<s>
In	O
the	O
context	O
of	O
human	O
–	O
computer	O
interaction	O
,	O
a	O
modality	B-General_Concept
is	O
the	O
classification	O
of	O
a	O
single	O
independent	O
channel	O
of	O
sensory	O
input/output	B-General_Concept
between	O
a	O
computer	O
and	O
a	O
human	O
.	O
</s>
<s>
A	O
system	O
is	O
designated	O
unimodal	O
if	O
it	O
has	O
only	O
one	O
modality	B-General_Concept
implemented	O
,	O
and	O
multimodal	B-Application
if	O
it	O
has	O
more	O
than	O
one	O
.	O
</s>
<s>
When	O
multiple	O
modalities	B-General_Concept
are	O
available	O
for	O
some	O
tasks	O
or	O
aspects	O
of	O
a	O
task	O
,	O
the	O
system	O
is	O
said	O
to	O
have	O
overlapping	O
modalities	B-General_Concept
.	O
</s>
<s>
If	O
multiple	O
modalities	B-General_Concept
are	O
available	O
for	O
a	O
task	O
,	O
the	O
system	O
is	O
said	O
to	O
have	O
redundant	O
modalities	B-General_Concept
.	O
</s>
<s>
Multiple	O
modalities	B-General_Concept
can	O
be	O
used	O
in	O
combination	O
to	O
provide	O
complementary	O
methods	O
that	O
may	O
be	O
redundant	O
but	O
convey	O
information	O
more	O
effectively	O
.	O
</s>
<s>
Modalities	B-General_Concept
can	O
be	O
generally	O
defined	O
in	O
two	O
forms	O
:	O
human-computer	O
and	O
computer-human	O
modalities	B-General_Concept
.	O
</s>
<s>
Any	O
human	O
sense	O
can	O
be	O
used	O
as	O
a	O
computer	O
to	O
human	O
modality	B-General_Concept
.	O
</s>
<s>
However	O
,	O
the	O
modalities	B-General_Concept
of	O
seeing	O
and	O
hearing	O
are	O
the	O
most	O
commonly	O
employed	O
since	O
they	O
are	O
capable	O
of	O
transmitting	O
information	O
at	O
a	O
higher	O
speed	O
than	O
other	O
modalities	B-General_Concept
,	O
250	O
to	O
300	O
and	O
150	O
to	O
160	O
words	B-Device
per	I-Device
minute	I-Device
,	O
respectively	O
.	O
</s>
<s>
Though	O
not	O
commonly	O
implemented	O
as	O
computer-human	O
modality	B-General_Concept
,	O
tactition	B-Device
can	O
achieve	O
an	O
average	O
of	O
125	O
wpm	B-Device
through	O
the	O
use	O
of	O
a	O
refreshable	O
Braille	O
display	O
.	O
</s>
<s>
Other	O
more	O
common	O
forms	O
of	O
tactition	B-Device
are	O
smartphone	B-Application
and	O
game	O
controller	O
vibrations	O
.	O
</s>
<s>
Computers	O
can	O
be	O
equipped	O
with	O
various	O
types	O
of	O
input	B-Device
devices	I-Device
and	O
sensors	O
to	O
allow	O
them	O
to	O
receive	O
information	O
from	O
humans	O
.	O
</s>
<s>
Common	O
input	B-Device
devices	I-Device
are	O
often	O
interchangeable	O
if	O
they	O
have	O
a	O
standardized	O
method	O
of	O
communication	O
with	O
the	O
computer	O
and	O
afford	O
practical	O
adjustments	O
to	O
the	O
user	O
.	O
</s>
<s>
Certain	O
modalities	B-General_Concept
can	O
provide	O
a	O
richer	O
interaction	O
depending	O
on	O
the	O
context	O
,	O
and	O
having	O
options	O
for	O
implementation	O
allows	O
for	O
more	O
robust	O
systems	O
.	O
</s>
<s>
With	O
the	O
increasing	O
popularity	O
of	O
smartphones	B-Application
,	O
the	O
general	O
public	O
are	O
becoming	O
more	O
comfortable	O
with	O
the	O
more	O
complex	O
modalities	B-General_Concept
.	O
</s>
<s>
Speech	B-Application
recognition	I-Application
was	O
a	O
major	O
selling	O
point	O
of	O
the	O
iPhone	B-Operating_System
4S	I-Operating_System
and	O
following	O
Apple	O
products	O
,	O
with	O
the	O
introduction	O
of	O
Siri	B-Application
.	O
</s>
<s>
Having	O
multiple	O
modalities	B-General_Concept
in	O
a	O
system	O
gives	O
more	O
affordance	O
to	O
users	O
and	O
can	O
contribute	O
to	O
a	O
more	O
robust	O
system	O
.	O
</s>
<s>
Having	O
more	O
also	O
allows	O
for	O
greater	O
accessibility	O
for	O
users	O
who	O
work	O
more	O
effectively	O
with	O
certain	O
modalities	B-General_Concept
.	O
</s>
<s>
Multiple	O
modalities	B-General_Concept
can	O
be	O
used	O
as	O
backup	O
when	O
certain	O
forms	O
of	O
communication	O
are	O
not	O
possible	O
.	O
</s>
<s>
This	O
is	O
especially	O
true	O
in	O
the	O
case	O
of	O
redundant	O
modalities	B-General_Concept
in	O
which	O
two	O
or	O
more	O
modalities	B-General_Concept
are	O
used	O
to	O
communicate	O
the	O
same	O
information	O
.	O
</s>
<s>
Certain	O
combinations	O
of	O
modalities	B-General_Concept
can	O
add	O
to	O
the	O
expression	O
of	O
a	O
computer-human	O
or	O
human-computer	O
interaction	O
because	O
the	O
modalities	B-General_Concept
each	O
may	O
be	O
more	O
effective	O
at	O
expressing	O
one	O
form	O
or	O
aspect	O
of	O
information	O
than	O
others	O
.	O
</s>
<s>
There	O
are	O
six	O
types	O
of	O
cooperation	O
between	O
modalities	B-General_Concept
,	O
and	O
they	O
help	O
define	O
how	O
a	O
combination	O
or	O
fusion	O
of	O
modalities	B-General_Concept
work	O
together	O
to	O
convey	O
information	O
more	O
effectively	O
.	O
</s>
<s>
Complementary-redundant	O
systems	O
are	O
those	O
which	O
have	O
multiple	O
sensors	O
to	O
form	O
one	O
understanding	O
or	O
dataset	O
,	O
and	O
the	O
more	O
effectively	O
the	O
information	O
can	O
be	O
combined	O
without	O
duplicating	O
data	O
,	O
the	O
more	O
effectively	O
the	O
modalities	B-General_Concept
cooperate	O
.	O
</s>
<s>
Having	O
multiple	O
modalities	B-General_Concept
for	O
communication	O
is	O
common	O
,	O
particularly	O
in	O
smartphones	B-Application
,	O
and	O
often	O
their	O
implementations	O
work	O
together	O
towards	O
the	O
same	O
goal	O
,	O
for	O
example	O
gyroscopes	O
and	O
accelerometers	O
working	O
together	O
to	O
track	O
movement	O
.	O
</s>
