大林 陽太

<jats:sec><jats:title>Introduction</jats:title><jats:p>Smiling during conversation occurs interactively between people and is known to build good interpersonal relationships. However, whether and how much the amount that an individual smiles is influenced by the other person’s smile has remained unclear. This study aimed to quantify the amount of two individuals’ smiles during conversations and investigate the dependency of one’s smile amount (i.e., intensity and frequency) on that of the other.</jats:p></jats:sec><jats:sec><jats:title>Method</jats:title><jats:p>Forty participants (20 females) engaged in three-minute face-to-face conversations as speakers with a listener (male or female), under three conditions, where the amount of smiling response by listeners was controlled as “less,” “moderate,” and “greater.” The amount of the smiles was quantified based on their facial movements through automated facial expression analysis.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>The results showed that the amount of smiling by the speaker changed significantly depending on the listener’s smile amount; when the listeners smiled to a greater extent, the speakers tended to smile more, especially when they were of the same gender (i.e., male–male and female–female pairs). Further analysis revealed that the smiling intensities of the two individuals changed in a temporally synchronized manner.</jats:p></jats:sec><jats:sec><jats:title>Discussion</jats:title><jats:p>These results provide quantitative evidence for the dependence of one’s smile on the other’s smile, and the differential effect between gender pairs.</jats:p></jats:sec>

Neural connectivity was measured during motor imagery (MI) and motor execution (ME) using magnetoencephalography in nine healthy subjects, MI, and at rest. Lower coherence values during ME and MI between sensorimotor areas than at rest, and lower values during MI between the left supplementary motor area and inferior frontal gyrus than ME suggested the sensorimotor network of MI functioned with similar connectivity to ME and that the inhibitory activity functioned continuously during MI, respectively.