NEW PAPER: Dopamine and reward uncertainty in gambling addiction

Martin Zack, Ross St George and I have a new article on the role of dopamine in signalling uncertain reward, as a central mechanism in gambling addiction, in a special issue on gambling in PNBP. 50 copies sharelink here

Just because something activates dopamine (e.g. gambling, video games, pizza, hot bath), how would this become addictive? Tonic activity of DA by random rewards (i.e. the variable ratio) – as shown eg Fiorillo et al 2003 – may set scene for sensitization & escalating learning. We consider the evidence for this as a mechanism in problem gambling. This is not easy to test! 1) dopamine is hard to measure in humans, 2) it’s even harder to get handle on tonic dopamine. Nevertheless, there are several lines of supporting research, DA PET, fMRI, DA pharmacology. Three ideas in here that we’re particularly excited about. First, the resolution of reward uncertainty is crucial e.g. great work by Shen & Hsee – without resolution, reward uncertainty isn’t all that. Second, various EGM product features including speed, sensory feedback near-misses, losses disguised as wins, & opportunity for illusory control may harness and amplify these processes. Third, uncertainty can be layered: in Fiorillo et al 2003, the dopamine response was greatest at 50% reward but also when SIZE of reward was max variable. Uncertainty can also be added in timing of reward & by creating many reward variants (eg loot box prizes).

Zack M, St George R, Clark L. Dopaminergic signalling of uncertainty and the aetiology of gambling addiction [review]. Progress in Neuropsychopharmacology & Biological Psychiatry, 2020, 99: 109853, doi: 10.1016/j.pnpbp.2019.109853