A zero-intelligence trader (ZI) is a simple algorithmic trader in a market based on the dumb agent theory who proposes to purchase (bid) or to sell (ask) randomly, subject only to minimal constraints.
Under either interpretation, ZI traders use minimal intelligence in choosing their actions in markets.
[1] Simple double auctions tend to achieve high levels of allocative efficiency even when they are populated by zero-intelligence traders.
Specifically, any non-rationality of individuals does not necessarily carry over into outcomes of markets.
[2] The simple form of this algorithmic trader allows it to serve as a convenient tool to explore and identify properties that can be attributed to various kinds of market institutions.