Conclusion
We demonstrated a clear relationship between blood type and the
self-reported personality of many single question items, which matches
traits previously stated. The effect of blood type on personality was
shown as partial η2 = 0.053 at the maximum in
this study ‒ the effect size was medium. The same traits were observed
in the two no-knowledge groups, though the difference was smaller.
People with no-knowledge of blood type traits might be less concerned or
sensitive to personality. A person without blood type knowledge had
lower scores of sociability and empathy, while those with more knowledge
had higher. If no-knowledge group has low sensitivity of the
personality, thereby the difference becomes small. This idea corresponds
with the actual data.
Blood type does not uniquely affect a person’s personality. On the
contrary, various factors such as gender and age have an intricate and
significant impact. This makes it impossible to achieve consistent
results without taking these non-linear interactions into account.
Traditional personality tests, such as the Big Five test, typically use
a personality factor that consists of multiple items. In this case, the
effect of blood type fluctuates, which can produce inconsistent results
unless the gender, age, or other conditions of the sample are properly
controlled. The explanation above is in good agreement with the theory
of personality psychology. Our findings provide a new, if hypothetical,
framework of how genes affect human personality.
Meanwhile, the sample in this study was limited to Japanese populations
only, the AI training data was small in sample size, its use was
experimental, and the interaction between gender and age is still
unknown. Additional research using larger, global dataset is needed in
order to address true implications as well as to improve algorithms and
methodologies.