Abstract
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.
Highlights
Impulsivity is a complex concept encompassing multiple behavioural components
As it has previously been suggested that hunger and measures of socioeconomic status may be associated (Nettle 2017) we initially ran a model to see if hunger was predicted by childhood Indices of Multiple Deprivation (IMD), whilst controlling for time since participants had last eaten, finding that time since a person had eaten did predict hunger but childhood IMD did not (Appendix, Table 5, Model 1)
As impulsivity measured via delay discounting is defined as the systematic devaluation of an outcome as the delay to its delivery increases, impulsivity is captured by the rate with which indifference point reduces as the delay increases
Summary
Impulsivity is a complex concept encompassing multiple behavioural components. High levels of impulsivity have been implicated in a range of negative health related behaviours, including, but not limited to, sexual risk-taking (Donohew et al 2000), smoking and heavy drinking (Granö et al 2004), and drug abuse (de Wit 2009). There is evidence that those who show lower levels of impulsivity may be protected against weight gain (Duckworth et al 2010), suggesting that interventions focussing on manipulating impulsivity could be beneficial for public health. For this reason it is important to understand factors which may underlie the emergence of impulsive behaviours. Delay discounting involves the systematic devaluation of an outcome as the delay to its delivery increases; more impulsive individuals devalue at a higher rate. Measurement of delay discounting involves repeated choices between smaller but more immediately available rewards (smaller-sooner rewards - SSRs) and larger but more delayed rewards (larger-later rewards - LLRs)
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