[extropy-chat] About ESP, etc.

Damien Broderick thespike at satx.rr.com
Mon Apr 30 22:00:53 UTC 2007

At 02:49 PM 4/30/2007 -0500, I wrote:

>I blame science fiction for this absurd counterfactual of an
>"infallible clairvoyant."

This comment might have had the unfortunate effect of deterring the 
knowledgeable from further comments that might help disambiguate 
cheaters from psychics in such games. Please don't be put off! 
Meanwhile, I posed the same question to several people with long 
experience studying what's dubbed, in our current partial 
understanding of the phenomena, "the paranormal". Here's one 
response; I'd welcome any comments by gts or Ben or others (but 
knee-jerk, semantically empty cries of BULLSHIT might as well stay at home):


Nothing dependent on outside observation of card play can 
disambiguate a psychic from a cheat who's managed to secretly mark 
the cards. This holds for all card games, not just blackjack.

Aside from this, however, patterns of play depend on what wild (or 
mundane) talent a player is exercising.

A card-counter, according to most of the card-counting strategies I 
have seen, plays the optimal strategy at all times; sticks the 
minimum bet most of the time and increases it minimally when the odds 
favor winning. Since the optimal strategy is known it can be observed 
that the player is following it; he profits only because he places 
higher bets during his winning streaks. A psychic, on the other hand, 
may get cues that cause cardplay to deviate from the optimal strategy:

Behavioral clues that a player is a "clairvoyant" who can reliably 
"see through" one thickness of pasteboard:

-Always buys the "insurance" side-bet if the dealer actually does 
have a hidden blackjack, and never buys it otherwise. [Optimal 
strategy never buys insurance -- lacking inside information, it's a 
sucker bet that increases your overall loss rate.]
-Never busts when requesting another card. [This may cause him to 
decline a card when the optimal strategy calls for one.]
-Doubles down whenever his third card brings him to 21, or to a 
number that will beat the dealer's initial hand of 17 or better 
(standard rules require the dealer to stand on such a hand). [This 
will almost certainly produce double-down bets when the optimal 
strategy says otherwise.]
-Keeps initial bet at a constant level. [Inconsistent with card counting.]

Less than 100% reliability will turn these absolutes into tendencies, 
while the ability to see more than the very next card (and dealer's 
face-down card) will allow more impressive stunts during play.

Behavioral clues that a player is a "precognitive" who gets a 
short-term warning only of good or bad outcomes, without details:

-Bets the lower limit most of the time, but unpredictably raises bet 
to the upper limit, and is always dealt a blackjack when this 
happens. [Inconsistent with card-counting. Over the long run, 
probably also inconsistent with dealer's sanity. I am assuming that 
the precog gets immediate feedback on the outcome of one decision or 
event at a time, and winning on a dealt blackjack is the only 
*immediate* good outcome possible when deciding whether to play another hand.]
-Shows same behavior as clairvoyant with regard to "insurance" bets.
-Does not show clairvoyant's immunity to busting. (Sometimes the 
sequence of undealt cards is such that you will bust if take a card, 
and lose if you don't. In these cases the precog's good/bad signal 
gives no guidance since it returns "bad" no matter which option he considers.)
-Does not show clairvoyant's knack for knowing when to double-down 
(that decision requires more than 1 bit of information).
-Will unpredictably stand pat with a poor hand contrary to optimal 
strategy, and wins these hands because dealer busts.

As in the previous example, less than perfect reliability will turn 
these absolutes into tendencies. For plausible levels of psi talent 
(i.e. comparable to levels seen in controlled experiments), extended 
observation would be needed to identify any of these patterns, 
although even a small edge over the house will allow a player to 
profit consistently in the long term.

Of course, whether the ongoing stress and distraction of a game of 
chance is consistent with psi operation *at all* is a completely 
separate and open question.


Damien Broderick

More information about the extropy-chat mailing list