Neisser: Two perceptual systems

Neisser: Two perceptual systems

At this point, the idea of affordances should seem reasonable. A chair is a
chair because it affords sittability. But what happens when someone sits in
your chair? It would appear that humans have some mechanism for recognizing
specific instances of objects. Recognition definitely involves memory
(“my car is a blue Ford Explorer and I parked it in slot 56 this morning”).
Other tasks, like the kind of sleuthing Sherlock Holmes does, may require
inference and interpretation. (Imagine trying to duplicate Sherlock Holmes
in a computer. It’s quite different than mimicking a hungry baby arctic tern.)
Sowhile affordances certainly are a powerfulway of describing perception
in animals, it is clearly not the only way animals perceive. Neisser postulated
that there are two perceptual systems in the brain (and cites neurophysiological
data):110
1. direct perception. This is the “Gibsonian,” DIRECT PERCEPTION or ecological, track of the brain,
and consists of structures low in the brain which evolved earlier on and
accounts for affordances.
RECOGNITION 2. recognition. This is more recent perceptual track in the brain, which ties in
with the problemsolving and other cognitive activities. This part accounts

for the use of internal models to distinguish “your coffee cup” from “my
coffee cup.” This is where top-down, model-based perception occurs.
On a more practical note, Neisser’s dichotomy suggests that the first decision
in designing a behavior is to determine whether a behavior can be
accomplished with an affordance or requires recognition. If it can be accomplished
with an affordance, then there may be a simple and straightforward
way to program it in a robot; otherwise, we will most certainly have to employ
a more sophisticated (and slower) perceptual algorithm.