6. Variable Interval Limited Hold

Description: The first response after a variable interval of time is reinforced, providing the response occurs within a set period at the end of the interval.
Produces:

• A high steady rate until reinforced
• No (or only small) post-reinforcement pause
• Less strain with large increases in average interval that fixed interval limited hold.
• High RTE

Examples in natural environments

• Telephoning a friend when the line is busy. As long as friend is on the phone, the line is busy. You only get through after the call is over, but if you wait too long, your freind may leave the phone or receive another call.
• Cooking when you are uncertain of the time it will take to cook. You are uncertain of when it will be done, but if you leave it too long, it will burn.
• Lions hunting from a position of ambush. If they wait long enough, some prey will come by, but they have to attack as soon as it does; otherwise it will escape.
  

Examples in video games

• Waiting for a monster to re-spawn on a crowded server. If monsters re-spawn at variable intervals the player must wait for a fixed period of time to kill the monster. However, if they are not there at the time the monster re-spawns the monster is likely to be killed by another player.
• Obtaining objects, treasures, or power-ups that only appear for a limited time at random times.