Caption 
 
 This is the happiness equation, where t is the trial number, w0 is a constant term, other weights w capture the influence of different event types, 0 ≤ γ ≤ 1 is a forgetting factor that makes events in more recent trials more influential than those in earlier trials, CRj is the CR if chosen instead of a gamble on trial j, EVj is the EV of a gamble (average reward for the gamble) if chosen on trial j, and RPEj is the RPE on trial j contingent on choice of the gamble. The RPE is equal to the reward received minus the expectation in that trial EVj. If the CR was chosen, then EVj = 0 and RPEj = 0; if the gamble was chosen, then CRj = 0. The variables in the equation are quantities that the neuromodulator dopamine has been associated with in previous neuroscience studies. 

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 Today Screenshot from "The Great Brain Experiment" app. 
 
 The key to happiness could be low expectations — at least, that is the lesson from a new equation that researchers used to predict how happy someone would be in the future. 
 
 In a new study, researchers found that it didn't matter so much whether things were going well. It mattered whether they were going better than expected. 
 
 "It is often said that you will be happier if your expectations are lower,” Dr. Robb Rutledge, the senior research associate at University College London (UCL) who led the study, said in a statement. “We find that there is some truth to this: Lower expectations make it more likely that an outcome will exceed those expectations and have a positive impact on happiness.” 
 
 Not that you should walk around gloomy all of the time. Having expectations at all — say, for a lunch date with a friend — can lift your spirits “as soon as you make the plan,” Rutledge said. 
 
 But anticipating the greatest meal of your life could result in feeling pretty disappointed. No, this study was not meant to ruin your lunch plans. Instead, researchers wanted to figure out a way to give doctors a subjective, quantitative way to measure mood disorders. 
 
 The study involved two parts. First, 26 subjects made decisions that led to financial wins or losses, all while being monitored by an MRI machine. Later, 18,420 people played a game called “The Great Brain Experiment,” which replicated the experiment with points instead of money. 
 
 Ultimately, the researchers found that it was not the amount of total money or points won that mattered — it was how winning or losing stacked up to expectations formed during past experiences. 
 
 
 
 Today This is the happiness equation. 
 
 They even came up with a mathematical equation that could accurately predict how happy someone would be during the money experiment and while playing the smartphone game. Eventually, researchers said, it might be able to help doctors predict how people with mood disorders might react to the small wins and losses of everyday life. 
 
 The study was published in the Proceedings of the National Academy of Sciences. 
 
 Keith Wagstaff writes about technology for NBC News. He previously covered technology for TIME's Techland and wrote about politics as a staff writer at TheWeek.com. You can follow him on Twitter at @kwagstaff and reach him by email at: Keith.Wagstaff@nbcuni.com 
 
 
 
 
 
 
 

– How happy will you be at a given point in time? Scientists have come up with an equation to answer the question, or as they call it in the journal PNAS, "a computational and neural model of momentary subjective well-being." Mathematicians can marvel at the actual formula here. Laymen can simply remember this takeaway: Lower expectations can bring you more happiness, Today reports. In a series of tests on subjects, the researchers found that people are happiest when things turn out better than expected, happier even than they would be had expectations been high in the first place. But it's not just about your expectations at any given moment, a researcher from University College London tells the BBC. "All of the recent expectations and rewards combine to determine your current state of happiness." And all these factors get crunched in the fancy formula. "We can look at past decisions and outcomes and predict exactly how happy you will say you are at any point in time," says the researcher. The team proved the point by accurately predicting happiness levels of 18,000 users of a smartphone app called "The Great Brain Experiment." Researchers hope the findings can boost our understanding of mood disorders. (If all that's too complicated, try the pope's tips for happiness.)