Human complex exploration strategies are enriched by noradrenaline-modulated heuristics

An exploration-exploitation trade-off, the arbitration between sampling a lesser-known against a known rich option, is thought to be solved using computationally demanding exploration algorithms. Given known limitations in human cognitive resources, we hypothesised the presence of additional cheaper strategies. We examined for such heuristics in choice behaviour where we show this involves a value-free random exploration, that ignores all prior knowledge, and a novelty exploration that targets novel options alone. In a double-blind, placebo-controlled drug study, assessing contributions of dopamine (400 mg amisulpride) and noradrenaline (40 mg propranolol), we show that value-free random exploration is attenuated under the influence of propranolol, but not under amisulpride. Our findings demonstrate that humans deploy distinct computationally cheap exploration strategies and that value-free random exploration is under noradrenergic control.

Automated summary

The exploration-exploitation trade-off between sampling a lesser-known option against a known rich option has traditionally been solved using computationally demanding algorithms. However, research shows that humans may also deploy cheaper strategies, such as value-free random exploration and novelty exploration. A drug study involving dopamine and noradrenaline suggests that value-free random exploration is under noradrenergic control, highlighting the presence of distinct computationally cheap exploration strategies in humans.