Pupil contagion is the phenomenon in which an observer’s pupil-diameter changes in response to another person’s pupil. Even chimpanzees and infants in early development stages show pupil contagion. This study investigated whether dynamic changes in pupil diameter would induce changes in infants’ pupil diameter. We also investigated pupil contagion in the context of different faces. We measured the pupil-diameter of 50 five- to six-month-old infants in response to changes in the pupil diameter of upright and inverted faces. The results showed (...) that in the upright presentation condition, dilating the pupil diameter induced a change in the infants’ pupil diameter while constricting the pupil diameter did not induce a change, and pupil contagion occurred only in the upright face presentation, and not in the inverted face presentation. These results indicate the face-inversion effect in infants’ pupil contagion. (shrink)

This study examined whether 8-month-old infants’ hemodynamic responses in the temporal region were modulated by repeated presentation of “Peekaboo” by using functional near-infrared spectroscopy. Previous studies have shown that infants’ temporal region responds to faces. A recent electroencephalography study showed that the neural activity of infants was modulated by repeated presentation of “Peekaboo.” Some fNIRS studies also revealed that the movie of “Peekaboo” activated the hemodynamic response of the temporal region in infancy. However, no studies have shown the hemodynamic modulation (...) of the temporal region according to the repeated presentation of “Peekaboo” in infants. In order to examine whether the hemodynamic responses of the temporal region were modulated by repeated presentation of “Peekaboo,” we compared the activity of the temporal region between the early and late trials. We set long and short delays before face-presentation. The results showed that the concentration of oxy-hemoglobin in the right occipitotemporal region in both conditions increased after the presentation of “Peekaboo” relative to the baseline. Moreover, in the long delay condition, the hemodynamic modulation of the right occipitotemporal region was induced according to the repeated presentation of “Peekaboo” in infants. (shrink)