Transition Perception, Owleye's Introduction

[From Rick Marken (971023.0820)]

The following article seems to be an excellent example of
conventional research that is relevant to the hierarchical control

Lakatos and Shepard, Constraints Common to Apparent Motion in Visual,
Tactile, and Auditory Space, Journal of Experimental Psychology:
Human Perception and Performance, 1997, Vol. 23, No. 4, 1050-1060

The basic finding is that the perception of apparent motion (what
we would call a transition perception) has the same time constraits
across sensory modalities; that is, you see, feel or hear "movement"
of visual, tactile or auditory sensory elements only if these
elements are separated by a certain time interval (stimulus-onset
asynchrony or SOA) which is _the same_ for all modalities.

I came to the same conclusion (in my "Hierarchical behavior of
perception" paper, which is available in at my web site -- see
address below) based on a survey of psychophysical studies of thresholds
for seeing and hearing transitions and sequences. I
guessed that the tactile threshold for _sequence_ perception (for
example) was the same as that for vision and hearing based on
studies of the human ability to _produce_ tactile sequences!

Studies of tactile sequence production (where people generate
finger tap sequences) show that people cannot produce these
sequences much faster than the rate at which they can see and
hear sequences. PCT says that people are controlling their
perception of a tactile sequence when they are "generating"
finger tap sequences. Hence, my guess that the limitation on
the speed with which these sequences could be _produced_ was
actually a limitation on the speed at which these sequences could
be _perceived_.

According to HPCT, all sequences are perceived in the same way --
so they should all have the same "constraints". So the limitation
on the ability to perceive a tactile sequence should be the same
as the limitaiton on the ability to perceive _any_ sequence -- auditory,
visual or tactile. I never tested this directly (by
measuring people's ability to percive _tactile_ sequences). If I
had, I would have expected to find that the temporal threshold
for perception of a tactile sequence (a sequence of taps applied
to the finger tips, for example) would be the same as that for
an auditory or visual sequence.

Lakatos and Shepard did the study I should have done -- though
they did it with transitions rather than sequences. But the
results are exactly what HPCT predicts, viz., the same threshold
for perception of a particular class of perceptual variable (a
transition in this case), regardless of the nature of the lower
level perceptions (visual, auditory or tactile sensations in this
case) of which they are composed.

Jim Dix (971022) --

Greetings. My name is Jim Dix, of Nasa Ames Research Center,
Pilot-in-the-loop Flight Simulation (aircraft modeled as a control

Hi Jim. Say "hi" to Al Ahumada for me. But don't believe a thing
he says about me. I'm much better now;-)

Bill Powers (971023.0700 MDT) suggested that:

it would be helpful for you to download some of our demo programs.
Unfortunately, right now the U. of Illinois server where these
things reside has changed its FTP procedures and the link doesn't
work; we're trying to get that straightened out. Somebody on the
net can probably send you a copy of some of the programs if
you're interested.

This is an excellent suggestion, but for some reason Bill failed
to mention that there are demos available at my website. The URL

These demos seem to work best when run in Netscape 3.0 on are
reasonably fast platform (I get nice performance from a 120MHz
Power Mac, a 166MHz PC and from almost any Unix platform). Each
demo also works fine in Netscape 4.0 but for some reason they
interfere with each other; after running one demo the performance
of another is impaired. There seems to be something wrong with
the Java implementation in Netscape 4.0. I hate to say it but
the demos seem to work fine in the newest version of Explorer
4.0. Anyway, Bill probably failed mention my demos because they
don't run that well on his .001MHz notebook computer;-)

If you do try the demos be sure to read the write ups that accompany
them. These write-ups might help answer some of your questions
about PCT and how the PCT approach to behavior differs from other
approaches, including approaches based on control theory. Bill said
it but I'll just reiterate: the main difference between PCT and all
other approaches to behavior (including approaches based on control
theory) is that PCT is based recognition of the _fact_ that behavior
_is_ a process of control. Behavior is _not_ planned action;
behavior is not action selected by its consequences; behavior is
not a response to inputs. Behavior _is_ the control of perception.
It is necessary to understand -- and convince oneself, by
demontration and test- - of this fact about behavior before trying
to understand the theory of how behavior works: perceptual
control theory.




Richard S. Marken Phone or Fax: 310 474-0313
Life Learning Associates e-mail: