Fixed Interval (FI) and Variable Interval (VI) Schedules

Fixed Interval (FI) and Variable Interval (VI) schedules of reinforcement are also used to describe patterns of reward distribution that can influence player behavior and engagement.

Fixed Interval (FI) A fixed interval schedule provides reinforcement after a set period of time has passed, regardless of how many times the behavior is performed during that interval. This can be seen in games where rewards are given at regular, predictable intervals.

Many games offer daily login rewards and daily tasks to encourage players to return to the game each day. The reward is given after a 24-hour cycle, irrespective of how many times the player logs in during that period. This can create a habit-forming effect, as players might check in daily just to claim their rewards, even if they don’t play the game otherwise. It has to be said that this is strikingly similar to office workers clocking in every day.

In contrast to ratio schedules, FI schedules provide reinforcement after a set amount of time has passed, regardless of the number of responses. This can lead to a scalloped response pattern, where the behavior rate decreases immediately after reinforcement and then gradually increases as the next reinforcement approaches. Since the reinforcement is based on time, players can predict when the next reward will be available, which might lead to waiting behavior or checking in right before the expected reward time, try to minimize the time that might be wasted.

Variable Interval (VI) A variable interval schedule delivers reinforcement after an unpredictable amount of time has elapsed. This uncertainty can increase the frequency of the desired behavior, as players are less likely to stop checking for rewards because they don’t know when the next one will come.

In games like World of Warcraft, random world events can trigger at any time, providing unexpected rewards to players who happen to be present. These events might occur every few hours, but the exact timing is unknown, which encourages players to stay logged in or return frequently to avoid missing out on potential rewards.

VI schedules generally produce a high and steady rate of responding because the unpredictability of reinforcement discourages pauses in behavior. Behaviors maintained by VI schedules are more resistant to extinction (the stopping of reinforcement) than those maintained by other schedules because the expectation based on past experiences does not allow players to predict when reinforcement will stop.

In Mobile Farming Games: Fixed Interval: Games like Hay Day have crops that mature at fixed intervals (e.g., corn takes 4 hours to grow). Players must return at specific times to harvest their crops and continue progressing.

Variable Interval: Some games introduce pests or weather events that can affect crops at unpredictable times, requiring players to monitor their farms more frequently to protect their investments.

In MMORPGs: Fixed Interval: In Final Fantasy XIV, crafting materials regenerate at fixed times, incentivizing players to check back regularly to collect them. Variable Interval: Treasure chests or rare mobs that spawn at irregular intervals in open-world areas can lead to players exploring these areas more frequently and for longer durations, hoping to encounter the next spawn.