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Identical twins’ failings at discriminating each other’s faces

Identical twins are no better than outsiders at recognizing photos of each other’s faces when the photographs are upside down, and sometimes when the photos are rightside-up, says this new study:

Is That Me or My Twin? Lack of Self-Face Recognition Advantage in Identical Twins,” Matteo Martini, Ilaria Bufalari, Maria Antonietta Stazi, Salvatore Maria Aglioti, PLoS ONE 10(4): e0120900. The authors, at the University of Rome “La Sapienza,” IRCCS Fondazione Santa Lucia, Rome, Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain, University of East London, UK, and the National Twin Registry—Italian National Institute of Health, Rome, Italy, report:

Despite the increasing interest in twin studies and the stunning amount of research on face recognition, the ability of adult identical twins to discriminate their own faces from those of their co-twins has been scarcely investigated…. Given the very high level of resemblance of their faces, monozygotic twins represent a unique model for exploring self-face processing….

We devised a task in which monozygotic twins were asked to report by pressing one of three keys whether upright and inverted facial pictures were of themselves or the co-twin. As a control, we also included a non-twin face to test whether twins were better at recognizing their co-twins’ face or another personally well-known face, which was matched as much as possible for familiarity, exposure, and emotional valence….

Twins lack self-face recognition advantage….

The more the twins felt as if they physically resemble each other, the lower their performance at identifying their own face. In other words, sharing highly similar physical features impaired twins’ ability to discriminate the self from the co-twin’s face….

The Twins were better in recognizing the self and co-twin faces with respect to control participants when stimuli were upright ((0.061 ± 0.013) vs. (0.041 ± 0.020); p = 0.002), but performed similarly when stimuli were inverted ((0.040 ± 0,012) vs. (0.033 ± 0.018); p = 0.294))

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