Blackjack is a card game in which players compete against the dealer. The goal is to get a total card value of 21 or close to it without going over, and thereby beat the dealer. Generally, aces count as 1 or 11, face cards as 10, and other cards at their index value. A blackjack consists of an ace and a 10 or face card, and is sometimes referred to as a “natural.” Blackjack is a casino table game, and players place wagers against the house.

The study analyzed the behavior of participants who played a computerized blackjack simulation with rules similar to those used in casinos. Participants placed a wager of up to $100 for each round, and were given five practice rounds before actual play began. Participants were asked to bet according to their own judgment, although they were encouraged to use the hints for better blackjack play that were available to them.

In a separate experiment, we manipulated the amount of information participants had about the optimal strategy for playing blackjack. This manipulation aimed at testing whether confidence in one’s knowledge of blackjack strategy would influence blackjack playing decisions independently of that knowledge. To accomplish this goal, we provided a set of blackjack hints to participants and subsequently measured how frequently and for how long they consulted the hints during gameplay. We also asked questions to measure how much they wanted to learn more about the hints. Behavioral measures included the number of times and the number of seconds spent viewing the hints, which were reverse scored to reflect the fact that higher scores indicated more consultations, and then z-standardized.

The results indicate that unjustified confidence influenced the outcomes of the blackjack games, independent of the participants’ knowledge of basic strategy. Specifically, participants who were more confident in their ability to win at blackjack increased their outcome expectations and reported lower levels of anxiety. Moreover, they were less likely to consult the blackjack hints and showed more risk-taking behaviors. These results highlight the importance of considering the ramifications of unjustified confidence in situations where it is manipulated, such as with gambling and home radon testing.