From: mcgrath@cs.uiuc.edu (Robert McGrath)
Subject: Re: Precog not possible?
Reply-To: mcgrath@cs.uiuc.edu
Organization: University of Illinois, Dept of Computer Science
Date: Mon, 21 Dec 1992 18:10:04 GMT

In article <1992Dec21.134228.17022@sol.ctr.columbia.edu>, dave@hyla.hyla.biosci.missouri.edu (Dave Zaloz) writes:
|> Previously Mr. McGrath posted:
|> 
|> ----------------------
|> 	Personally I think precognition is flat
|> out impossible, but I have never said that telepathy or PK are
|> impossible.  They are conceivable, they just aren't in fact true.
|> ---------------------
|> 
|> I certainly respect your opinion Mr. McGrath, but I'm a tad confused.  Is  
|> it that precog is conceivable, but not possible?  As in, I can conceive of  
|> a way to do it, but can't actually do it?  I'm just curious.

From my imperfect understanding of how time works, I simply can't see
how information about the future could be available in the present.  In
fact, I can't really conceive of how this could possibly work, as
'perception' and 'conscious experience' are so closely associated with
'now'.

|> My curiosity stems from my own experiences.  I regularly have those deja  
|> vu experiences were I am in a situation and realize that I had dreamed the  
|> situation beforehand.  It is not as though I had a dream that seemed like  
|> the situation, the dream was exactly the same as the situation.  As an  
|> engineer, I am curious as to how this can be scientifically explained.

I would make a few observations.

First, humans predict the future all the time.  I stand up and walk across
the room, grab the door, and open it.  All these actions are based on
accurate predictions about what will happen as I do these things.
Further, I can predict many mundane things with fair accuracy, fairly
far in the future.  This includes non-trivial things like what my wife
might say in a particular situation, and so on.  These predictions
are essential to human life, and, of course are based on inferences
from past events and hypotheses about the future.  Claims of precognition
must rest on the claim that someone predicted the future in a way
that "could not be done through ordinary means."  Since people are
very adept at predicting the future, this is a very stringent test.
This is also why the classic reports of precognition are always
predictions of inherently unpredictable events, flukes, surprises,
etc.  (There are surely lots of such reports.)

Second, the deja vu experience is definitely real.  Psychologists
who have considered it point out that it consists of the expereince
of the conviction that "this event has happenned before".  This
conviction depends on the current experience being "matched" with
an experience from memory.  This "matching" actually poses a number 
of questions.  

For instance, just how "close" does an experience
have to be to the memory to be "a match"?  We all have repeated
experiences that are similar (e.g., my experience of breakfast is 
pretty much the same every day) so it is certainly possible to
imagine a "false match" of an event that is very similar to, but
actually a close replication of, a previous event.

It is also possible that the "matching" itself goofs up, yielding
a (possibly fleeting) feeling of familiarity when there is actually 
no memory of a previous event.  Other kinds of temporary illusory 
"perceptions" happen all the time, so why not in the perception
of "happened before"-ness?

Combining these two queries, one can also speculate on whether
a partial match between a current event and a remembered event
might, in some cases, result in modification of the recollection,
emphasizing the match and eliminating discordant features.  This
kind of selective editing of memory is well know to happen in
many circumstances, including dream recall.  A dream that partly
predicted an event could be reconstructed as matching the actual
event much more closely than the original dream.  This would
be very difficult to detect, since such dreams are usually not
recorded until after the remarkable match occurs.  (And recollection
of dreams is very unreliable in any case.)

Please note that none of these specualtions involves deliberate
deception or dishonesty on the part of the person who experiences
the deja vu.  These ideas see this experience as a perceptual
illusion, and unconscious goof by ordinary mental processes that
are 99+% reliable.

Please also note that the entire question of what is the difference
between the experience of "now" and the experience of remembering
"then" is open.  The experience can be very similar, yet most of 
the time we are totally certain which is "now" and which is "then".
How does this work?  Note that there is substantial delay between
events in the outside world and subjective awareness of them,
and that current experience is tempered by past experience and
expectations, JUST AS MEMORIES ARE.  Note also that we can mix
awareness of "now" with recollections of the past.  How do we
ordinarily keep these streams of "events" separate?

|> What are the odds that a person could dream an exact instance in his  
|> future?  What are the odds that this can be done at least monthly for the  
|> persons' entire life?  

This is a very difficult probability to estimate!  What are the odds of
ANY particular dream?  How many dreams do we have?  How many do we
remember?  How many dreams do we have that envision events that
DON'T happen at all?  Etc.  I try not to be cautious about estimating
probabilities without very careful consideration.

In light of my comments above, I would caution that the exactness
of the match between dream and later events must be examined carefully
before attempting to estimate the odds of such events.

-- 
  Robert E. McGrath
  Urbana Illinois
  mcgrath@cs.uiuc.edu