 
What's the problem? 
So, I want to grasp at my pen. Let's see: Some retinal stimulation pattern
is providing me with a rather distorted image of
a pen that is
upside down and changes and flows across
my retina according as I move my eyes, my head, my body position (see
mouse cursor). Not a good starting point for grasping at my pen...
-
So how do I know where my pen is?
The answer in the scope of the information processing approach
would be: This is a complex kind of calculation, taking into account body
position, head position, eye position, retinal information, ...
-
Maybe we should first ask: What does it mean to know where
my pen is?
Would that imply a central representation of the spatial coordinates of
the pen, i.e. something like “The pen is 30 cm in front of, 15 cm to the
right, and 40 cm below...” (and what would be the reference point?), derived
from several sources? And that would in turn be at the basis of my motor
actions? Who would make use of this representation? My homunculus?
Experimental data suggest that spatial knowledge
is distributed, with my left and right arm “knowing” independently
where the pen is, and even different movement trajectories “knowing” independently
where an object is. You want to test this yourself? Try the Do-it-Yourself
experiment.
“Knowing where” means “knowing how to” 
|
Christian
Kaernbach February 2002.