Hunger and socioeconomic background additively predict impulsivity in humans

Impulsivity refers to the valuation of future rewards relative to immediate ones. From an evolutionary perspective, we should expect impulsivity to be sensitive to the current state of the organism (for example, hunger), and also its long-term developmental history. There is evidence that both current hunger and childhood socioeconomic deprivation are individually associated with impulsivity, but it is not known how these combine. For example, acute hunger might over-ride social gradients in baseline impulsivity, or alternatively, individuals who have experienced greater deprivation might respond more strongly to acute hunger. We aimed to investigate whether hunger and childhood socioeconomic deprivation act additively or interactively in three studies utilising delay discounting tasks. Childhood socioeconomic deprivation was measured using childhood postcode and a self-report measure. In two studies hunger was experimentally manipulated (n = 95 & n = 93 respectively), and in the third we simply measured natural variation. We employed a standard hypothetical delay discounting task in two studies, and a behavioural task with experienced delays in the third (n = 330). Although the individual studies varied in which predictors were statistically significant, when we meta-analysed them, a clear pattern emerged. Hunger predicted greater impulsivity; childhood socioeconomic deprivation predicted greater impulsivity; and these two effects were additive rather than interactive.