Timing matters: primacy effects of experience on mood revealed using a novel Mood-Machine-Interface

Mood is thought to integrate across our experiences, yet we do not know how the relative timing of past events shapes how we feel in the moment. Here, we investigate the relationship between the timing of previous experiences and mood by combining a novel closed-loop mood controller alongside computational modelling and neural data. We first present the development of a Mood Machine Interface which allows us to individualize rewards in real-time in order to generate substantial mood transitions, across healthy as well as depressed, adolescents and adults. We then show that early-experiences have a larger effect on mood than recent ones, and that the longer one is exposed to a given context, the harder it is for new events to change mood. We find that ACC neural activity underlies the influence of early experiences on mood. This provides a neuro-computational account of mood regulation by early events and suggests new directions for individualized mood interventions.