It gets worse. Unbeknown to our subjects, we had instructed some of the interviewees to respond randomly to their questions. Though many of our interviewers were allowed to ask any questions they wanted, some were told to ask only yes/no or this/that questions. In half of these interviews, the interviewees were instructed to answer honestly. But in the other half, the interviewees were instructed to answer randomly. Specifically, they were told to note the first letter of each of the last two words of any question, and to see which category, A-M or N-Z, each letter fell into. If both letters were in the same category, the interviewee answered “yes” or took the “this” option; if the letters were in different categories, the interviewee answered “no” or took the “that” option.

Strikingly, not one interviewer reported noticing that he or she was conducting a random interview. More striking still, the students who conducted random interviews rated the degree to which they “got to know” the interviewee slightly higher on average than those who conducted honest interviews.

The key psychological insight here is that people have no trouble turning any information into a coherent narrative. This is true when, as in the case of my friend, the information (i.e., her tardiness) is incorrect. And this is true, as in our experiments, when the information is random. People can’t help seeing signals, even in noise.

There was a final twist in our experiment. We explained what we had done, and what our findings were, to another group of student subjects. Then we asked them to rank the information they would like to have when making a G.P.A. prediction: honest interviews, random interviews, or no interviews at all. They most often ranked no interview last. In other words, a majority felt they would rather base their predictions on an interview they knew to be random than to have to base their predictions on background information alone.

So great is people’s confidence in their ability to glean valuable information from a face to face conversation that they feel they can do so even if they know they are not being dealt with squarely. But they are wrong.

What can be done? One option is to structure interviews so that all candidates receive the same questions, a procedure that has been shown to make interviews more reliable and modestly more predictive of job success. Alternatively, you can use interviews to test job-related skills, rather than idly chatting or asking personal questions.

Realistically, unstructured interviews aren’t going away anytime soon. Until then, we should be humble about the likelihood that our impressions will provide a reliable guide to a candidate’s future performance.