square
arenas
(Cheng,
1990;
Cheng
&
Sherry,
1992).
It
is
now
supposed
that
pigeons
separately
average
the
direction
and
distance
components
of
vectors
(Cheng,
1994).
Spetch,
Cheng,
and
Mondloch
(1992)
repeated
on
a
touch-screen
device
some
manipulations
Cheng
and
Sherry
(1992)
performed
on
the
floor
of
a
laboratory
room.
In
the
touch-screen
task,
the
search
space
is
the
vertical
surface
of
a
monitor,
on
which
various
graphic
stimuli
are
presented
as
"landmarks."
An
infrared-sen-
sitive
touch
screen
records
where
and
when
the pigeons
peck.
Spetch
et
al.
(1992)
found
that
pigeons
used
both
the
graphic
landmarks
and
the
monitor
itself
in
their
search
task,
and
the
pattern
of
results
was
similar
to
that
found
by
Cheng
and
Sherry
(1992).
187
1995,
63,
187-201
NUMBER
2
(MARCH)
KEN
CHENG
and
MARCIA
L.
SPETCH
The
studies
reviewed
above
indicate
that
pigeons
often
use
multiple
landmarks
in
search.
Functionally,
this
is
advantageous
because
the
information
based
on
each
landmark
is
un-
systematically
inaccurate
to
some
extent.
Av-
eraging
information
from
many
landmarks
can
statistically
reduce
inaccuracies,
much
as
tak-
ing
a
larger
sample
gives
one
a
more
accurate
estimate
of
the
mean.
Similarly,
sources
of
in-
formation
that
are
more
accurate
should
be
given
more
weight.
For
instance,
nearer
land-
marks
should
exert
more
effect
than
farther
ones.
This
has
been
found
for
pigeons
(Cheng,
1989)
and
honeybees
(Cheng,
Collett,
Pickard,
&
Wehner,
1987).
But
pigeons
do
not
always
use
multiple
landmarks.
Spetch
and
Mondloch
(1993)
tested
pigeons
on
a
search
task
on
a
touch-screen
monitor
on
which
the
goal
(lo-
cation
to
be
pecked)
was
found
somewhere
in
the
middle
of
an
array
of
four
landmarks.
The
entire
array
appeared
in
different
locations
on
the
screen
from
trial
to
trial,
so
that
the
screen
itself
was
not
a
valid
cue.
Pigeons
usually
re-
lied
on
a
subset
of
the
cues
for
the
task,
some-
times
primarily
one
landmark,
and
different
pigeons
relied
on
different
landmarks.
Two
convergent
pieces
of
evidence
show
this.
First,
if
the
landmark
relied
on
was
removed,
search
was
poor.
Removal
of
other
landmarks
caused
little
disruption.
Second,
if
the
landmark
relied
on
was
moved,
the
pigeons
shifted
their
search
in
the
direction
of
the
landmark
shift.
Shifting
of
other
landmarks
had
little
effect
on
search
behavior.
Selective
control
by
only
a
subset
of
the
available
cues
was
also
replicated
in
a
touch-
screen
study
using
displays
that
consisted
of
digitized
images
of
an
outdoor
scene
(Spetch
&
Wilkie,
1994).
Distances
from
each
land-
mark
to
the
goal
varied
to
a
greater
extent
than
in
the
Spetch
and
Mondloch
study,
and
all
pigeons
showed
strongest
or
exclusive
control
by
the
nearest
landmark.
In
the
present
study,
we
tested
the
selective
use
of
landmarks
in
the
touch-screen
search
task
in
another
arrangement
based
on
the
re-
search
in
square
arenas
in
laboratory
rooms
(e.g.,
Cheng
&
Sherry,
1992).
A
graphic
frame
(approximately
11
cm
by
11
cm)
provided
an
analogue
of
the
arena.
The
goal
was
near
the
middle
of
one
edge
of
the
square
frame,
and
another
landmark
was
found
near
the
goal.
The
entire
"graphic
arena"
(i.e.,
frame,
land-
mark,
and
goal)
was
moved
from
trial
to
trial
on
the
monitor,
so
that
the
monitor
itself
was
not
a
valid
cue.
The
goal
stayed
in
the
same
place
in
the
graphic
arena
from
trial
to
trial.
After
the
birds
learned
the
task,
we
manipu-
lated
the
cues
to
see
whether
the
pigeons'
be-
havior
depended
more
on
the
frame
or
on
the
landmark.
As
in
the
study
by
Spetch
and
Mondloch
(1993),
two
primary
types
of
ma-
nipulations
were
conducted.
On
removal
tests,
either
the
frame
or the
landmark
was
removed.
On
shift
tests,
either
the
landmark
was
shifted
or
one
edge
of
the
frame
was
shifted.
A
final
test
phase
was
conducted
to
determine
whether
pigeons
whose
behavior
showed
little
control
by
the
frame
might
nevertheless
be
able
to
use
the
frame
to
distinguish
a
correctly
placed
landmark
from
an
identical,
incorrectly
placed
duplicate
landmark.
METHOD
Subjects
The
subjects
were
6
adult
pigeons,
none
of
which
had
previously
served
in
a
touch-screen
search
task
using
graphic
landmarks.
All
had
previously
served
in
experiments
conducted
in
standard
operant
conditioning
chambers.
They
were
housed
in
large
individual
cages.
Two
of
the
pigeons
(at
the
University
of
Alberta)
were
housed
in
a
colony
maintained
on
a
12:12
hr
light/dark
cycle
(lights
on
at
6:00
a.m.).
The
4
others
(at
the
University
of
Toronto)
were
maintained
on
a
14:10
hr
light/dark
cycle
(lights
on
at
6:00
a.m.).
The
birds
were
main-
tained
at
approximately
85%
of
their
free-feed-
ing
weights
by