Recognizing face sketches by a large number of human subjects: A perception-based study for facial distinctiveness

Understanding how humans recognize face sketches drawn by artists is of significant value to both criminal investigators and researchers in computer vision, face biometrics and cognitive psychology. However, large scale experimental studies of hand-drawn face sketches are still very limited in terms of the number of artists, the number of sketches, and the number of human evaluators involved. In this paper, we reported the results of a series of psychological experiments in which 406 volunteers were asked to recognize 250 sketches drawn by 5 different artists. The primary findings are: (i) Sketch quality (artist factor) has a significant effect on human performance. Inter-artist variation as measured by the mean recognition rate can be as high as 31%; (ii) Participants showed a higher tendency to match multiple sketches to one photo than to second-guess their answers. The multi-match ratio seems correlated to the recognition rate, while second-guessing had no significant effect on human performance; (iii) For certain highly recognized faces, their rankings were very consistent using three measuring parameters: recognition rate, multi-match ratio, and second-guess ratio, suggesting that the three parameters could provide valuable information to quantify facial distinctiveness.