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Journal
of
Experimental
Psychology:
Animal
Behavior
Processes
1984,
Vol.
10, No. 2,
138-148
Copyright
1984
by the
American
Psychological
Association,
Inc.
Music
Discriminations
by
Pigeons
Debra
Porter
and
Allen
Neuringer
Reed
College
Pigeons learned
to
discriminate between complex musical
sequences.
Two
birds
responded
at
more
than
80%
correct
in a
single-operandum
discrimination
learning
task when
the S+ was a
1-min
excerpt
of
Bach
flute
music
and the S- was a
1-
min
excerpt
of
Hindemith viola music (Experiment
1).
Four pigeons responded
at
more than
70%
correct
when they were required
to
peck
the
left
of two
disks during
presentations
of any
portion
of a
20-min
Bach organ piece
and to
peck
the
right
disk during
any
portion
of
Stravinsky's
Rite
of
Spring
for
orchestra
(Experiment
2).
These discriminations were learned slowly. However,
the
birds
generalized
con-
sistently
and
independently
of the
instruments
involved when
presented
with novel
musical excerpts (Experiment
3).
They preferred
the
left
"Bach
disk"
when
,novel
excerpts
from
Buxtehude
and
Scarlatti were introduced
and the
right "Stravinsky
disk"
when novel excerpts
from
Eliot
Carter, Walter
Piston,
and
another
Stravinsky
work
were introduced. People responded similarly. Therefore
the
pigeon's response
to
complex auditory events
may be
more like
the
human's
than
is
often
assumed.
Studies
of
stimulus control
of
animal
be-
havior
have
been extended
from
"simple"
physical dimensions, such
as
intensity, wave-
length,
frequency,
or
angle (Blough
&
Blough,
1977;
Mackintosh, 1974),
to
more complex
stimuli
that,
although varying
in
sometimes
poorly
understood
ways
along multiple
di^
mensions,
can be
related
to
human concept
formation (e.g., Mervis
&
Rosph, 1981).
Herrnstein
and his
colleagues haye shown that
pigeons
discriminate complex
and
abstract
vi-
sual
concepts. When required
to
peck
a re-
sponse
disk when
a
picture containing
a
person
is
projected
on a
small screen,
the
birds learned
the
concept
of
"person"
and
responded cor-
rectly
to
pictures
they
had
never before seen
(Herrnstein
&
Loveland,
1964). Additional
work
showed that birds learned
the
complex
concepts
of
angularity, trees, leaves,
fish, and
water
(Cerella, 1979; Herrnstein, 1979;
Herrnstein
& de
Villiers,
1980; Herrnstein,
Loveland,
&
Cable,
1976;Lubow,
1974;Malott
&
Siddall, 1972). Such demonstrations
are
important,
for
they show
the
extent
to
which
animals
and
people perceive
and
behave
sim-
This
article
is
based
on a
thesis presented
by the first
author
to
Reed
College
in
partial
fulfillment
of the re-
quirements
for a BA
degree.
Requests
for
reprints
should
be
sent
to
Allen
Neuringer,
Department
of
Psychology,
Reed
College,
Portland,
Oregon
97202.
ilarly.
Humanlike animal discriminations
have
also
been
shown
when auditory stimuli
are
used.
Hulse,
Cynx,
&
Humpal
(1984)
showed
that starlings could discriminate between
sound
rhythms
and
pitches
and
that they gen-
eralized like human subjects. D'Amato
and
Salmon
(1982)
showed
that both monkeys
and
rats
we,re
able
to
discriminate between simple
auditory
"tunes."
The S+
stimulus
was a se-
quence
of six
frequencies,
the first
four
rising,
the fifth
falling,
and the
last again rising, with
the
complete stimulus taking
1.8 s. The
S—
stimulus
was a 2-s
period
of 17
monotonically
descending
and 16
monotonically ascending
frequencies.
The
present study extends
the
D'Amato
and
Salmon
research
to a
more complex auditory
domain
and to
possibly
a
more
unlikely
sub-
ject. There
were
two
main questions: First,
can
pigeons discriminate between
two
specific
episodes
of
classical music? Second,
if
yes,
can
they
also respond
differentially
to
broad cat-
egories
of
musical stimuli,
as do
people?
The
pigeon
provides
a
relatively strong test
of
whether
animals
can
learn
to
adequately dis-
criminate complex auditory patterns.
For al-
though
pigeons
are
known
to
discriminate
be-
tween
pigeon calls (Beer,
1970)
and
aspects
of
their
audiograms
are
similar
to
human
au-
diograms
(Harrison
&
Furumoto,
1970;
Heise,
1953),
a
number
of
researchers
have
concluded
that pigeons
are
relatively poor
at
utilizing
au-
138
MUSIC
DISCRIMINATIONS
BY
PIGEONS
139
ditory
cues (e.g., Mackintosh, 1974;
Shettle-
worth,
1972).
Experiment
1
The first
experiment asked
whether
pigeons
could discriminate between excerpts
from
two
pieces
of
classical
music,
one by
Bach
and the
other
by
Hindemith.
Method
Subjects
Two
White
Carneaux
pigeons (No.
25 and No. 70)
were
maintained
at 80% of
their normal body
weights.
They
had
continuous access
to
grit
and
water
in
their
home
cages
but
received grain
only
once
per day
after
the ex-
perimental sessions, Both birds
had
previous experience
in
a
variety
of
operant
conditioning experiments
but had
not
been exposed
to
auditory conditioning tasks.
Apparatus
A
Lehigh
Valley
pigeon chamber,
30 X 35 X 40 em,
contained
a
front
panel with
a
yellow
transilluminated
response disk located
9 cm
above
and 5 cm to the
left
of
a
reinforcement dispenser that occasionally provided
3 s
of
access
to
mixed grain.
A
small speaker
was
mounted
behind
the
front
panel,
and
musical stimuli
were
presented
with
a
Craig
Model
2603
or
Sony Model
TC-105
tape
recorder.
The
stimuli
consisted
of a
1-min
excerpt
from
J. S.
Bach's
Prelwle
in
C
Minor
for
flute, which
was
con-
tinually
repeated
to
comprise
the S+, and a
1-min excerpt
from
P.
Hindemith's
Sonata,
Op. 25, No. 1 for
viola,
which
was
repeated
to
comprise
S—.
The two
stimuli
were
selected
because
they are: appreciably
different
to
adult human
listeners.
Relay
equipment
in a
separate room controlled
all
aspects
of the
experiment. Although intensities were
not
measured,
the
musical stimuli were characterized
as
"loud"
by
human listeners.
Procedure
Phase
1. The
Bach
and
Hindemith pieces alternated
on
the
average
of
once
per
min, with
a 5-s to
3-min range
of
intervals. When Bach played,
S+
contingencies
were
in
effect,
and
every
15th
peck
to the
disk produced rein-
forcement
(FR
15). When
Hindemith
played,
the S-
con-
tingencies
were
in
effect
and
food
was
unavailable.
To
assure that responses
in S-
were
not
accidentally
rein-
forced,
the
stimuli
did not
switch
from
S- to S+
until
at
least
10 s had
elapsed without
a
response. Each
of 33
sessions terminated
after
50
reinforcements
had
been
pre-
sented.
Phase
2. To
assure that
the
behaviors
were
not
being
controlled exclusively
by fixed-ratio
schedule
cues—that
is,
if the
15th
peck
were
reinforced, that
would
be a cue
for
S+
contingencies,
and if the
15th
peck were
not
rein-
forced,
S- was in
effect—the
contingency
in S+ was
changed
to a
variable-interval
(VI)
schedule under which
pecks
were
reinforced
variably
in
time.
For a
few
sessions.
reinforcers
were
scheduled
to
average
6/min,
approximately
the
same
frequency
as
under
the fixed-ratio
schedule; then
reinforcement
frequency
was
decreased
to
2/min
for
35
Phase
3. Two
control sessions
were
inserted during
the
VI
phase
to
test whether
the
birds
were
discriminating
between
attributes
of the
musical stimuli
or
whether
ar-
tifacts
were
responsible
for the
behaviors. During
the first
session,
the
tape recorders were disconnected
from
the
speaker
while
all
other contingencies
were
the
same
as in
Phase
2.
During
the
second session, blank tapes replaced
the
music—the
recorders remained
on but
transmitted
no
music—and
all
other contingencies were
the
same
as in
Phase
2.
Results
and
Discussion
Both
birds learned
the
Bach-Hindemith
discrimination,
as
shown
in
Figure
1,
and
over
the
last
five
sessions
of the first
phase
(FR
reinforcement),
they responded correctly
77%
and 89% of the
time. (This percentage equals
the
response rates
in
S+
divided
by the sum
of
the
response rates
in S+ and
S-.)
When
the
reinforcement schedule
was
changed
to VI,
performances were temporarily
disrupted,
but the
birds again came
to
respond
more
frequently
to
Bach than
to
Hindemith,
and
over
the
last
five
sessions
of
this phase
they
responded
correctly
86% and 82% of the
time (Figure
1).
Either disconnecting
the
tape recorders
or
substituting blank tapes caused
the
percentage
of
correct responses
to
fall
immediately (see
points marked
"a" and
"b"
in
Figure
1), al-
though
in
both cases,
and for
both
birds,
the
percentages were above 50%.
The
schedule
contingencies
or
some artifact
in the
sound-
presenting apparatus
may
have provided par-
tial
cues. However,
the
large
difference
in the
percentage
of
correct responses between these
control sessions
and
the-music
sessions
indi-
cates
that
the
discriminations were largely
based
on the
music.
Experiment
2
The
second experiment attempted
to
con-
firm and
extend
the
above
findings.
First, much
longer
musical compositions served
as
dis-
criminative stimuli
to
help rule
out the
pos-
sibility that
the
pigeons were responding
to a
single,
simple
differentiating
attribute
of the
two
discriminative cues.
For
example,
if
only
one of the
stimuli
in
Experiment
1
happened
to
have
a
note
of a
given
frequency
or
intensity,
140
DEBRA
PORTER
AND
ALLEN
NEURINGER
that
note
and
that
alone might have guided
the
discriminations.
In the
present
experiment,
the
length
of the
excerpts
comprising
S+ and
S-
stimuli
was
increased
from
1-min
to
more
than
20-min.
Since
a
trial
consisted
of an av-
erage
of 1
min,
the
exact nature
of the
stimulus
varied greatly
from
trial
to
trial.
Second,
to
extend
the
generality
of the findings,
pigeons
of
three
different
breeds
were
used.
Third,
again
to
extend
the
generality (and
to
provide
for
the
generalization testing
to
follow),
a
choice-assessment method
was
used
rather
than
the
single-operandum
method
in
Exper-
iment
1.
Method
Subjects
Two
White
Carneaux
(No.
96 and No.
18),
a
Schietti
Modena
(No. 67),
and two
Silver King (No.
16
and No.
62)
pigeons were maintained
at 85% of
their
free-feeding