Intrinsic reinforcement is a reward-driven behavior that comes from within an individual. With intrinsic reinforcement, an individual continues with a behavior because they find it personally rewarding, not out of fear of punishment or for an external reward.
Hobbies are often activities that bring intrinsic reinforcement. Some individuals complete crossword puzzles because they enjoy the sense of accomplishment, while others defeat a certain level of a video game for the internal reward of completing the game. Students study a topic to gain mastery of the subject, and still others may climb a mountain out of sheer self-determination. While both types of reinforcement help to bring a desired behavior, from a psychological standpoint, these intrinsic reinforcements provide stronger motivation than extrinsic ones.
Humans and other living organisms exhibit certain behaviors because doing so brings a reward. A laboratory rat learns to press a lever because it releases a pellet of food. A dog stands up and begs because its owner gives it a treat. A child throws a tantrum in the store to get his way, and an adult goes to a job he does not like because it provides a paycheck. These are all examples of extrinsic rewards or reinforcement. However, intrinsic reinforcement causes the individual to perform a task because it brings an inherent satisfaction.