Abstract
Whether or not self-face is processed more accurately than other-face has not been conclusively determined. In most studies, participants see self-face or other-face and must judge whether it is “self” or “other.” The accuracy in “self” and “other” trials are compared to discuss self-advantage. In this experimental procedure, however, participants could give a correct answer in “other” trials not by identifying “other” but rather by rejecting “self.” To compare “self” and “other” in an equal condition, we used an adapted ABX test procedure. We created a series of morphed faces which gradually deviated from the original face and tested the amount of morphing necessary for a participant to recognize the modification. If participants notice more slight modifications in self-face than in other-face, it suggests that the representation of self-face is more fine-tuned, which can be interpreted as self-advantage. Participants (n=16) were recruited in pairs with gender-matched familiar others. Photographs of “self” (participants), “familiar” (pair), and “other” (stranger) faces were morphed parametrically with another face from a database. In each trial, three faces were sequentially presented, one of which was a morphed face while the other two were the original stimulus. If the participants can detect modifications, they would select the morphed face as an odd stimulus; otherwise, the accuracy would be at a chance level. The morphing percentage or the threshold at which the accuracy exceeds a chance level was measured by a 1-up 1-down staircase procedure. Results showed that the thresholds in “self,” “familiar,” and “other” conditions were morph 83% (original 83% + another face 17%), 82%, and 74% respectively, indicating that the participants were more sensitive to changes in self and familiar faces than strangers’ faces (t(22.9)=3.2, p=.004; t(20.8)=3.1, p=.006). We will also present the results obtained with voice stimuli and further discuss differences and similarities across modalities.