Principles of PCT-Guided Research
1. Behavior serves one function and one function only:
to control perceptual signals.
2. Perceptual signals are neural currents. For each
perceptual signal there is a single neural current
that embodies it. The system making use of a
particular neural current does not "know" what
perception the neural current represents.
3. A control system acts so as to keep its perceptual
signal close to its reference level. It does this
(a) comparing the perceptual signal to the
(b) generating an output signal whose effect
tends to reduce the error between
perception and reference.
This effect is called negative feedback. Because
error between the perceptual signal and the
reference signal generates output which in turn
affects the perceptual signal and thus the error,
a control system is a closed loop system.
4. Control systems are organized hierarchically, with the
outputs of higher-level systems serving as reference
levels (or other parameters such as gain values) for
lower-level systems. The higher-level systems control
their perceptual signals through the activities of the
lower-level systems, which serve to close the loop so
as to produce negative feedback in the higher-level
The goals of PCT research are:
a. to discover what perceptual signals are under control
in a given specific task;
b. to determine the parameters of the control systems
involved in specific tasks. These include input
functions, comparator functions, reference values
(or sources), and output functions;
c. to discover how control systems are organized in
the nervous systems of real organisms;
d. to discover how control systems come into being
and how their parameters change as a result of
e. ultimately, to provide a single model of CNS
organization that is consistent with biology
and accounts for the organism's behavior in
all situations, including those involving the
failure-modes of the system.
1. Appropriate research methods are those that focus
on the individual. Thus PCT-guided research is
"single subject" research.
2. Reliability of findings is established through
3. The behavior of closed loop systems cannot be
correctly analyzed using methods which assume
4. The first step in understanding behavior is to
identify the perceptual signal(s) that the
behavior controls. Doing so requires applying
"THE TEST," which involves applying disturbances
to the putative perceptual signal(s) and observing
whether (and how well) the disturbances are resisted.
5. The second step is to construct a computer model of
the system which incorporates hypothesized control
systems and their interconnections. The model
should be consistent with the known biology of
the organism whose behavior is being modeled.
6. The third step is to compare the computer model's
behavior to that of an actual individual organism
and to adjust the model's parameters so that the
model's behavior closely matches the organism's.
If no adjustment of parameters achieves this result,
the model must be modified and tested again against
real behavior. The "correct" model will yield an
excellent fit to the original data and, after
suitable parameter adjustment, should yield an
excellent fit to data from other individuals tested
in the same situation.