Can a Test Tell You Whether You Have Trouble Remembering Faces? Prosopagnosia Testing

The CFMT (Cambridge Face Memory Test) is a performance-based test that examines how well someone can remember faces they've been shown. It's structured so that, after learning a set of faces, the person picks out the same individual from photos shown at different angles or under different lighting — and their accuracy rate produces a numerical score for face memory and identification.

One notable feature of the CFMT is that it can objectively measure actual face-recognition performance, without relying on self-report. In research and clinical evaluation, it's used, among other things, to compare the face-memory scores of people suspected of having developmental prosopagnosia against average performance.

The PI20 (20-item Prosopagnosia Index) is a 20-item, self-report questionnaire published by Shah and colleagues in 2015. It scores, based on the respondent's own answers, how much difficulty they experience with everyday face recognition — things like "finding it hard to recognize someone I know when I see them out in public" or "often mixing up characters in movies."

A Japanese-language version, the PI20-J (Japanese 20-item Prosopagnosia Index), was published by Nakashima and colleagues in 2020. It was developed by translating and validating the items from the original version for Japanese speakers, and it's also used in research and evaluation within Japan. Both the PI20 and PI20-J are questionnaires for organizing the difficulty a person feels they're experiencing — they don't directly measure objective performance the way the CFMT does.

The CFMT and the PI20 / PI20-J are tools of a different nature. The CFMT measures objective performance in face memory; the PI20 / PI20-J measure the degree of difficulty a person is aware of experiencing themselves. But neither test, on its own, confirms a diagnosis of prosopagnosia.

Research has pointed out that self-reported scores on tools like the PI20 don't always match objective performance on tools like the CFMT. Someone might feel strong everyday difficulty while scoring within the average range objectively — or, conversely, score poorly while being relatively unaware of it themselves. Because of this, evaluating prosopagnosia typically draws on multiple tests and questionnaires like these, combined with a clinical interview covering when the difficulty started and in what situations it shows up, to reach an overall judgment.