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There's a downside to the upside, and believe it or not, an upside to the downside. Here's why considering the worst case might lead to better outcomes.

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As a SciShow viewer, you can keep building your STEM skills for 20% off an annual premium subscription at Believe it or not, researchers are working on ways to make people more pessimistic, and that’s a good thing.

Even though we’re always told to see the glass half-full, people who prioritize the downside of decisions tend to make more beneficial ones in the long run. Those are the pessimists. Optimists generally have brains that favor the upside of a decision.

Sometimes, the consequences of optimistic tendencies are mild, like going outside without a jacket on a potentially rainy day and getting wet. But they can also be more serious, like spending money that you don’t have. And when it comes to deciding whether to engage in extremely risky behaviors, a brain that’s wired to ignore the downsides of a decision can have life or death consequences. [♪ INTRO] On average, we begin our lives as optimists.

Not just in general, but in relation to the specific decisions we make. And, being scientists, a team of researchers at University College London have come up with a mathematical equation to define what optimism is, because everything is quantifiable if you try hard enough. Let’s say you’re about to walk out your front door.

Then you look at your phone and it says there’s a 60% chance of rain. This data is put into the equation as your chance of staying dry: 1 minus 0.6, which is 0.4. If you think that you don’t need a raincoat because you actually have more of a 70% chance of staying dry, the researchers would include 0.7 as your prediction of staying dry.

The optimism score just subtracts the initial data from your prediction, giving you a score of 0.3. So you’d have an optimism score above zero, meaning these researchers would categorize you as an optimistic person. And that tracks because you predicted a higher chance of staying dry than the information your phone gave you.

Most of us start out life prioritizing the upside of a decision, like not having to deal with a raincoat, and downplaying the downside that you might get wet. But many of us don’t retain that optimism into adulthood. And it’s not just the weight of life’s responsibilities that beats the optimism out of us.

It’s our maturing brains. As we age, more of us begin considering the downside of decisions. This is the foundation of pessimism, or a score below zero in that equation.

And it can be a good thing when it keeps you from being cold and wet. So, to compare younger brains to adult brains, the researchers at University College London gave a bunch of people short scenarios, like getting caught in the rain, and asked them what they thought the likelihood of that happening to them would be. Then the researchers gave them the real odds of those things happening to a person, and asked again.

The researchers used the optimism equation to determine which participants were optimistic and which were pessimistic. And they found that all of the participants were good at incorporating the upside in their decision-making. So they all thought about the hassle they’d avoid by not lugging around a raincoat.

But not all of them were good at incorporating the downsides of their decisions. And that was particularly true for the younger participants. Young people don’t necessarily think of themselves as more invincible than older people, but they’re more optimistic about the outcome.

A young person might think, “So what if I get wet?” while an older person might think back to how miserable they were last time they forgot their jacket. And there’s neurological evidence for this tendency. Brain scans show us how optimistic people tend to ignore the bad and focus on the good.

Using magnetic resonance imaging, the team in London discovered a neural pathway in the brain that reinforces the upside of a decision and rejects the downside. The parts of your brain connected by this pathway are known to be involved in this kind of decision-making. They’re called the inferior frontal gyrus, or IFG, and the striatum.

The researchers noticed that people who responded to the good and not the bad outcomes, AKA the optimists, had more reinforced pathways between the IFG and the striatum. There was a thicker insulating layer called myelin around the brain cells that form those pathways, which allows faster signals to be sent between those parts of the brain. So scientists are finding physical signs of optimism in the brain.

But a pathway is nothing without the chemicals traveling it. And the main chemical traveling along that pathway is dopamine, the classic reward chemical. That makes sense because optimism and pessimism are all about predicting whether you’ll win in the end.

But dopamine doesn’t just have one job. Once it gets to either end of the pathway, it can bind to a variety of receptors in your brain to produce a bunch of different responses. The different receptors that dopamine binds to regulate how you process positive and negative information.

There are D1 receptors and D2 receptors, and they seem to have opposite effects. When dopamine binds to D1 receptors, it tends to help you focus on the upside of a decision. When it binds to D2 receptors, it tends to help you focus on the downside.

Scientists have suggested that D1 receptors take the driver’s seat in the part of the brain with the IFG, and D2 receptors do so in the striatum. So D1 receptors in the IFG might be in control of optimism, while D2 receptors in the striatum might be in control of pessimism. That means the same dopamine can lead to optimism or pessimism depending on where it ends up.

Ultimately, those D2 receptors in the striatum could help you be a little more careful because you’d end up nice and dry when it rains. But life’s decisions get more serious than that. Which explains why scientists might want to understand these pathways better, maybe even leading to future interventions for people who don’t naturally consider the downsides of their decisions.

The University College London study experimentally made adults more pessimistic using a technique called transcranial magnetic stimulation. The researchers put magnets on the participants’ heads and stimulated their IFG’s while they completed the first experiment again: the one where they’re asked what they think the likelihood of them getting caught in the rain is. They used a magnetic field to create an electric signal in the IFG and made it temporarily stop working the way it otherwise would.

That intervention made people respond to the test questions as pessimists. Amazingly, the participants changed their decision making in favor of the downside. When told that there was a 70% chance of rain, they’d guess that they had more of a 80% chance of getting wet.

The researchers think that the IFG not only promotes optimistic thinking, but also stops pessimistic thinking. So disrupting that interaction allowed pessimistic thought to manifest itself. Ultimately, all these chemicals in your brain whooshing between the IFG and the striatum and binding to different receptors really do influence how pessimistic or optimistic you are.

But an inability to incorporate the downsides of a decision can have more serious implications than the hypothetical situations in that experiment. And while no one is suggesting that these neural circuits are the sole cause of dangerous behaviors, the authors of the University College, London paper believe that a predisposition to make optimistic decisions could be a factor. So there’s a lot that goes into your pessimistic decisions, but they might just change your life for the better.

With so much complicated stuff going into decision-making, it’s great that we have Brilliant to help us understand it a little better. Brilliant is an online learning platform with courses in science, computer science, and math. They provide all kinds of interactive puzzles and lessons for learners at all levels.

And their course on Logic can help you work out what to do when you’re in the worst case scenario or given false information. They walk you through the process of elimination and making predictions. Okay, so it’s all math.

But critical thinking skills are the basis for mathematical logic! Find out what I’m talking about by clicking the link in the description down below or heading to As a SciShow viewer, you get 20% off an annual premium subscription.

Thanks for watching this SciShow video and thanks to Brilliant for supporting it! [♪ OUTRO]