How we make decisions depends on how uncertain we
are
Flexible combination of reward information across
primates
Abstract
A fundamental but rarely contested assumption in
economics and neuroeconomics is that decision-makers compute subjective values
of risky options by multiplying functions of reward probability and magnitude.
By contrast, an additive strategy for valuation allows flexible combination of
reward information required in uncertain or changing environments. We
hypothesized that the level of uncertainty in the reward environment should
determine the strategy used for valuation and choice. To test this hypothesis,
we examined choice between risky options in humans and rhesus macaques across
three tasks with different levels of uncertainty. We found that whereas humans
and monkeys adopted a multiplicative strategy under risk when probabilities are
known, both species spontaneously adopted an additive strategy under
uncertainty when probabilities must be learned. Additionally, the level of
volatility influenced relative weighting of certain and uncertain reward
information, and this was reflected in the encoding of reward magnitude by
neurons in the dorsolateral prefrontal cortex.