The VTA is the component that detects a stimulus and determines whether it was positive or negative, something to be encouraged or avoided. It then signals its decision to the NAc, which causes the appropriate response to be experienced. So if you eat a tasty snack, the VTA registers this as a good thing, tells the NAc, which then causes you to experience pleasure and enjoyment. If you accidentally drink rotten milk, the VTA registers this as a bad thing and tells the NAc, which causes you to experience revulsion, disgust, nausea, practically anything the brain can do to ensure you get the message, “Do not do that again!” This system, when taken together, is the mesolimbic reward pathway.
“Reward” in this context means the positive, pleasurable feelings experienced when we do something our brain approves of. Typically, these are biological functions, like eating food if hungry, or when said foods are nutrient or resource rich (carbohydrates are a valuable energy source as far as the brain is concerned, hence they can be so difficult to resist for dieters). Other things cause much stronger activation of the reward system: things like sex; hence people spend a lot of time and effort to obtain it, despite the fact that we can live without it. Yes, we can.
It doesn’t even have to be anything so essential or vivid. Scratching a particularly persistent itch gives pleasurable satisfaction, which is mediated by the reward system. It’s the brain telling you that what just happened was good, you should do it again.
In the psychological sense, a reward is a (subjectively) positive response to an occurrence, one that potentially leads to a change in behavior, so what constitutes a reward can vary considerably. If a rat presses a lever and gets a bit of fruit, it’ll press the lever more, so the fruit is a valid reward.25 But if instead of fruit it gets the latest Playstation game, it is unlikely to press the lever more frequently. Your average teenager might disagree, but to a rat a Playstation game is of no use or motivational value, so it’s not a reward. The point of this is to emphasize that different people (or creatures) find different things rewarding—some people like being scared or unnerved, while others don’t and can’t see the appeal.
There are several methods via which fear and danger can become “desirable.” To begin with, we are inherently curious. Even animals such as rats have a tendency to explore something novel when presented with the opportunity. Humans even more so.26 Consider how often we do something just to see what happens? Anyone who has children will certainly be familiar with this often-destructive tendency. We are drawn to novelty value. We are faced with a huge variety of new sensations and experiences, so why go for the ones that involve fear and danger, two bad things, rather than the many benign-but-equally-unfamiliar ones?
The mesolimbic reward pathway provides pleasure when you do something good. But “something good” covers a very wide range of possibilities, and this includes when something bad stops happening. Due to adrenalin and the fight-or-flight response, periods of fear and terror are incredibly vivid, where all your senses and systems are alert and poised for danger. But, usually, the source of the danger or fear will go away (especially given our overly paranoid brains). The brain recognizes that there was a threat, but now it’s gone.
You were in a haunted house, and now you’re outside. You were hurtling through the air on the way to certain death, but now you’re on the ground and alive. You were hearing a terrifying story, but now it’s finished and the bloodthirsty serial killer never appeared. In each case, the reward pathway is recognizing danger that suddenly ceases, so whatever you did to stop the danger, it’s vitally important that you do that next time. As such, it triggers a very powerful reward response. In most cases, like eating or sex, you just did something to improve your existence in the short term, but here you avoided death! This is far more important. On top of this, with the adrenalin of a fight-or-flight response coursing through our systems everything feels enhanced and heightened. The rush and relief that follows a scare can be intensely stimulating—more so than most other things.
The mesolimbic pathway has important neuronal connections and physical links to the hippocampus and the amygdala, allowing it to emphasize memories for certain occurrences it considers important and attach strong emotional resonance to them.27 It not only rewards or discourages behavior when it happens; it makes sure that the memory for the event is also particularly potent.
The heightened awareness, the intense rush, the vivid memories; all of this combined means that the experience of encountering something seriously scary can make someone feel more “alive” than at any other time. When every other experience seems muted and mundane in comparison, it can be a strong motivator to seek out similar “highs,” just as someone used to drinking double-strength espresso won’t find an extra-milky latte especially fulfilling.
And, quite often, it has to be a “genuine” thrill, rather than a synthetic one. The conscious, thinking parts of our brain might be easily fooled in many cases (many of them covered in this book), but they’re not that gullible. As such, a video game where you drive a high-speed vehicle, no matter how visually realistic, can’t hope to provide the same rush and sensation as actually doing it. The same goes for fighting zombies or piloting starships; the human brain recognizes what’s real and not real, and can cope with the distinction, despite what the old “video games lead to violence” arguments suggest.