Professor of Psychology
Tokyo Woman's Christian University
"Only those with blood type AB were organized to launch a project which plans the development of and sales strategies for new facsimile machines," went part of an article introducing a decision by a noted electronics maker, in the November 21, 1990 issue of Asahi daily, one of Japan's large national newspapers. Perhaps those who are not Japanese found themselves baffled by what the article said. When asked "Do you think blood type reveals a man's personality, the majority of Japanese college students answer "Yes." This belief is not limited to college students alone. Corporate workers often bring up the topic of blood-type at the workplace. Believing, from his years of "experience," that there is a relationship between blood-type and personality, a personnel manager of the above mentioned electronics firm probably decided on the plan to exclusively utilize type AB persons to work on the product development and sales strategies.
In this paper, I would like to study from the perspective of social psychology the concept that blood- type has something to do with personality-which I call the blood-type theory of personality-. More specifically, I want to examine the appropriateness of this blood-type theory of personality, its significance in people's social life and the concomitant effects of the claimed relationship of blood- type and personality(Sato & Watanabe, 1992).
(2) Blood-typing Craze and Psychology
Psychologists have shown little interest in the issue of the relationship between blood-type and personality despite wider acceptance by many people of the notion that blood-type is related to personality. But a company, such as the one introduced in the opening part of this paper, utilized blood grouping as a management tool. A kinder-garten, meanwhile, has adopted the way it educates children, depending on which blood types they have. This new trend prompted several psychologists(e.g. Ohmura 1990) to recognize the need for a psychological study of problems concomitant with the blood-type theory of personality and to conduct empirical research from several different viewpoints.
The first of several related research currents is concerned with use of existing personality tests to check to see if blood-type really affects personality. Takuma and Matsui(1985), for example, utilized the Edwards Personal Preference Schedule(EPPS) to examine the relationship between personality and blood typing. Meanwhile, Hasegawa(1985) used the Yatabe-Guilford Personality Inventory to do the same. Naturally, neither of the two research groups found any statistically significant relationship between test scores and blood groups. To say the least, no relation seem to be observed between blood types and "personality" utilizing existing personality tests.
The second research current attempted to clarify how many persons believe in this notion and how "different" they consider personality to be depending on blood groups, aside from the actual relationship between the two. In the 1985 Takuma and Matsui survey conducted among 613 male and female college students, about 48 percent said blood types make personality "extremely different" or "considerably different." Ninety-six percent of 105 college coeds questioned in a 1986 Toyama survey answered blood types "have much to do with" or "have something to do with" personality. Only four percent declared there is no relationship at all between the two. The percentage varied by sex and age group, but a very large number of young persons, it is fair to say, have interest in the blood-type theory of personality.
What are the personality traits of people with each of the four major blood types, designated as A, B, AB and O, then, and what do those who believe in this theory, think about this? In a 1988 survey by Sakamoto, 219 female college students were asked to evaluate the personality of "typical group A" and "typical group B" persons on 20 pairs of abjectives. They observed those with type B blood to be characterized as "cheerful, whimsical, self-centered, optimistic, highly individualistic, broad-minded, extraverted, positive and sociable," while those with type A blood are "neurotic, prudent, cooperative, sensitive, serious, realistic and rational." Of the four major blood groups, group A and group B persons tend to be more clearly contrasted with each other in personality traits.
The third current of research is an attempt to clarifying why many people tend to be affected by seemingly groundless opinions. Belief in what is scientifically unfounded has in itself some "functionality." Takuma and Matsui both varified in their joint 1985 research that those who see blood types and personality as being related to each other are more strongly colored by the need for affiliation, the need for deference, cyclical tendency and social extraversion than those who think otherwise. What is more, it was found that blood typing was seen to be similar to horoscope and palm reading. From these findings, Takuma and Matsui concluded as follows. Supporting the blood-type theory of personality, first, are auxiliary functions for socializing in the sense of providing topics; second, it functions as a tool for predicting the destiny and behavior of the self and others in the same manner as the horoscope does; and third, it functions as an aid to relying on authority in order to avoid complex thinking and use of judgment.
Finally, much research has been carried out on why blood types and personality "seem" related to each other. In fact, when asked about the relationship between blood groups and personality, a vast number of people say, "That reminds me of something that I have forgotten until now." If so, then understanding why they believe there seems to be a relationship between the two should open the way for more in-depth and significant research. The first thing to note is the effect of "label." When they know their own blood types, or "labels," people have a strong tendency to consider the traits pointed out as being attributed to themselves. Ohmura(1984) clarifies the following fact. When reading a discription referring to the characteristics of personality which supposedly correspond to individual blood types, even though they are substituted for each other, the subjects often will detect the description referring to his or her own blood type and will reply "applicable to me." Hasegawa(1985) shows to the contrary. In short, when asked to evaluate a variety of personality characteristics, those who do not know their "labels" do not make systematically different replies depending on their actual blood types.
Let us now examine why people, when observing the behavior of others, tend to think of a description referring to the characteristics which were pointed out by the blood-type theory of personality as being applicable to themselves. This can generally be considered as a problem of why stereo-typed traits are maintained and reinforced. First, the following fact was determined by Snyder and Uranowitz(1978). When they receive information corresponding to the stereo-typed charcteristics, those with stereo-typed traits accept it as it appears to them and bear it in mind well. When they receive one which is contradictory to the stereo-typed traits, however, they either tend to reinterpret it in such a manner that it agrees with the stereo-typed traits or tend to forget it. This is also applicable to the stereo-typed blood groups. Take Sakamoto(1989), for instance. In his research, Sakamoto made the subjects read descriptions which refer to the characteristics of the "typical group A person" or the "typical group B person." Then, he had them read "diaries on a certain day by certain persons." Thereafter, he had them recollect what the diaries were about and found that those who read a description of the traits referring to the "typical group A person" remembered well the diary written by the type A person, while those who read a description of the traits referring to the "typical group B person" remembered well the one written by the type B person.
(3) Hazards of the Blood-Type Theory of Personality
The blood-type theory of personality, as long as it is used only as a tool for easy conversation, may not pose a serious problem. However, psychologists entertain some misgivings about it from the following two points of view.
First, the possibility is that belief in the relationship between blood-type and personality shared by many persons, even if it proves wrong, will come true. This is a process which is termed as the self-fulfilling prophecy. In this process, when a person develops an expectancy(prophecy) of others, he generally accepts the information which corresponds to his expectancy, but does not accept that which runs counter to it, thereby "seeing" reality as it was initially hoped for. Furthermore, he acts in the way his expectancy is to be met, which in turn leads others to behave in the same fashion, thus "actualizing" his own expectancy.
Referring to the blood-type theory of personality, if we believe, for example, that "group B persons are easygoing," then we gradually come to see them truly as such by the type of distorted recognition mentioned in the previous section. What is more, if we believe that others are optimistic, we will probably mix with them casually and will thus likely make them actually act like optimistic persons in these situations. This would mean that the existence of solidly stereo-typed persons will prompt a relationship to be actually created by blood-type and personality despite the fact that there is no such essential relationship between the two.
Sakamoto and Yamazaki(1991) conducted interesting research in this respect. They listed as characteristics associated with group A persons "prudent" and "able to draw a line" and as those associated with group B persons "not hung up on details" and "whimsical." Then they gave 1 point to those who answered "Applicable to me" and 0 point to those who replied "Not applicable to me" and found the total for each charactristic. Thus, the more points they got, the more strongly they are regarded as "group A persons," while the fewer points they got, the more strongly they are regarded as "group B persons." Analysis of biannual data from 1978 to 1988 showed that type A persons gradually got higher points for type A. Namely, no differences were observable at first between type A and type B persons in 1978, but those with type A blood alone tended to distinguish themselves from those having any other blood type as having a type A personality(Fig.1). This indicates that self-description of the subjects underwent changes, but it is not clear whether it also caused their behavior to change. It is fair to say, however, that it indicates a strong impact on the stereotypes of blood groups.
Second, a problem involving prejudice and discrimination must be cited. The percentage of the four major blood groups in Japan is as follows: 40 percent group A persons, 30 percent group O persons, 20 percent group B persons and 10 percent group AB persons. It has been found in past studies that many persons have a negative impression of those with type AB blood, the percentage of which is the smallest of the four. In the work of Sato, Miyazaki and Watanabe(1991), for example, a group of students were ask to freely describe their impressions of those with the four major blood groups. Then the other group of students was asked to evaluate how desirable those with the four blood groups are in terms of their respective characteristics obtained from the initial free description. The values obtained were summed for each blood type, and it was found that the subjects had bad impressions of type AB persons as compared with the other blood type persons. We can easily imagine that this kind of prejudice exerts a negative influence on interpersonal relations.
In the example given in the opening part of this paper, employees with type AB blood were picked out for a development project because of their "ability to make plans." But to the contrary, negative impressions of those with type AB blood, we cannot deny, will not possibly put them in a disadvantageous position in terms of personnel management. Personnel management, if implemented, by an uncontrollable factor of blood-type, would constitute nothing but discrimination. We may not be critical of bringing up blood grouping as a "lubricant" for coversation, but we need to bear in mind the fact that there lurks a structure which will breed prejudice and discrimination in talking about the relationship between blood-type and personality.
Finally, in this paper, I discussed the hazards involving stereo-typed interpretations of blood-type, and I want the reader not to have a stereo-typed belief that " the Japanese are people who are stupid enough to believe in the relationship between blood-type and personality." There are many Japanese who do not believe in such a relationships. In addition, the hazards resulting from the formation of stereotypes are not limited to those related to blood-type. The process in which stereotypes are created and are confirmed is found inside the mind per se of people who "try to know" the object. The attitudes toward checking the process in which a person forms his own judgment, it is safe to say, are necessary for all.
Hasegawa, H. 1985 There is no ground for believing the "blood-type theory of personality." Proceedings of the 27th annual meeting of Japanese association of educational psychology, 422-423.
Ohmura, M. 1990 Blood-type and personality. Fukumura-Shuppan.
Sakamoto, A. 1988 Selective perception by ABO blood-type stereotype. Proceedings of the 30th annual meeting of Japanese association of educational psychology, 604-605.
Sato, T., & Watanabe, Y. 1992 Psychological studies on blood-typing in Japan. Japanese Review of Psychology, 35, 234-368.
Sato, T., Miyazaki, S., & Watanabe, Y. 1991 A study on blood-type theory of personarity(3): From stereotype to prejudice. Proceedings of the 33rd annual meeting of Japanese association of social psychology, 342-345.
Snyder, M., & Uranowitz, S. W. 1978 Reconstructing the past: Some cognitive consequences of person perception. Journal of Personality and Social Psychology, 36, 941-950.
Takuma, T., & Matsui, Y. 1985 On blood-type stereotype Jinbun Gakuhou (Tokyo Metropolitan University), 145, 57-71.
Toyama, M. 1986 Effects of streotype in processing of information about other people. Bulletin of Aoyama-Gakuin University, 40, 129-148.
Yamazaki, K., & Sakamoto, A. 1992 Self-fulfilling prophecy through blood-type stereotyping. Proceedings of the 33rd annual meeting of Japanese association of social psychology, 342-345.
Sakamoto, A. 1989 Knowledge of blood-type streotypes and the distortion of memory. Proceedings of the 30th annual meeting of Japanese association of social psychology, 29-30.
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