Tag: prediction

Will we ever… predict earthquakes?

By Ed Yong | September 24, 2012 9:00 am

Here’s the 11th piece from my BBC column

On Friday, 11 March 2011, an earthquake struck the oceans near Tohoku, a region on Japan’s east coast. With a magnitude of 9.0, it was among the five most powerful earthquakes ever recorded, strong enough to shift the entire planet by several inches along its axis. It triggered a tsunami that killed thousands of people and wrecked the Fukushima-Daiichi nuclear power plant.

A quake that large shouldn’t have happened at Tohoku, at least not to the best of Japanese scientists’ knowledge. The hazard maps they had drawn up predicted that big earthquakes would strike in one of three zones to the south of the country – Tokai, Tonankai, and Nankai. No earthquake has hit these regions since 1975, while several have occurred in “low-probability” zones, such as Tohoku.

Japan isn’t alone. The incredibly destructive earthquakes that hit Wenchuan, China in 2008 and Christchurch, New Zealand in 2010 and 2011 all happened in areas deemed to be “relatively safe”. These events remind us that earthquake prediction teeters precariously between the overly vague and overly precise. At one extreme, we can calculate the odds that big earthquakes will strike broad geographic areas over years or decades – that’s called forecasting. At the other extreme, early warning systems can relay news of the first tremors to people some distance away, giving them seconds to brace themselves. But the ultimate goal – accurately specifying the time, location and magnitude of a future earthquake – is extremely difficult.

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Travels with dopamine – the chemical that affects how much pleasure we expect

By Ed Yong | November 12, 2009 12:00 pm

How would you fancy a holiday to Greece or Thailand? Would you like to buy an iPhone or a new pair of shoes? Would you be keen to accept that enticing job offer? Our lives are riddled with choices that force us to imagine our future state of mind. The decisions we make hinge upon this act of time travel and a new study suggests that our mental simulations of our future happiness are strongly affected by the chemical dopamine.

Dopamine is a neurotransmitter, a chemical that carries signals within the brain. Among its many duties is a crucial role in signalling the feelings of enjoyment we get out of life’s pleasures. We need it to learn which experiences are rewarding and to actively seek them out. And it seems that we also depend on it when we imagine the future.

Tali Sharot from University College London found that if volunteers had more dopamine in their brains as they thought about events in their future, they would imagine those events to be more gratifying. It’s the first direct evidence that dopamine influences how happy we expect ourselves to be.

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When we learn about new experiences, neurons that secrete dopamine seem to record the difference between the rewards we expect and the ones we actually receive. In encoding the gap between hope and experience, these neurons help us to repeat rewarding actions.

This was clearly demonstrated in 2006, when Mathias Passiglione showed that people’s ability to learn about rewards could be improved by giving them a drug called L-DOPA. It’s a precursor to dopamine, a sort of parent molecule that can increase the concentrations of its offspring. Passiglione asked volunteers to learn links between different symbols and different financial rewards. He found that under the influence of L-DOPA, they were better at picking the symbols that earned them the most cash.

Passiglione’s study was important, but his volunteers were forced to make a fairly artificial choice between two virtual symbols in a constrained lab setting. What happens in real life, when choices are complex and our decisions hinge on our ability to think about the future?

To answer that, Sharot recruited 61 volunteers and asked them to say how happy they’d feel if they visited one of 80 holiday destinations, from Greece to Thailand. All of the recruits were given a vitamin C supplement as a placebo and 40 minutes later, they had to imagine themselves on holiday at half of the possible locations. After this bout of fanciful daydreaming, they had to take another pill but this time, half of them were given L-DOPA instead of the placebo. Again, they had to imagine themselves in various holiday spots.

The next day, Sharot brought the volunteers back. By this time, they would have broken down all the L-DOPA in their system. She asked them to choose which of two destinations they’d like to go to, from the set that they had thought about the day before. Finally, they rated each destination again.

By the end of the experiments, they perceived their imaginary holidays to be more enjoyable if they had previously thought about the locations under the influence of L-DOPA (while vitamin C, as predicted, had no effect). The implication is clear: think about the future with more dopamine in the noggin and you’ll imagine that you have a better time.

Critically, this wasn’t because they were feeling happier in the actual moment. All the recruits filled in questionnaires about their emotional state every time they took a pill and these revealed that the dopamine boost didn’t actually affect the present state of mind. All it did was change their predictions of their future state of mind. These happier predictions affected their choices too – more often than not, they chose to travel to destinations that they had envisioned through dopamine-tinted goggles.

How dopamine has its way is unclear. Sharot suggests that it could boost how much we want something when we imagine it. Its effects could also tie into its role in learning. When we imagine the future, this chemical strengthens the link between what we think about and any feelings of enjoyment we might gain from it. This model fits with the fact that some neurons in the striatum become more active the more pleasure we expect from an experience.

Either way, it’s clear that our knowledge of dopamine’s myriad roles is just beginning. Broadening that knowledge is important for understanding our own behaviour, which, as Sharot says, “is largely driven by estimations of future pleasure and pain”.

Dopamine-graphs.jpg

Reference: Current Biology 10.1016/j.cub.2009.10.025

More on Sharot’s work and dopamine: 

 

 

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To predict what will make you happy, ask a stranger rather than guessing yourself

By Ed Yong | March 19, 2009 2:00 pm

Blogging on Peer-Reviewed ResearchWant to know how much you’d enjoy an experience? You’re better off asking someone who has been through it, even if they’re a complete stranger, than to find out information for yourself. This advice comes from Daniel Gilbert from Harvard University, who espoused it in his superb book Stumbling on Happiness. Now, he has found new support for the idea by studying speed-daters and people receiving feedback from their peers.

In the first study, he found that female students were better able to predict how much they would enjoy a speed-date if they listened to the experiences of strangers than if they make their own assessments based on available information. Likewise, the second study found that people more accurately foresaw their reactions to criticism when they knew how someone else had reacted than when they had the information for themselves.

This interesting result masks a second one of equal importance – people don’t believe that this works. In both cases, most volunteers felt that they would be better off relying on their own counsel than to lean on the opinions of others. In some ways, that’s not surprising – it is, after all, a fairly counter-intuitive idea. But it also comes on the back of a huge amount of evidence that we humans are really very bad at predicting what will make us happy.

Time and again, psychological studies have found that we overestimate how happy we will be after winning a prize, starting a new relationship or taking revenge against those who have wronged us. We also overrate our disappointment at bad test results, disability or failure to progress at work. Try as we might, we consistently fail to forecast our own emotional reactions, and we even fail to accurately remember our past experiences to be used as guides.

Gilbert says that the main reason for this is an inability to accurately imagine future events. We can close our eyes and try to picture ourselves in the future but we focus on the wrong things, we predict that our emotions will last longer than they do, and so on. Some scientists have tried to improve things by training people to mentally time-travel with more accuracy but these attempts have been largely unsuccessful.

Gilbert advocates a different ethos – use other people as living simulators. In most cases, you can find someone who has been through the same experience, and they can act as a mental surrogate. Having actually lived through the experience you’re trying to picture yourself going through, they are resistant to many of the mistakes we naturally make in our predictions.

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