IT and PCT -- More bad news for IT

CSGnet Archive CSG1994
1

[From Rick Marken (940204.0930)]

In my post to Bill Leach yesterday (940203.1000) I described the
"Marken effect" as evidence for a transport lag in human control
systems. I just realized this morning that the existence of this
effect is really bad news for those who believe that there is
information about the disturbance in perception. In the "Marken
effect" the disturbance waveform (over time) is EXACTLY THE SAME
on two different trials; the exact same series of numbers are added
to the cursor on two different occasions. But the perceptual signal is
different on these two occasions, as is the output variable. If
there is information about the disturbance in perception then the
information that the subject is getting is different on each trial. This
difference is not the result of "noise" because the difference ALWAYS
exists and it always goes in the same direction; the subject seems to get
more information about the disturbance when it is generated by a simulated
control system (because the subject's outputs more accurately counter the
disturbance in this case) than when the disturbance is simply replayed
from a stored table. Why would there be a different amount of information
in one case compared to the other? Everything about the environment
(the disturbance waveform) and the subject is the same in both cases;
all that is different is that the disturbance waveform is generated live in
one case and replayed in the other. But there is absolutely no way the
subject can tell whether the disturbance is being generated live or not;
the subject cannot perceive the cause of the disturbance. Nevertheless,
given the exact same disturbance, the subject always generates more accurate
outputs (closer to being equal to -d) when the d values are generated
in real time rather than being recalled from a table.

How would IT explain the existence of the "Marken effect"?

Best

Rick

2

<Bill Leach 06 Feb 1994 10:35:18

Rick Marken (940204.0930)

Rick; I'm really having trouble with this one! If there indeed ARE the
exact same signals "disturbing" the cursor then there should be NO
perceptual difference.

Have you run this test something like this for verification?:

Run the simulation without a test subject to collect "disturbance data".

Run experiment with subject using disturbance data from a table first and
then repeat using "real-time" generated disturbance data. Compare
results to experiments using reverse order.

The two cases are not the same (that is real time followed by table data)
in that if nothing else were different both the time when each test was
run and the amount of previous "experience" of the subject is different.

At the moment, I personally discount the idea that the time of occurance
for each of the "runs" being different has any significant bearing on
your results [but reserve any sort of "final" judgement :slight_smile: ].

The order of performance of the two runs is something that I would think
IS significant so I am very interested to know if you have been able to
test that idea.

Additionally, I still think that there is a possibility that the two runs
actually ARE different. After all, it actually is a different set of
instuctions that the computer itself is executing to generate the two
scenerios.

-bill