[Social psychological factors of interest in lay personality theories: why is ABO blood-typing popular?].

We hypothesized that one of the reasons that not a few Japanese are interested in lay personality theories of ABO blood-typing and similar unsupported beliefs on human nature, was unsatisfied needs of having clear collective and personal identities. To test the hypothesis, we asked 149 married women, 34 to 62 years of age, to describe themselves as in self introduction to strangers, and then separately indicate the degree of interest in lay personality theories. We then counted the number of references to personal/private aspects (an index of personal identity) and the number to social groups whose membership was known to be exclusive and limited (an index of collective one). Results showed that those who were high on both indices were less interested in lay theories than those low on one or both of personal and collective indices.