Flexible use of facial features supports face identity processing

People prioritise diagnostic features in classification tasks. However, it is not clear whether this priority is fixed or is flexibly applied depending on the specific classification decision, or how feature use behaviour contributes to individual differences in performance. Here we examined whether flexibility in features used in a face identification task supports face recognition ability. In Experiment 1, we show that the facial features most useful for identification vary – to a surprising degree – depending on the specific face identity comparison at hand. While the ears and eyes were most diagnostic for face identification in general, they were the most diagnostic feature for just 22% and 14% of identity decisions, respectively. In 3 subsequent experiments, we find that flexibility in feature use contributes to an individual’s face identity matching ability. Higher face identification accuracy was associated with being aware of (Experiments 2 4) and attending to (Experiments 3 4) the most diagnostic features for a specific facial comparison. This conferred an enhanced benefit relative to focusing on features that were diagnostic of face identity decisions in general (Experiment 4). We conclude that adaptability in information sampling supports face recognition ability and discuss theoretical and applied implications.