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Abstract

When two faces are displayed next to each other under similar viewing conditions, we can easily judge whether they represent the same person or not. However, little is known about how well our visual system can differentiate between two faces with increasing levels of similarity. Even less is known about whether differentiating between similar or different faces induces different gaze patterns. To measure the limits of face discrimination ability, we used pairs of morphed faces that were created with an equal number of ‘parent’ faces but never shared any parent faces. To manipulate similarity, we increased the number of parents; the larger the number of parents the more similar the test faces were. Participants remained over guessing rate even when test faces were created out of 32 parents faces each, demonstrating remarkable face discrimination ability. To investigate whether the increased similarity between test faces affects how we compare them, participants’ eye movements were tracked during the discrimination task. Increased face similarity elicits more gaze fixations overall. However, the gaze distribution pattern remained the same whether participants saw two highly similar or dissimilar faces. These results demonstrate that we use stable gaze strategies for discriminating two faces regardless of task difficulty.