ABSTRACT: Context: The theory that there is a possible correlation between blood types and personality characteristics has been floating for a long time. Though there have been many attempts to evaluate this theory, the results have been inconsistent and can be best described as conflicting. Aim: The aim of our study was to explore a possible correlation between blood groups and certain specific personality traits, in a large sample of medical students in south India.Setting: The study was conducted at Karpaga Vinayaga Institute of Medical Sciences, Maduranthagam, India, in November-December, 2012.Participants: Our study included 502 medical students of the age group 18 – 22 years.Methods: ABO blood typing was done using the Agglutination method. For assessment of personality traits, we used one of the most researched, reliable and validated personality assessment tools, namely the Eysenk Personality Questionnaire – Revised (EPQ-R). EPQ-R assesses the three major personality dimensions: P (Psychoticism or “Tough Mindedness”), N (Neuroticism or “Emotionality”) and E (Extraversion or “Sociability”). Analysis of data was done using SPSS software (version 15). MANOVA and Tukey’s HSD were the statistical tests used to determine statistical significance. Results and Conclusion: Our study revealed a significant difference in ‘Extraversion’ scores between the blood groups B and AB. However, when the analysis was done separately for males and females, there was no significant correlation between blood types and personality traits. This implies gender was probably a confounding factor responsible for the initial difference in ‘Extraversion’ scores. So, the conclusion of our study was that there was no real correlation between blood groups and personality traits.

INTRODUCTION:

Ancient theories of personality linked personality types to body fluids. Hippocrates and Galen were among the first to postulate a biological basis for personality. According to them, different temperaments or personality types were associated with four basic body fluids or ‘humors’.  The theory that there is a correlation between blood types and personality characteristics has also been in existence for a long time. In some countries, especially Japan, there was widespread belief that blood type is strongly linked to personality and interestingly, many Japanese corporations have used blood type as the basis for marketing, management, and other business practices.

In terms of empirical research, though there have been many studies which have attempted to evaluate this theory, the results of these studies can be best described as conflicting. Also, the interpretation of their results had been problematic. This was due to a variety of reasons – loosely defined aims, non-homogenous population, variable assessment tools and other methodological issues.

As early as 1927, Furukawa proposed that there is a definitive correlation between blood types and personality characteristics1. A few years later, Thomson (1936) criticized Furakawa’s study, quoting methodological and statistical flaws and concluded that there is no relationship between blood type and personality2.

In the later years, researchers developed more objective and structured assessment tools to measure personality characteristics like the Eysenck Personality Inventory (Eysenck & Eysenck, 1964)3, the Sixteen Personality Factors Inventory (Cattell, Eber & Tatsuoka, 1970)4 and so on.  Subsequently, there were a number of studies which attempted to study the relationship between personality characteristics and blood types, using structured assessment tools. However, the results of these studies varied widely. Angst & Maurer-Groeli (1974) found higher Neuroticism scores among persons with blood type B and higher Introversion scores among persons with blood type AB5. Cattell et al (1980) used the 16 PF to assess personality characteristics, in a sample of Australian residents and found some significant relationships between blood type and personality6. Rinieris et al (1980) found no significant correlation when using the EPQ or Maudsley Personality scores in a large sample of Greek respondents7. Eysenck classified countries based on personality scores and reported that countries with low scores on Extraversion had a higher percentage of people with blood type AB and countries with higher scores on Neuroticism had a higher percentage of blood type B8. Lester & Gato (1987) found higher Extraversion scores among persons with type O and AB than those with types A and B9. However, two Indian studies by Marutham & Prakash (1990)10 and Gupta (1990)11 reported that there were no significant differences in Extraversion scores among any of the blood types. Both these studies rather observed that Neuroticism scores were higher among participants with Type B. Rogers & Glendon (2003) using a version of the big five factor personality inventory, concluded that their study did not support any significant relationship between blood type and personality12.

 

METHODS:

 

STUDY DESIGN: A cross-sectional study design was used

 

Participants:

Inclusion criteria: Medical, Dental and Nursing students with age between 18 and 22 years.

A total of 502 medical professional students, with 335 females and 167 males, who fulfilled the inclusion criteria, were included in the study.

Setting: The study was conducted at Karpaga Vinayaga Institute of Medical Sciences, Maduranthagam in November-December, 2012.

Blood typing: Blood samples were taken by finger pricks from the students and the open slide method of ABO blood groups testing was followed. RBCs suspended in isotonic saline were treated with anti-A, anti-B and anti-D antisera (Span Diagnostics, Gujarat) on glass slides and mixed with separate applicator sticks. The mixture was observed for agglutination with corresponding antisera and compared with the control for confirmation.

Personality assessment tool:

Personality traits was assessed using Eysenck Personality Questionnaire-Revised (EPQ-R).

EPQ-R is an objective tool for the assessment of personality, and is one of the oldest and most validated tools used in psychological research. EPQ-R reliably measures three major dimensions of personality that account for most of the variance in personality.  EPQ-R is a self-report questionnaire and comprises of 100 easily understandable “Yes/No” questions.

The three major personality dimensions or factors assessed in EPQ-R are: P (Psychoticism or “Tough Mindedness”) – 32 items, N (Neuroticism or “Emotionality”) – 24 items, E (Extraversion or “Sociability”) – 23 items. There is a fourth measure called a “Lie scale” – 21 items, which is aimed at detecting inaccuracies due to dishonest responses.

Implications of EPQ-R scores:

Individuals with high scores on the “Psychoticism” scale are likely to be tough-minded, aggressive, cruel, inhumane, intolerant, manipulative and egocentric. They display tendencies to develop psychotic disorders.

Individuals with high scores on the “Neuroticism” scale are likely to be nervous, emotional unstable, and tend to have high levels of anxiety / depression. They are more prone to develop neurotic or stress-related disorders.

Individuals with high scores on the “Extraversion” scale are likely to be sociable, outgoing and uninhibited.

DATA COLLECTION:

The student were administered the EPQ-R questionnaires, after getting their informed consent, and with instructions that their data would be kept confidential.

 

DATA ANALYSIS:

Out of the 502 students (335 girls and 167 boys) who were administered the questionnaire, 496 (332 girls and 164 boys) completed and returned the questionnaires. Out of these, the EPQ-R questionnaires which had a Lie scale score of >50% were excluded from the analysis in order to improve the validity. The remaining valid questionnaires, which were considered for analysis, were categorized based on gender and blood types.  Among the females, 54 had blood type A, 69 had blood type B, 78 had blood type O and 17 had blood type AB. Among the males, 30 had blood type A, 43 had blood type B, and 42 had blood type O and 18 from group AB.

MANOVA and Tukey’s HSD were the statistical tests used to compare the blood type (A, B, O and AB) means for the three scales of EPQ-R, namely Psychoticism, Neuroticism and Extraversion. SPSS software (version 15) was used to compute the statistical calculations.

RESULTS:

The results of our study are tabulated below. Table 1 shows that the mean age of participants was 19.25 yrs (19.52 yrs. for females and 19.09 yrs. for males). The sex distribution (represented in Figure 1) was 62.11 % females and 37.89 % males.

Table 2 shows the overall association between blood groups and personality traits.  Our study revealed that there was a significant difference in the “E (Extraversion)” scores between the blood groups B and AB.

We also evaluated the association between blood groups and personality traits among females and males separately (shown in Table 3 and 4 respectively). The results of this showed that there was no significant association between blood groups and personality traits.

 

 

Table 1: Mean age of participants

  N Min. age (yrs.) Max. age (yrs,) Mean age (yrs.) S.D.
Total 351 18 22 19.25 1.113
Female 218 18 22 19.09 1.068
Male 133 18 22 19.52 1.139

 

 

 

Figure 1: Sex distribution among participants

 

Table 2: Overall association between blood groups and personality traits

Personality trait Blood group Significance (p)
P A B

AB

O

0.551

0.972

0.996

B A

AB

O

0.551

0.477

0.623

AB A

B

O

0.972

0.477

0.924

O A

B

AB

0.996

0.623

0.924

E A B

AB

O

0.935

0.125

0.987

B A

AB

O

0.935

0.034 *

0.992

AB A

B

O

0.125

0.034 *

0.053

O A

B

AB

0.987

0.992

0.053

N A B

AB

O

0.973

0.539

0.924

B A

AB

O

0.973

0.319

0.660

AB A

B

O

0.539

0.319

0.783

O A

B

AB

0.924

0.660

0.783

P = Psychoticism, E = Extraversion, N = Neuroticism, *Significant (p < 0.05)

Table 3: Association between blood groups and personality traits among females

 

Personality trait

Blood group

No. of participants

Mean (S.D.)

95% C.I.

Significance      (p)

Lower bound

Upper bound

 

 

P %

A

B

AB

O

Total

54

69

17

78

218

28.41 (10.79)

28.98 (11.00)

25.55 (7.98)

27.84 (11.19)

28.17 (10.79)

25.46

26.34

21.44

25.32

26.72

31.36

31.63

29.65

30.37

29.61

0.686

 

 

E %

A

B

AB

O

Total

54

69

17

78

218

63.52 (15.09)

63.83 (17.31)

72.63 (9.32)

63.88 (18.31)

64.45 (16.75)

59.40

59.67

67.84

59.75

62.22

67.64

67.99

77.42

68.01

66.69

0.222

 

 

N %

A

B

AB

O

Total

54

69

17

78

218

60.18 (17.44)

58.57 (21.31)

67.64 (19.34)

63.62 (19.95)

61.48 (19.83)

55.42

53.45

57.69

59.12

58.83

64.94

63.69

77.59

68.11

64.13

0.235

P = Psychoticism, E = Extraversion, N = Neuroticism

 

 

 

 

 

 

 

 

 

 Table 4: Association between blood groups and personality traits among males

 

Personality trait Blood group N Mean (S.D.) 95% C.I.

Significance (p)

Lower bound Upper bound
P % A

B

AB

O

Total

30

43

18

42

133

33.33 (14.59)

38.08 (13.53)

32.46 (12.91)

35.59 (14.60)

35.46 (14.04)

27.88

33.91

26.04

31.04

33.05

38.78

42.25

38.88

40.14

37.87

 

 

 

 

0.394

E % A

B

AB

O

Total

30

43

18

42

133

64.34 (19.52)

60.06 (17.98)

70.04 (12.37)

61.38 (16.83)

62.79 (17.46)

57.05

54.52

63.89

56.14

59.80

71.63

65.59

76.20

66.63

65.79

 

 

 

 

0.198

N % A

B

AB

O

Total

30

43

18

42

133

57.08 (22.45)

56.68 (20.53)

61.34 (17.49)

55.65 (18.14)

57.08 (19.74)

48.69

50.36

52.64

49.99

53.69

65.46

63.00

70.04

61.30

60.46

 

 

 

 

0.787

P = Psychoticism, E = Extraversion, N = Neuroticism

 

DISCUSSION:

The strengths of our study include a clearly defined aim, a large sample size, a homogenous sample population, a scientific method of determining blood groups (in contrast, self-reported measures were used in some of the previous studies), a valid and reliable method of assessment of personality traits and a high response rate for the personality assessment questionnaire (98.80 %).

Though our study showed that there was a significant difference in the ‘Extraversion’ scores between the blood groups B and AB, when the analysis was done separately for males and females, there was no significant association found between any blood group and personality traits. It is indeed a well known fact that significant personality differences exist between males and females and hence gender was probably a confounding factor responsible for the initial difference in the Extraversion scores. So, the conclusion of our study was that there was no real correlation between blood groups and personality traits. The present study confirms the views of Rinieris et al (1980) and Rogers & Glendon (2003), but contradicts the findings of several researchers such as Angst & Maurer-Groeli (1974), Lester & Gato (1987), Jogawar (1984), Marutham & Prakash (1990), Gupta (1990) and Macaskill et al (1994).

There are a few limitations to the study. One was unequal cell sizes among the different blood groups, with a low number of participants with blood type AB. Secondly, though there was a high response rate (98.80 %), only 351 out of the 496 completed questionnaires (70.76 %) could be included in the study since the rest had to be eliminated due to Lie scale scores of  > 50%. The other issue was that we evaluated only the three major personality traits, namely Psychoticism, Extraversion and Neuroticism. Since ‘Personality’ is a very broad construct, it is possible that there could be many other personality characteristics which could vary on the basis of blood types.

It is well established that blood types are predominantly genetically determined and similarly, it is also known that personality characteristics have significant genetic basis. This, in fact, is one of the main reasons why several attempts have been made, trying to unravel a possible (genetic) correlation between these two. One reason why many studies, including ours, have failed to establish this correlation and many others have yielded conflicting results, could be due to the fact that the genetic basis of personality could be much more complex than imagined. Unlike blood types, which are predominantly single gene-mediated, the genetic determinants of personality could be multi-gene related and locating these determinants based on single gene-based factors such as blood types is difficult.

 

REFERENCES:

  1. Furukawa, T. (1927). A study of temperament by means of human blood groups. Japanese Journal of Psychology, 2, 612–634.

 

  1. Thompson, G. N. (1936). Blood type as related to intelligence, emotions, and personality. Journal of Applied Psychology, 20, 785–789.

 

  1. Eysenck, H. J., & Eysenck, S. B. G. (1964). Manual of the Eysenck Personality Inventory. London: University Press.

 

  1. Cattell R.B., Eberand H.W. & Tatsuoka M. (1970). Handbook for the Sixteen Personality Factor Questionnaire. Champaign, IL: Institute of Personal Ability Testing.

 

  1. Angst, J., & Maurer-Groeli, Y. (1974). Blood groups and personality. Archiv fur Psychiatric and Nervenkrankbeiten, 218, 291–300.

 

  1. Cattell, R. B., Brackenridge, C. J., Case, J., Propert, D. N., & Sheehy, A. J. (1980). The relation of blood types to primary and secondary personality traits. The Mankind Quarterly, 21, 35–51.

 

  1. Rinieris, P. M., Christoloudous, G. N., & Stefanis, C. N. (1980). Neuroticism and ABO blood types. Acta Psychiatrica Scandanavica, 61, 473–476.

 

  1. Eysenck, H. J. (1982). The biological basis of cross-cultural differences in personality: Blood group antigens. Psychological Reports, 51, 531–540.

 

  1. Lester, D., & Gatto, J. (1987). Personality and blood group. Personality and Individual Differences, 8, 267.

 

  1. Marutham P. & Prakash I.J. (1990). A study of the possible relationship of blood types to certain personality variables. Indian Journal of Clinical Psychology 17 (1990), pp. 79-81.

 

  1. Gupta, S. (1990). Blood groups and personality characteristics. Personality and Individual Differences, 3, 317–318.

 

  1. Rogers, M., & Glendon, A. I. (2003). Blood type and personality. Personality and Individual Differences, 34, 1099–1112.

 

  1. Cramer, K. M., & Imaike, E. (2002). Personality, blood type, and the five-factor model. Personality and Individual Differences, 32, 621–626.

 

  1. Jogawar, V. V. (1984). Personality correlates of human blood groups. Indian Journal of Clinical Psychology, 11, 5–8.

 

  1. Cattell, R. B., Boutourline, H. Y., & Hundleby, J. D. (1964). Blood groups and personality traits. American Journal of Human Genetics, 16, 397–402.

 

  1. Ahmadi  E., Malekierad A. A., Maghsoudi M., Abdolmohamadi  K. & Fathi A. (2013). The relationship between Iranian undergraduate learners’ blood type and their personality. Language in India, 13:2, 218-226.

 

  1. Wu K., Lindsted K. D., Lee J. W. Blood type and the five factors of personality in Asia. Personality and Individual Differences, 38:4, 797-808.

 

  1. Macaskill G. T., Hopper J. L., White V. & Hill D. J. (1994). Genetic and environmental variation in Eysenck personality questionnaire scales measured on Australian adolescent twins. Behaviour Genetics, 24:6, 481-491.

Acknowledgements:

1)      We would like to thank Dr. R. Annamalai, Managing-Director, Karpaga vinayaga Institute of Medical Sciences for supporting us in this study.

2)      We would also like to acknowledge Mr. Porchelvan and Mrs. S. Valarmathi for helping us with the statistical work.

 

Conflict of Interest: None

 

Corresponding author:

Dr. M. Somasundaram,

Professor and Head of Department,

Dept. of Physiology,

Karpaga Vinayaga Institute of Medical Sciences,

Maduranthagam,

Kanchipuram District – 603308.

Email: drmssundar@yahoo.co.in

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