Slots that include a gamble feature typically offer players the chance to double their winnings that have just been accrued on the board or in a bonus game. They generally consist of a 50/50 choice where winnings are doubled if you win. If you make the wrong prediction all winnings are lost. The classic feature utilises playing cards and invites players to guess whether the next card drawn from the pack will be red or black.

Some features allow you to keep gambling if you make the right prediction, and winnings can quickly be doubled up several times to make huge amounts. However, with every guess there is a chance of losing everything. Players are given the option to collect winnings or to go again in the hope of doubling their money.

Online slot makers have incorporated a number of different 50/50 options into their games. Some developers, such as Microgaming even allow you to control the payout odds. More on that later, but for now, here are some of the most popular types of gamble features in use today.

Gamble features involving cards are the most common among online slots. These usually require you to predict whether the next card will be red or black. Many?video poker games offer a hi-lo mini-game where players are asked to decide whether the next card will be higher or lower than the one shown. I would like to see the actual payout percentages on these as I find it hard to believe the game is using a true RNG. If you have ever played Jacks Or Better and played hi-lo after a win, you will know the feeling of hitting a deuce when you choose higher than the "3" that is showing.

Gamble options are triggered after a win and most only give the option to make a double or nothing wager. There are a few games out there that allow you to bank some of your winnings before betting the rest, but they are among the minority.

Another classic type of gamble feature is the good old coin toss, which requires you to predict the outcome of a coinflip. Simply choose heads or tails to double your winnings. One of my favourite games -?Betsoft’s At the Copa 3D slot gives players this option after a win.

Dice roll features work in the same way, requiring you to make a 50/50 choice on whether the dice will land on an odd or even number. Guess correctly and you will double your winnings, but get it wrong and you will lose the lot. You may occasionally come across the option to choose an exact number which will of course increase the payout odds, but will have greater variance.

Some developers have taken things even further and added a level of interactivity. Many of the?latest Microgaming slot machines feature a variable gamble bonus, whereby you can control how much you stand to win if you choose to gamble.

On several games this unique feature takes the form of a globe, with a red losing section and a green winning section. Before making your wager, you are able to increase or decrease the size of both areas, with your potential winnings going up and down accordingly. When you have set up the globe, a compass needle spins around it, and you win or lose depending which section it stops in.

The low risk option involves making the winning area as large as possible and the losing area as small as possible. If you win, you will only be awarded 1/20th of the size of your wager. The high risk option would be to make the losing area as large as possible and the winning area as small as possible. Obviously this will make it much harder to hit the winning section, but will have a much higher payout - 20 times the wagered amount.

Gamble features are so popular with players because they add real excitement to the game. They provide the chance to double your winnings but also come with the risk of losing everything. That really gets the pulse racing, which is why so many punters find them hard to resist.

We’ve got a host of?free online slots where you can test these out for yourselves. Good luck!