Your win lies in the 'eyes' of opponent

It turns out, winning in Blackjack is as easy as watching the opponents' eyes, according to a recent study.

Blackjack players who hold high-value cards tend to glance fleetingly to the right, whereas those with a lower-value hand do so spontaneously to the left. This is according to the research on aspects of mental arithmetic, led by Kevin Holmes of Colorado College in the US.

Research suggests that you can actually judge something about the mental arithmetic that people are doing silently in their heads based on involuntary tell-tale signs they produce. For example, when pointing to an arithmetic solution on a visually presented number line, participants are biased leftward on subtraction problems and rightward on addition problems.

Holmes and his colleagues, Vladislav Ayzenberg and Stella Lourenco of Emory University, conducted two experiments to find out what role attention plays in such a mental number line within a real-life setting.

It was found that participants' spontaneous eye movements along the horizontal axis reflected the overall numerical value of their cards. Participants tended to look toward the left side of the screen when they had smaller-value hands, while they looked toward the right side when they had larger-value hands.

These effects were driven by the total value of the cards that a player had in the hand. It was not influenced merely by the number of cards that a player was holding, nor the value of the card that he or she was just dealt.

"Whether our findings will help blackjack players in real life still has to be investigated," said Holmes. "The relatively small differences in absolute gaze position we found here may be undetectable to the naïve observer. Perhaps following training, observers could rely on gaze patterns to infer hand value."

The study appears in Psychonomic Bulletin & Review.