Since its release by King in 2012, Candy Crush Saga has been played by millions (if not more) of users worldwide (Curry, 2021). According to the Huffington Post, there were 93 million daily users of Candy Crush Saga in 2017 (Casti, 2017). This game has gained popularity due to its addictive nature that has its users keep coming back for more (King, 2012). You may ask, what makes this game so addicting? After playing this game for several minutes, it was clear to me that the addictive nature of Candy Crush Saga stems from the use of classical and operant conditioning in its game development.

     According to Wells (2014), Classical conditioning occurs when a neutral stimulus (NS) is paired with an unconditioned stimulus (US) and elicits an unconditioned response (UR). Over time, the NS becomes a conditioned stimulus (CS) that produces a conditioned response (CR). Ivan Pavlov and his salivating dogs are the most famous example of this form of conditioning. Pavlov paired the sound of a bell (NS) with food (US) which resulted in the dog salivating (UR). After a certain amount of time, the dog began to droll (CR) from the sound of the bell (CS) before seeing the food (US). The dog has learned that the bell is sounded before he receives food and therefore changed his natural behavior and began to drool to the bell's sound.  

     As seen above, classical conditioning is a technique used to shape behavior. This technique is commonly implemented in gaming applications such as Sugar Crush Saga. The moment you launch Sugar Crush Saga, positivity showers you. The opening page contains a happy cartoon with cheerful background music, images, and typography. According to Wells (2014), all these elements are considered an Unconditioned stimulus that can elicit an Unconditioned response (in this case, joy). Since these unconditioned stimuli are carried into the actual game, the repetition of pairing the game actions and the joyful theme causes users to associate playing the game and joy. In other words, the neutral stimulus of game actions (such as swiping) eventually becomes a controlled stimulus that elicits a controlled response of joy.  

     This example of classical conditioning alone would not be enough to have users addicted to this game. Therefore, the King developers included more classical conditioning instances in their game, such as a points system. When playing the game, you are awarded extra points if you complete the round with extra possible moves. Once you play the game for long enough, you learn that the points are used for a weekly ranking system for all the Candy Crush Saga players. You can gain more points and finish the round faster by using special candies that are created by matching more than three items at once. After each round, the leaderboard pops up, and after a while, you will unconsciously begin to associate matching larger sets of candies (CS) with landing on that leaderboard (CR).  

     When classical conditioning is coupled with operant conditioning, that's when users get hooked. Wells (2014) explains operant conditioning (also known as instrumental conditioning) as a behavior that results from consequences from one's environment. This consequence can either include a reward or a punishment, and it can be positive or negative (Sorgendal & Boks, 2014; Wells, 2014). B.F Skinner introduced this form of conditioning, with his findings on the Skinners box (Sorgendal & Boks, 2014). In this experiment, a rat was given reinforcement of a food pellet when it pressed down on a lever, Skinner found that the presence of this positive reinforcement caused the rat to press the lever again. According to Weinschenk (2011), Skinner also tested different reinforcement schedules during the experiment and found four possible schedules: fixed interval, variable interval, fixed ratio, and variable ratio. Skinner found that these reinforcement schedules elicit different kinds of behaviors from his rats (Weinschenk, 2011). Practically speaking, if you want to control the way someone learns something and how they will behave, you should consider which of these schedules will elicit the behavior you desire. 

     When you play Candy Crush Saga, you may notice the presence of three of these schedules: variable ratio, fixed ratio, and fixed interval. The variable ratio is the most addictive of these three schedules and can lead to rapid response rates (this is used in gambling) (Song et al., 2020; Weinschenk, 2011). Fixed ratio scheduling is also quite powerful, but according to Song et al. (2019), the response rates are more "stable and moderate"(para. 3). Fixed interval is less potent than the other two reinforcement schedules, but it still provides some form of behavioral change. It has been found that the desired behavior increases right before the fixed reward is given in a fixed interval schedule, which can be extremely valuable if coupled with the other two schedules (Cherry, 2020).  
     I have seen two different instances of variable ratio from the short amount of time that I have played Candy Crush Saga. The variable-ratio is used to create near misses as well as to provide users with positive feedback. Every time I have lost in Candy Crush Saga, I have lost by one or two moves and not more. This near-miss causes me to play again since I was "so close" to winning the first time. Harrigan (2009), in her study of the addictive nature of slot machines, explains near misses and reinforcement. When users only match up two out of the three items in a slot machine, it leads them to believe that they can get all three items if they play again. These users are motivated by the reinforcement (winning and joy) they will receive if they match all three, and since they are incredibly close to their goal, it reinforces their current efforts and encourages them to try again. Additionally, they know that they will receive a different board if they play again and have a higher chance of winning (since wins are calculated using the variable-ratio). 
     Like slot machines, when you nearly win in Candy Crush Saga, you are reinforced by the fact that you almost won and are therefore encouraged to try again and again (because you know if you do win, you will be able to advance to the next level). You are assuming that playing again will cause you to win since you were so close. This phenomenon is caused by variable ratio since the candies on the board differ each round and seem to be programmed so that some rounds provide a higher probability of winning than other rounds (you receive more possible matches). This causes users to play another game immediately after experiencing a near miss because they know that they will receive a different board and perhaps have a higher chance to win the game if they play again. 

     The second instance of variable ratio is seen with the feedback system in Candy Crush Saga. When you first start the game, you receive constant feedback on your moves ("sweet," "tasty"), but as the game progresses, you receive less and less feedback at a randomized rate. This feedback seems to be given after you score an average number of points (and this differs from round to round). Users seek to hear feedback because that is a natural human tendency (Anseel & Lievens, 2007), and since they do not know precisely when they will get it, it motivates them to try harder to receive it (Sorgendal & Boks, 2014). 

     The use of fixed ratio is used many times in Candy Crush Saga. Firstly, it is used to inform users at the beginning of each round as to how many points or objects they need to gather to win the game (the reinforcer is the completion of the round that elicits a sense of joy). This reinforcement is fixed since repetition of the same level will require the same number of points or objects to receive the reinforcer. The second is seen by the number of candies you need to pair in order to have the items disappear or to create a new special candy. Both of these instances are examples of positive reinforcement since you will receive points every time for completing these actions and matching four candies will always give you the same special candy every time (Sorgendal & Boks, 2014). Another example involves the gel box levels. The removal of the boxes requires users to match a minimum of three nearby candies. The reinforcement, in this case, is actually negative since the removal of the box gives you the sensation that you are close to winning and pushes you to continue the round (the feedback pane that displays a smaller number of boxes left to remove serves as a reinforcer). 

     Fixed intervals are used in Candy Crush Saga to give users an extra life every six hours and to give them a spin on the “booster wheel” every 24 hours. The number of hours does not change for both situations, and they are therefore fixed. Users receive an extra life as a reinforcement for having the game downloaded, and the reinforcement is positive since they are gaining something (an extra life). This motivates users to revisit the game when they know they have an extra life and can play the round that they recently lost. This concept is also applied to the "booster wheel" that allows you to spin a wheel for a useful game tool every 24 hours. Again, this is fixed and causes users to check back every 24 hours to spin the wheel and perhaps to play the game following the spin in order to use the new reward. As you can see, both of these strategies cause a form of addiction that has users returning to the app in order to receive the reward. 

     A synthesis of both operant and classical conditioning can be used further in Cady Crush Saga in order to flip more users into paying for games. The application of the most powerful schedule -variable-ratio- can be used to flip these users. For example, this schedule has proven the fact that unpredictable reinforcement is extremely effective and addictive (Sorgendal & Boks, 2014). Therefore, this app should present a pop-up that tells users that they can only purchase this pop-up when they are presented with it (it is not available at the store). This will make the pop-up feel like a reward (since it is not always available) and create a sense of urgency to buy the pop-up. To strengthen the pop-up even more, it should include three exclusive and mysterious candies available for purchase, that users will only be privy to once the game randomly gives it to them. This again creates a sense of urgency and curiosity and will cause users to buy the candies in order to find out there mysterious powers. If users purchase these pop-ups and like them, they will start to condition the purchasing of pop-ups with excitement and reward (classical conditioning). This may cause users to purchase other pop-ups in the future once this response becomes conditioned.  
     As you can see, this game is extremely addicting and uses many phycological learning strategies to grab the users.  Pavlov and Skinner would not have dreamed that their findings on classical and operant conditioning could have gone this far to captive millions of game players around the world. Now that you are privy to the different reinforcement schedules and the concept of classical conditioning, you can protect yourself from falling into the addictive trap of Candy Crush Saga.

Anseel, F., & Lievens, F. (2007). The Relationship Between Uncertainty and Desire for Feedback: A Test of Competing Hypotheses. Journal of Applied Social Psychology, 37(5), 1007–1040.  

Casti, T. (2017, December 7). More People Play 'Candy Crush' Than Live In These Places. HuffPost.  

Cherry, K. (2020, May 6). This Is Why You May Clean Your Teeth More Right Before a Dental Exam. Verywell Mind.  

Curry, D. (2021, March 19). Candy Crush Revenue and Usage Statistics (2021). Business of Apps.,%20more%20than,Saga%20generated%20$4.2%20million%20per%20day%20in%202018.  
Harrigan, K. A. (2009). Slot Machines: Pursuing Responsible Gaming Practices for Virtual Reels and Near Misses. International Journal of Mental Health and Addiction, 7(1), 68–83.  

King. (2012, November 13). ‎Candy Crush Saga. App Store.  
Song, K., Takahashi, S., & Sakurai, Y. (2020). Reinforcement schedules differentially affect learning in neuronal operant conditioning in rats. Neuroscience Research, 153, 62–67. 
Sorgendal, I., & Boks, C. (2014). Challenging interfaces are more fun! Operant conditioning for the interaction designer. International Journal of Learning Technology, 9(2), 94.  

Weinschenk, S. (2011). 100 Things every designer needs to know about people. Peachpit Press/New Riders.  

Wells, V. K. (2014). Behavioural psychology, marketing and consumer behaviour: a literature review and future research agenda. Journal of Marketing Management, 30(11–12), 1119–1158. 
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