This study assesses how people interpret human ages based on images of faces. We assigned the age of the people imagining how old they are as the 'subjective age' and proposed an experiment to identify its mechanism. The participants in the experiment were presented with the facial images of other people and asked to estimate the ages of those in the images as either younger or older than their own ages. Then, we calculated the difference between the subjective ages given by participants that matched their own ages and the actual ages of the people in the images. Results showed that subjective age was generally underestimated by Japanese, Korean, and American groups. The results also suggest that the factors of a younger identity include 1) the effect of delusions of the accumulated memory of self-image, and 2) sociopsychological parameters. To examine the effect of delusions of the accumulated memory of faces, we conducted the experiments of relative age comparison between well-known others' faces (own brothers/sisters) and unknown others' faces. The results confirmed that people tended to underestimate the ages of well-known others' faces compared with unknown faces. These results are consistent with our hypothesis that a younger identity is influenced by the effect of delusions of the accumulated memory of known faces.