The happiness of over 18,000 people worldwide has been predicted by a mathematical equation developed by researchers at UCL, with results showing that moment-to-moment happiness reflects not just how well things are going, but whether things are going better than expected.

The study, published in the Proceedings of the National Academy of Sciences, investigated the relationship between happiness and reward, and the neural processes that lead to feelings that are central to our conscious experience, such as happiness. 

A better understanding of how mood is determined by life events and circumstances, and how that differs in people suffering from mood disorders, could lead to more effective treatments. Research examining how and why happiness changes from moment to moment in individuals could also assist governments who deploy population measures of wellbeing to inform policy, by providing quantitative insight into what the collected information means

The scientists built a computational model in which self-reported happiness was related to recent rewards and expectations. The model was then tested on 18,420 participants in the game ‘What makes me happy?’ in a smartphone app developed at UCL called ‘The Great Brain Experiment’


The team, including Dr Nikolina Skandali (Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology), Prof Peter Dayan (UCL Gatsby Computational Neuroscience Unit), and Prof Ray Dolan (Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, and the new Max Planck UCL Centre for Computational Psychiatry and Ageing), used functional MRI to demonstrate that neural signals during decisions and outcomes in the task in an area of the brain called the striatum can be used to predict changes in moment-to-moment happiness. 

The striatum has a lot of connections with dopamine neurons, and signals in this brain area are thought to depend at least partially on dopamine. These results raise the possibility that dopamine may play a role in determining happiness.

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