<s>
The	O
steering	B-General_Concept
law	I-General_Concept
in	O
human	O
–	O
computer	O
interaction	O
and	O
ergonomics	O
is	O
a	O
predictive	O
model	O
of	O
human	O
movement	O
that	O
describes	O
the	O
time	O
required	O
to	O
navigate	O
,	O
or	O
steer	O
,	O
through	O
a	O
2-dimensional	O
tunnel	O
.	O
</s>
<s>
The	O
steering	B-General_Concept
law	I-General_Concept
predicts	O
both	O
the	O
instantaneous	O
speed	O
at	O
which	O
we	O
may	O
navigate	O
the	O
tunnel	O
,	O
and	O
the	O
total	O
time	O
required	O
to	O
navigate	O
the	O
entire	O
tunnel	O
.	O
</s>
<s>
The	O
steering	B-General_Concept
law	I-General_Concept
has	O
been	O
independently	O
discovered	O
and	O
studied	O
three	O
times	O
(	O
Rashevsky	O
,	O
1959	O
;	O
Drury	O
,	O
1971	O
;	O
Accot	O
and	O
Zhai	O
,	O
1997	O
)	O
.	O
</s>
<s>
Within	O
human	O
–	O
computer	O
interaction	O
,	O
the	O
law	O
was	O
rediscovered	O
by	O
Johnny	O
Accot	O
and	O
Shumin	O
Zhai	O
,	O
who	O
mathematically	O
derived	O
it	O
in	O
a	O
novel	O
way	O
from	O
Fitts	B-General_Concept
's	I-General_Concept
law	I-General_Concept
using	O
integral	B-Algorithm
calculus	I-Algorithm
,	O
experimentally	O
verified	O
it	O
for	O
a	O
class	O
of	O
tasks	O
,	O
and	O
developed	O
the	O
most	O
general	O
mathematical	O
statement	O
of	O
it	O
.	O
</s>
<s>
Some	O
researchers	O
within	O
this	O
community	O
have	O
sometimes	O
referred	O
to	O
the	O
law	O
as	O
the	O
Accot	B-General_Concept
–	I-General_Concept
Zhai	I-General_Concept
steering	I-General_Concept
law	I-General_Concept
or	O
Accot	B-General_Concept
's	I-General_Concept
law	I-General_Concept
(	O
Accot	O
is	O
pronounced	O
ah-cot	O
in	O
English	O
and	O
ah-koh	O
in	O
French	O
)	O
.	O
</s>
<s>
In	O
this	O
context	O
,	O
the	O
steering	B-General_Concept
law	I-General_Concept
is	O
a	O
predictive	O
model	O
of	O
human	O
movement	O
,	O
concerning	O
the	O
speed	O
and	O
total	O
time	O
with	O
which	O
a	O
user	O
may	O
steer	O
a	O
pointing	B-Device
device	I-Device
(	O
such	O
as	O
a	O
mouse	B-Device
or	O
stylus	B-Operating_System
)	O
through	O
a	O
2D	O
tunnel	O
presented	O
on	O
a	O
screen	O
(	O
i.e.	O
</s>
<s>
Many	O
researchers	O
in	O
human	O
–	O
computer	O
interaction	O
,	O
including	O
Accot	O
himself	O
,	O
find	O
it	O
surprising	O
or	O
even	O
amazing	O
that	O
the	O
steering	B-General_Concept
law	I-General_Concept
model	O
predicts	O
performance	O
as	O
well	O
as	O
it	O
does	O
,	O
given	O
the	O
almost	O
purely	O
mathematical	O
way	O
in	O
which	O
it	O
was	O
derived	O
.	O
</s>
<s>
Some	O
consider	O
this	O
a	O
testament	O
to	O
the	O
robustness	O
of	O
Fitts	B-General_Concept
's	I-General_Concept
law	I-General_Concept
.	O
</s>
<s>
We	O
see	O
,	O
especially	O
in	O
this	O
simplified	O
form	O
,	O
a	O
speed	O
–	O
accuracy	O
tradeoff	O
,	O
somewhat	O
similar	O
to	O
that	O
in	O
Fitts	B-General_Concept
's	I-General_Concept
law	I-General_Concept
.	O
</s>
<s>
oriented	O
perpendicular	O
to	O
the	O
axis	O
of	O
motion	O
)	O
can	O
be	O
modeled	O
with	O
this	O
form	O
of	O
Fitts	B-General_Concept
's	I-General_Concept
law	I-General_Concept
:	O
</s>
<s>
yielding	O
the	O
general	O
form	O
of	O
the	O
steering	B-General_Concept
law	I-General_Concept
.	O
</s>
<s>
Steering	B-General_Concept
law	I-General_Concept
has	O
been	O
extended	O
to	O
predict	O
movement	O
time	O
for	O
steering	O
in	O
layers	O
of	O
thickness	O
t	O
(	O
Kattinakere	O
et	O
al.	O
,	O
2007	O
)	O
.	O
</s>
