Video games change as technology improves and designers have new ideas but do you know the one thing that remains constant? The player.

Understanding the player forever improves your ability to make games, no matter the changes in tech. To understand the player better let's look to behavioral psychology; the study of how organisms react to stimulus. Behavioral psychology research is directly applicable to games and actively used. Have you ever heard anyone talking about a skinner box? Well that's a part of behavioral psychology. Learn a little about behaviors and reactions, and you'll be a better game designer.


Bhurrhus Fredrick Skinner constructed a clever type of experiment that had a massive impact on the behavioral psychology field. Most of Skinner's experiments are about a box. The world is a noisy place, say you're living in the jungle, your senses are bombarded with inputs! It's overwhelming and as a scientist it's very hard to understand exactly what you're responding to when you perform some action. If you're placed inside a plain box, the noisy environment has gone and it's far easier to discover a reproducible reaction from a stimulus.

Skinner with his box.

Skinner's experiments involved a critter in a box, often a mouse, with a light, lever and food dispenser. In some experiments the floor was wired to give small static shocks. Experiments investigated what stimulus would cause the mouse to push the lever and how long for. Food appears when the light is on and the mouse presses the lever.

Change the food pellets to experience points or loot and you might start to look at WoW and freemium mobile phone games with new eyes!


  • Reward - the outcome of the behavior. For a mouse this is a food pellet. For a player it's more likely to be XP, loot or a new ability. (These are know as reinforcers. In Skinner's experiments the reward might be to negate something - like the reward of not being electrocuted.)

  • Requirement - the rules that determine when the reward is given. If the mouse pushes the lever when the light is on, they get a pellet. If the player kills 100 orcs, they get a level. (This is also known as the contingency.)

  • Response - The response to a stimulus in order to get the reward. A mouse might push a lever in response to a light to get the reward. A player looks inside newly discovered barrels in the hope of finding loot.

Behavioral Psychology and Video Games

We can use behavioral psychology to examine existing game mechanics. What are the rewards, requirements and responses in RPGs? How can we use these to design game mechanics? To deconstruct the rules of role-playing games, let's consider two questions:

  1. Why is the player taking action X?
  2. What action to we want the player to take?

A simple analysis of game mechanics from a behavioral psychology perspective might look as follows.


  • [Reward] - Gaining a level.
  • [Requirement] - A predefined XP is required to gain levels. XP is gained by killing monsters and completing quests.
  • [Response] - Player kills monsters and completes quests.


  • [Reward] - Player becomes more powerful.
  • [Requirement] - The fireplant in Mario is hidden in brick blocks. Walking on top of the power-up gives it to the player.
  • [Response] - Player hits the blocks, searching the levels for power-ups.


  • [Reward] - Game puts player at the top of the leaderboard, socially advertising their skill.
  • [Requirement] - Beat the game faster than current first entry on the leaderboard.
  • [Response] - The player continues to play the game trying to get on the leaderboard.

Requirement Types

The requirements can be set up in a few different ways.


After doing X tasks the player gets a reward. This is a fixed unchanging number. If the mouse presses the level 5 times they get a pellet. If the player collects 100 coins they get an extra life.

When using a requirement like this the player will mostly ignore the stimulus until they're quite close to the getting the reward. For instance in Mario, you passively collect coins until maybe you're at 90 then you'll probably hunt out those last 10 coins a little more actively.


After doing X tasks the player gets a reward. To get a second reward the player needs to do 2 * X tasks, then maybe 3 * X tasks and so on. An RPG usually has this kind of requirement to gain a level. The amount of XP you need for each successive level increases by a set ratio.


This is where things get interesting as it causes the reward to get dropped partially randomly. Random rewards give rise to compulsive behavior. This research has been directly applied to game design, especially in regards to mobile games.

Reward Rhythm

The requirements discussed above all incentivize the player to do X tasks before getting a reward.

If the time between the first task and the reward is long, the player may quit. Layering different types of requirement and reward drops keeps the player more engaged than just using a single requirement type. This is because the length to the next reward is somewhat unknown but probably not too far away.

Behavioral Contrast

In one experiment a chimpanzees is given a lever to pull, and each time they do, they get some delicious lettuce. The chimps are pretty happy with this because they like to eat lettuce. If the experiment is changed to give a grape just once, the next time the chimp gets lettuce they become irrationally annoyed and throw the lettuce at the experimenter.

A chimp enjoying delicious lettuce.

Reducing the reward after increasing it, is annoying for the player.

If you're killing slimes in the forest, gain a level, then suddenly the XP stops dropping you'd be annoyed.


Avoidance turns the idea of rewards on it's head and the subject works to avoid something happening.

Mice in the skinner box are given a static shock unless they push the lever. The mice quickly learn the minimum rate they need to push the lever and stick closely to that.

Ultima Online incentivizes the player to enter the game and visit their house regularly. If they didn't do this, the house would eventually decay and disappear! This has two results; it ensures the world isn't littered with abandoned houses and encourages players to keep coming back to the game.

This is similar to the economic term Loss Aversion. It is viciously exploited by freemium mobile games to make game "sticky" i.e. incentivize the player to return to the game.

Keeping Player's Engaged

Giving out rewards using a variable strategy keep players engaged for the longest time. Players play longest when they know something cool is coming "soon". A player is never going to quit if they know a reward is coming any second.

Layering reward schedules keeps player from ever wanting to quit because it always feels as if a cool reward is just about to drop. This effect can be made stronger by mixing in avoidance so the player is also working to stop something bad happening.

Make it easy for the player to switch between several activities. Perhaps leveling has slowed but there's places to explore, loot to discover etc.

Be sure to ask why you want to keep the player engaged. Your game should ideally stand on it's own without psychological tricks to force engagement!

End Notes

The key take away is behavioral psychology is a lens, you can use to look at your game. It's also a framework that can add or reduce player engagement in the game.

Take a critical look at your game and consider what reward-requirement-response loops already exist. Then consider if you like them and tweak as needed!

Interested in knowing more? Check out the article on some Skinner's laws of behavior.

Thanks to John Hopson for his excellent article on behavioral psychology and games available on Gamasutra here.