Why do people exhibit preferences even in the most symmetric settings? Why these biases are different between individuals? Lebovich and colleagues characterize these biases and present theoretical evidence that even in an idealized experiment, in which the settings are symmetric, idiosyncratic choice bias emerges from the dynamics of competing neuronal networks. These results suggest that idiosyncratic choice biases reflect the microscopic dynamics of choice and, therefore, are virtually inevitable in any comparison or decision task.