Abstract-We have proposed a method for estimating the subjective age of a person; that is, a method that yields a person's age on the basis of estimations made by that person about the age of other people by observing their facial images. Thus far, experiments have shown that Japanese people tend to underestimate their subjective age. In this study, we focus on the socio-psychological effects that may influence the underestimation of subjective age. We conducted an international comparative study. In this study, experiments were performed in which American and Japanese participants viewed American facial images; in addition, the American participants also viewed Japanese facial images. Through these experiments, it was confirmed that the subjective age generally tended toward the negative direction despite differences in the nationalities and cultures of the Japanese and American participants and their facial images. Moreover, it was found that nationality and culture may have some effects on the estimation; for example, American males did not exhibit the tendency to underestimate the age, unlike Japanese male. When estimating facial images of different nationalities, the variance generally tended to be larger, although the average was similar. This study suggests that the underestimation of age occurs despite differences in Japanese and American societies and cultures; however, the tendency of underestimation of age is not related to facial images but to social and cultural factors that influence the participants.

We have defined the perception of one's own age as "subjective age", and have so far approached using other people's facial images. In this paper, we propose a relative estimation method for subjective age by using people's speech sounds and their chronological age. A relative estimation task is performed, wherein an estimator gives rating values to other people about whether they are older or younger than the estimator. In this task, the difference in the actual age between the estimator and the rating value of the person are measured. We plot the results on a two-dimensional plane with the x-axis as the relative age and the y-axis is the estimation result. Thus, the distribution with the plotted points of upper-right direction is obtained, which is approximated by a logistic function. The zero crossing point in the approximation curve with the x-axis is defined as the shift value in the subjective age. 57 total estimators, including 28 males and 29 females from 25 to 44 years old participated in this experiment. As a result, the subjective age using speech sounds tended to be older than using facial images. The tendency was also more remarkably visible in the male groups than in the female group. However, variance was relatively higher in the male young-middle (35-44) and the female young (25-34) groups than using facial images, which indicated that the subjective age varies according to the profile of estimators, such as age and gender.