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Best of Alan Krigman

Gaming Guru

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Does Peek-A-Boo Blackjack Affect Decision Strategy?

14 April 1997

In olden days, blackjack dealers always peeked at their hole cards when they had ace- or 10-up. With ace-up, it was after closing insurance. If they had blackjack, they exposed it, ending the round without further dealing.

Verifying the hole card was good for the casino; more hands could be dealt per hour. Players liked the procedure too; it avoided the frustration of drawing into a good hand when the situation was hopeless anyway.

Checking for blackjack fell into disfavor. One reason was that unscrupulous dealers could signal cohorts at the table as to the hole card when there was no blackjack. And honest dealers sometimes reacted unconsciously to what they saw, responding with a "tell." Either way, stalwart students of the game gained unintended edge. For instance, a dealer might purposely or inadvertently smile upon seeing a five or six under a 10, so perceptive players would stand on 12 through 16. Alternately, a dealer might tap the table upon seeing a second 10, so bright bettors would hit 17 through 19, knowing they'd surely lose otherwise.

Ingenuity and technology are bringing back the practice of checking for blackjack. Minus the opportunity for cheating or reading tells. Peek-a-boos, now appearing on gaming tables everywhere, show the dealer whether there's a blackjack but - if not - don't reveal the actual value of the hole card.

This raises the question whether players should alter their decision strategies against aces or 10s which can't become blackjacks. The answer is "no." Basic strategy, the set of decisions which minimize house advantage, is the same against ace- or 10-up whether or not the dealer may have blackjack.

Here are two examples. Basic strategy says to split pairs of aces or eights against an ace-up. Many solid citizens attribute this rule, in part, to the fact that only the original bet is lost if the dealer has a blackjack; additional bets made by splitting or doubling are out of action and returned to the player. So, absent the possibility of a "natural," are these splits still correct?

Proper play for these hands can be seen by comparing "expectations" for alternative decisions in each case. I'll give expectation, net win or loss assuming a statistically-correct distribution of results, for a hundred $10 hands played various ways. Figures are in dollars, and assume a six-deck shoe with no resplitting; slightly different values, but bearing the same relationships, would be obtained in games with other rules.


Expected Net Win or Loss in Dollars
after a Hundred $10 Hands
with Pairs of Aces and Eights Played Various Ways
against a Dealer's Ace-up

 
A-A
8-8
hit
-022
-514
stand
-666
-663
surrender
-500
-500
double
-620
-813
split
+127
-385

 

The table shows that by splitting aces against an ace-up with no possibility of a dealer blackjack, a player expects a net profit of $127 after the hundred $10 hands. This contrasts with losses from $22 to $666 for the other decisions. Likewise, by splitting eights against an ace-up with no possibility of a dealer blackjack, a player expects a net loss of $385. Bad. But less so than the losses from $500 to $813 for the other options.

Sure, you might split aces and pull dogs as second cards. Or maybe you split eights, are rewarded with threes on both sides so you double, then get garbage. Ordinarily, you'd hope the dealer has blackjack so you'll lose only one rather than multiple bets. In a peek-a-boo game, you can't get off this easily.

Still, the laws of probability as codified in basic strategy - not hunches or qualitative "what-if's" - dictate the best front-end choice. Sumner A Ingmark elegantly epitomized the aptness of acting astutely in such uncertain situations when he wrote:

Decisions weak in cases dubious,
Change bottom lines from black to rubious.

Alan Krigman

Alan Krigman was a weekly syndicated newspaper gaming columnist and Editor & Publisher of Winning Ways, a monthly newsletter for casino aficionados. His columns focused on gambling probability and statistics. He passed away in October, 2013.
Alan Krigman
Alan Krigman was a weekly syndicated newspaper gaming columnist and Editor & Publisher of Winning Ways, a monthly newsletter for casino aficionados. His columns focused on gambling probability and statistics. He passed away in October, 2013.