Ambiguity Aversion: Implications for the Uncovered Interest Rate Parity Puzzle

High interest rate currencies tend to appreciate in the future relative to low interest rate currencies instead of depreciating as uncovered interest parity (UIP) predicts. I construct a model of exchange rate determination in which ambiguity-averse agents face a dynamic filtering problem featuring signals of uncertain precision. Solving a max-min problem, agents act upon a worst-case signal precision and systematically underestimate the hidden state that controls payoffs. Thus, on average, agents next periods perceive positive innovations, which generates an upward re-evaluation of the strategy's profitability and implies ex post departures from UIP. The model also produces predictable expectational errors, negative skewness, and time-series momentum for currency speculation payoffs.