a self-fulfilling prophecy. Cosy Muto and Masahiro Nagashima et al. (Nagasaki University) conducted a supplementary survey of Yamazaki and Sakamoto in 2011. They demonstrated that significant and the same difference in personalities between blood-types by using the same database as Samamoto and Yamazaki used. In the 1990s, the difference due to blood types was stabilized and variances became smaller. Then in the 2000s, the difference was statistically significant, too. However, the effect magnitude was extremely small, despite 'significance' in the statistical sense. Another Japanese social psychologist, Shigeyuki Yamaoka (Shotoku University), announced results of his questionnaires, which were conducted in 1999 (1,300 subjects) and 2006 (1,362 subjects), In both cases, the subjects were university students, and only subjects with enough knowledge of and belief in the "blood-type diagnosis" showed meaningful differences. He concluded that these differences must be the influence of mass media, especially TV programs. Yamaoka later examined 6,660 samples from 1999 through 2009 in total and found the same result. On the other hand, there are opinions that the statistically meaningful differences according to the blood types are not explained only by beliefs, nor are they a self-fulfilling prophecy. In Japan, the penetration rate of blood-typical personality traits was investigated. Yoriko Watanabe, a Japanese psychologist (then Hokkaido University), chose "well-known" traits and found most traits were known to no more than half of Japanese (subjects were university students). A Japanese writer, Masayuki Kanazawa, analyzed these blood-typical traits in combination with data from Yamaoka (1999) that used the same items of Watanabe's penetration survey. If blood-typical differences are caused by penetration (or their self-recognition), the rate of differences of a trait is proportional to the rate of its penetration. However, Kanazawa was not able to discover any association with blood-type differences and penetration rates. This result raises doubt about the role of beliefs and self-fulfilling prophecy. Most reports that demonstrated statistical correlation attribute differences to a self-fulfilling prophecy. However, no study directly proved the existence of "self-fulfillment". Therefore, the opinions of researchers are varied at present: Whether there is a statistical correlation or not; Whether any statistical correlations are superficial, being caused by subjects' self-fulfilling prophecy, or if they are truly caused by the blood type. In a 2021 Japanese study, ANOVA results of a 6,000-population large-scale survey showed that respondents displayed the personality traits corresponding to their own blood type more strongly than respondents who had different blood types