<s>
The	O
octave	B-Application
illusion	I-Application
is	O
an	O
auditory	B-Application
illusion	I-Application
discovered	O
by	O
Diana	O
Deutsch	O
in	O
1973	O
.	O
</s>
<s>
It	O
is	O
produced	O
when	O
two	O
tones	O
that	O
are	O
an	O
octave	B-Language
apart	O
are	O
repeatedly	O
played	O
in	O
alternation	O
(	O
"	O
high-low-high-low	O
"	O
)	O
through	O
stereo	O
headphones	O
.	O
</s>
<s>
Most	O
subjects	O
heard	O
a	O
single	O
tone	O
that	O
alternated	O
in	O
pitch	O
by	O
an	O
octave	B-Language
as	O
it	O
alternated	O
between	O
ears	O
.	O
</s>
<s>
58%	O
of	O
right-handed	O
subjects	O
and	O
52%	O
of	O
left-handed	O
subjects	O
heard	O
a	O
single	O
pitch	O
that	O
switched	O
between	O
octaves	B-Language
as	O
it	O
switched	O
between	O
ears	O
.	O
</s>
<s>
Deutsch	O
proposed	O
that	O
when	O
a	O
single	O
tone	O
that	O
alternates	O
between	O
octaves	B-Language
is	O
heard	O
,	O
this	O
illusion	O
results	O
from	O
the	O
combined	O
operation	O
of	O
two	O
decision	O
mechanisms	O
.	O
</s>
<s>
In	O
a	O
further	O
experiment	O
,	O
Deutsch	O
examined	O
the	O
effect	O
of	O
handedness	O
and	O
familial	O
handedness	O
background	O
on	O
perception	O
of	O
the	O
octave	B-Application
illusion	I-Application
.	O
</s>
<s>
The	O
amplitude	B-Application
of	O
the	O
unheard	O
pitch	O
was	O
then	O
manipulated	O
in	O
order	O
to	O
determine	O
how	O
large	O
it	O
needed	O
to	O
be	O
,	O
in	O
order	O
to	O
counteract	O
the	O
effect	O
,	O
and	O
it	O
was	O
found	O
that	O
a	O
significant	O
amplitude	B-Application
disparity	O
was	O
sometimes	O
needed	O
.	O
</s>
<s>
In	O
yet	O
other	O
experiments	O
,	O
Deutsch	O
varied	O
the	O
relative	O
amplitudes	B-Application
of	O
the	O
high	O
and	O
low	O
tones	O
and	O
asked	O
subjects	O
whether	O
the	O
pattern	O
was	O
of	O
the	O
"	O
right-left-right-left-	O
"	O
type	O
or	O
the	O
"	O
left-right-left-right	O
"	O
type	O
.	O
</s>
<s>
Again	O
,	O
it	O
was	O
found	O
that	O
a	O
large	O
amplitude	B-Application
disparity	O
was	O
sometimes	O
needed	O
to	O
counteract	O
the	O
effect	O
.	O
</s>
<s>
Brancucci	O
,	O
Padulo	O
,	O
and	O
Tommasi	O
argue	O
that	O
the	O
octave	B-Application
illusion	I-Application
should	O
be	O
renamed	O
the	O
"	O
Deutsch	O
illusion	O
"	O
,	O
since	O
,	O
according	O
to	O
their	O
findings	O
,	O
the	O
illusion	O
is	O
not	O
limited	O
to	O
the	O
octave	B-Language
.	O
</s>
<s>
The	O
authors	O
also	O
argued	O
that	O
experiments	O
conducted	O
by	O
others	O
did	O
not	O
clarify	O
whether	O
the	O
high	O
tone	O
and	O
low	O
tones	O
were	O
perceived	O
as	O
being	O
an	O
octave	B-Language
apart	O
.	O
</s>
<s>
Deutsch	O
(	O
2004a	O
)	O
used	O
a	O
new	O
procedure	O
,	O
which	O
provided	O
more	O
explicit	O
documentation	O
of	O
the	O
octave	B-Application
illusion	I-Application
;	O
here	O
musically	O
trained	O
subjects	O
notated	O
precisely	O
what	O
they	O
heard	O
.	O
</s>
<s>
The	O
experiment	O
confirmed	O
that	O
subjects	O
,	O
on	O
listening	O
to	O
the	O
illusion	O
,	O
perceive	O
an	O
octave	B-Language
difference	O
between	O
the	O
ears	O
.	O
</s>
<s>
In	O
addition	O
,	O
the	O
octave	B-Application
illusion	I-Application
,	O
in	O
which	O
an	O
octave	B-Language
difference	O
between	O
the	O
ears	O
is	O
perceived	O
,	O
has	O
been	O
replicated	O
in	O
several	O
other	O
laboratories	O
.	O
</s>
