In general, it is related to how the activity may or may not trigger the release of “good” neurotransmitters in your brain. And conversely, an activity that generates little or no positive neurotransmitters will be considered boring. One standard example is with dopamine, a neurotransmitter that makes us feel “good.” Any activity that generates it will often be considered fun. Knowing this, media producers are often honed in on creating little rewarding moments which trigger dopamine hits, thus telling our brain that the activity is fun. But not all brains are the same. Some people consume the same media and not get the same dopamine release and will thus find it boring. Adrenaline often has similar effects, thus why people often find sports, thrilling rides, or scary movies fun.
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