The quality of the judicial system depends upon the quality of decisions th
at judges make. Even the most talented and dedicated judges surely commit o
ccasional mistakes, but the public understandably expects judges to avoid s
ystematic errors. This expectation however, might be unrealistic. Psycholog
ists who study human judgment and choice have learned that people frequentl
y fall prey to cognitive illusions that produce systematic errors in judgme
nt. Even though judges are experienced, well-trained, and highly motivated
decision makers, they might be vulnerable to cognitive illusions. We report
the results of an empirical study designed to determine whether five commo
n cognitive illusions (anchoring, framing, hindsight bids, the representati
veness heuristic, and egocentric biases) would influence the decision-makin
g processes of a sample of 167 federal magistrate judges. Although the judg
es in our study appeared somewhat less susceptible to two of these illusion
s (framing effects and the representativeness heuristic) than lay decision
makers, we found that each of the five illusions we tested had a significan
t impact on judicial decision making. Judges, it seems, are human. Like the
rest of us, their judgment is affected by cognitive illusions that can pro
duce systematic errors in judgment.