Abstract
Familiarity for never-before-seen faces is a phenomenon tied to both visual perception and personal experience (Lyon, 1996). Can face images be intrinsically familiar? If so, can familiarity be measured consistently? We obtained three measures of familiarity for 100 hyper-realistic, GAN-generated faces, and examined the correspondence in responses among participants and among tasks. Our first task captured memorability (accurate recognition of something previously seen; recognition hit rate, Bainbridge et al., 2016) and familiarity (false recognition of something not previously seen; false alarm rate). However, false alarm-based quantification of familiarity alone is likely more conservative than our typical experiences of familiarity. Therefore, in a second task, we measured familiarity using an untimed forced-choice task in which a new group of participants chose the "more familiar" face in random pairs of faces. The resulting score for each face across participants serves as its familiarity score. Finally, in a third task, we aimed to capture the subjective nature of familiarity for individual faces by having a third group of participants rate faces on a sliding scale between "Not at all familiar" and "Extremely familiar". To establish the reliability among participants in their familiarity judgements, we computed Kendall ranked correlations between image rankings (by familiarity score) for 100 split-halves of the data for each task. We found widespread variability in image rankings (Exp.1 mean tau=0.07, Exp.2=0.01, Exp.3=0.04). We calculated the consistency of participant responses relative to population responses using logistic regression to predict familiarity scores and found varying levels of agreement by participant. Finally, we computed a Kendall correlation for image rankings between tasks and found no significant correlation. The lack of correspondence in responses among participants and tasks suggests that “familiarity” is likely not an intrinsic property of faces and that experimental measures may fail to capture our everyday experience of face familiarity consistently.