The Self-Serving Biases and Beliefs about Rationality

Most previous experiments attempting to establish the existence of the self-serving bias have confounded it with strategic behavior. We design an experiment that controls for strategic behavior (Haman effects) and isolates the bias itself. The self-serving bias that we measure concerns beliefs about the rationality of others. We find very limited support for the existence of the bias. To help understand why the bias seems to hold in some settings but not in others, we discuss a distinction between biases that are self-serving and those that are actually self-defeating.