Intermittent Positive Reinforcement in Puzzle & Dragons

Intermittent Positive Reinforcement in Puzzle & DragonsI’ll freely admit it; I’m addicted to Puzzle & Dragons, and I’m certainly not the only one. I have clocked up my 211th consecutive day playing what reviewers have described as “portable crack“, and I’m surprised at that. There have been plenty of casual gaming titles that have kept me interested briefly, but nothing has come close to 211 consecutive days of logging on, without fail. When I needed to replace my phone, my PAD game state was the only thing I worried about backing up. How has it managed to keep me interested? By consistently and successfully applying principles of “intermittent positive reinforcement”.

If you somehow have yet to experience Puzzle & Dragons (and I’m confident that if I put a download link here, you wouldn’t return to read the rest of the article), the game is available on all the major mobile platforms. It combines familiar “match 3” gameplay – with a slight twist – plus monster collecting, evolving, and battling that appears in Pokémon and other role-playing titles. That description does not give the idea justice; a combination like that may not sound particularly compelling or even likely to work – but it does, and it does so incredibly well.

What’s Intermittent Positive Reinforcement?

My wife is far better qualified to explain this, but I’ll give it a go. Intermittent positive reinforcement, or more precisely variable ratio reinforcement scheduling, was studied by behavioral psychologist B. F. Skinner, whose experiments (on pigeons) suggested that providing rewards, but not at every occurrence, was most successful at encouraging the desired behavior.

B. F. Skinner - Intermittent Positive ReinforcementSkinner was not without his critics, including some who accused him of using his own children as test subjects. He also held controversial beliefs about concepts such as free will, which he strongly claimed was merely an illusion. Nevertheless, Skinner’s results are widely applicable in many areas, such as the study of gambling addiction. A June 2002 survey named him the most influential psychologist of the 20th century, and, yes, he did indeed “lend” his surname to the school principal in The Simpsons. You may find many of his works online at the B. F. Skinner Foundation.

A good example is house-training a puppy. If you reward the animal for good behavior on every occasion, the puppy merely learns to expect the treat every time, not learn how to behave without the bribe. Punishing the animal for bad behavior is not as effective, because bad experiences have a much stronger effect than good ones. With a schedule of intermittent positive reinforcement, in theory the puppy will behave in the hope of reward, but continue the desired behavior the next time.

What about Puzzle & Dragons?

The theory of intermittent positive reinforcement applies particularly well to games and gambling; slot machines are an obvious example. It is a large part of what makes a game addictive. The impressive thing about Puzzle & Dragons is the theory applies almost universally through every feature of the game. The basic gameplay of matching colors and stringing the matches into combos has random elements that present the potential of great rewards while at the same time not making the player feel at the mercy of the random number generator. The player receives unpredictable gifts for logging in every day. There is always a limited-time special event, tailored to match the days of the week where participation is likely to drop otherwise. Around once per day, the player gets a shot at the “egg machine” – it is no coincidence it works like a slot machine – and just might bag a rare monster or a needed ingredient. The title does use “wait gaming“, allowing a limited amount of play before the user must either wait or spend for a recharge, but it is not obnoxious or greedy. An overnight charge is enough for plenty of entertainment; there is always a free level (without rewards) to pass the time. Growing your monsters randomly gives added bonuses. Paying players are not necessarily guaranteed the best monsters but have to try their luck on the egg machine; thus the free players do not feel alienated – they even have a daily chance to borrow the strong monsters from buddies.

Those are just a few examples; there are many more features in Puzzle & Dragons with a similar design philosophy. Features like this do not come about by accident; game mechanics are exceptionally difficult to get right. Too hard, and players get discouraged; too easy, and players get bored – and an easy feature cannot be patched up after the fact without the player base complaining about a “nerf“. You can be certain the servers at GungHo are collecting deep analytics that the developers use to aim for the perfect balance. It testifies to their skill that, even knowing why the game is addictive – intermittent positive reinforcement and all – I’m still hooked. There are other titles out there that fail, and make me feel like one of Skinner’s pigeons.

Puzzle & Dragons logo image from j bizzie (CC BY 2.0)
B. F. Skinner at Harvard circa 1950 image from Silly Rabbit at Wikimedia Commons (CC BY 3.0)

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