We analyse 10,920 shortest path connections between 105 members of an interviewing bureau, together with the equivalent conceptual, or ‘small world’ routes, which use individuals’ selections of intermediaries. This permits the first study of the impact of accuracy within small world chains. The mean small world path length (3.23) is 40% longer than the mean of the actual shortest paths (2.30), showing that mistakes are prevalent. A Markov model with a probability of simply guessing an intermediary of 0.52 gives an excellent fit to the observations, suggesting that people make the wrong small world choice more than half the time. © 2005 Elsevier B.V. All rights reserved.