Blood type and the five factors of personality in Asia

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Personality and Individual Differences 38 (2005) 797–808

Blood type and the five factors of personality in Asia

Kunher Wu a,*, Kristian D. Lindsted b, Jerry W. Lee c

a School of Public Health, Loma Linda University, Anderson Street, Loma Linda, CA 92350, USAb Department of Epidemiology, School of Public Health, Loma Linda University, Anderson Street,

Loma Linda, CA 92350, USAc Department of Health Promotion and Education, School of Public Health, Loma Linda University, Anderson Street,

Loma Linda, CA 92350, USA

Received 10 November 2003; received in revised form 19 April 2004; accepted 8 June 2004

Available online 10 August 2004

Abstract

Research investigating the association of blood type with personality has yielded mixed results. Tworecent studies (Cramer & Imaike, 2002; Rogers & Glendon, 2003) used inventories based on the widely

accepted five-factor model and found no significant relationship between blood type and personality.

Our study is the third published article to examine this relationship using the five-factor model. We ana-

lyzed 2681 Taiwanese high school students who completed the Chinese version of NEO-PI-R (Costa &

McCrae, 1992a) and reported their blood type. An ABO blood group test was performed on a sub-sample

of 176 students in the pilot study to assess the accuracy of blood type recall. Multiple linear regression anal-

ysis showed no significant relationship between blood type and personality except for Type AB females who

scored lower on the Conscientiousness domain. MANOVA results showed that the combined dependentvariables were not significantly affected by blood type or its interaction. We concluded that the potential

effect seen in Type AB females on Conscientiousness might be a chance finding because of the small sample

size (78). Academic achievement was positively related to Openness and negatively related to Extraversion.

However, BMI was inversely related to Extraversion in females.

� 2004 Elsevier Ltd. All rights reserved.

0191-8869/$ - see front matter � 2004 Elsevier Ltd. All rights reserved.

doi:10.1016/j.paid.2004.06.004

* Corresponding author. Address: 724 S. Garfield Avenue, Monterey Park, CA 91754, USA. Tel.: +1 626 975 9304;

fax: +1 626 288 7399.

E-mail address: [email protected] (K. Wu).

mailto:[email protected]

798 K. Wu et al. / Personality and Individual Differences 38 (2005) 797–808

Keywords: Blood type; Personality; Five-factor model; Asia; Neuroticism; Extraversion; Openness; Agreeableness;

Conscientiousness

1. Introduction

It is now widely accepted by scientists that genes determine our physical features, such as heightor hair color. However, there is not complete agreement regarding whether genes determine per-sonality traits (Steen, 1996). Studies have shown that approximately 40% of the variation in per-sonality can be explained by genes (Costa & McCrae, 1992b; Jang, Livesley, & Vernon, 1996).Because of complex interactions, classifying which genes are involved or the extent of theirinvolvement in determining a human trait is difficult. However, blood type is genetically predeter-mined and can be easily identified, so it has been used as a biological marker to assess the influ-ence of genetic factors on personality in Australia (Rogers & Glendon, 2003), Canada (Cramer &Imaike, 2002), Greece (Rinieris, Christodoulou, & Stefanis, 1980), India (Gupta, 1990; Jogawar,1983; Marutham & Prakash, 1990), Italy (Cattell, Boutourline, & Hundleby, 1964), Japan(Furukawa, 1930), and the United States (Lester & Gatto, 1987).

In 1930, Furukawa observed that participants with certain temperamental characteristicsseemed to have a specific blood type, and then concluded that temperament and blood type werecorrelated. In contrast, Thompson (1936) found no relationship between blood type and person-ality. In the 1960s and 1970s, researchers developed more sophisticated instruments to assess per-sonality traits, such as the Eysenck Personality Inventory (Eysenck & Eysenck, 1964), and theSixteen Personality Factors Inventory (Cattell, Eber, & Tatsuoka, 1970). Since then, psychologistshave studied Neuroticism and Extraversion extensively in relation to blood types. Angst andMaurer-Groeli (1974) found higher Neuroticism scores among persons with Type B. Jogawar(1983) found that people with Type B blood were less emotionally stable, more apprehensive,and less self-sufficient. Gupta (1990) observed that Neuroticism scores were significantly higherfor participants with Type B blood. Similarly, Marutham and Prakash (1990) reported that TypeB scored significantly higher on Neuroticism than other groups did. To determine the associationbetween blood type and national differences in personality, Eysenck (1982) reviewed studies inover 20 countries and suggested that the level of neuroticism in a country seemed to vary consist-ently with the proportion of persons in that country who had Type B blood. (He also suggestedthat Type AB was related to Psychoticism.) While these studies suggested that Type B blood wasrelated to Neuroticism, Cattell et al. (1964) and Rinieris et al. (1980) found no relationship be-tween blood type and Neuroticism.

The findings on Extraversion were less consistent. Lester and Gatto (1987) reported that indi-viduals with Type O or AB had significantly higher Extraversion scores than those with Type A orType B did. Angst and Maurer-Groeli (1974) reported that introversion was significantly morefrequent among people with Type AB. Individuals with Type AB were less extraverted than thosehaving Type A or Type O were, according to Gupta (1990). Marutham and Prakash (1990) re-ported no significant difference on Extraversion scores among A, B or O blood types. Cattellet al. (1964) reported no significant difference in Extraversion among the blood groups, but sug-gested that Type A were more tender-minded than individuals with other blood types were.

K. Wu et al. / Personality and Individual Differences 38 (2005) 797–808 799

In the past two decades, psychologists have agreed on the dimensions of adult personality traitsas explained by the five-factor model (Digman, 1990; Goldberg, 1990; John, 1990). Recently, Cra-mer and Imaike (2002) and Rogers and Glendon (2003) investigated the relationship betweenblood type and personality using measures based on the five-factor model. Neither study showedany significant relationship between blood type and the five factors of personality.

Our study is the first published article to examine the relationship between blood type and per-sonality based on the five-factor model in Asia, where the belief that blood type determines per-sonality is widely accepted. According to D�Adamo and Whitney (2001), more than 70% ofJapanese believe that blood type is directly related to personality. In Taiwan, books discussingthe influence of blood type on temperament and interpersonal relationships are readily available(Chang, 1999; Cheng, 1999; Lin, 1999).

Based on the literature and the popular beliefs in Asia, the following hypotheses were proposed:

1. Blood Type B individuals will score higher on Neuroticism than will other blood types.2. Blood Type O individuals will score higher on Extraversion than will other blood types.3. Blood Type A individuals will score higher on Agreeableness than will other blood types.4. Blood Type AB individuals will score lower on the Extraversion, Conscientiousness, and

Agreeableness than will other blood types.

Because people who believe that blood type determines personality may modify their behavior,we controlled for the effect of this belief in our analysis as well as for BMI and academic achieve-ment. Researchers have reported that women were more concerned about or dissatisfied with theirweight than men were (Furnham & Calnan, 1998; Furnham, Badmin, & Sneade, 2002) and thatbeing overweight hinders social interaction (Parızkova & Hills, 2001). However, other studiesfound no relationship between BMI and personality (Davis & Cowles, 1989; Wade, Loyden, Ren-ninger, & Tobey, 2003). It has been well documented that intelligence is a strong predictor of aca-demic achievement (Busato, Prins, Elshout, & Hamaker, 2000), and that academic achievement isrelated to personality (De Fruyt & Mervielde, 1996; Farsides & Woodfield, 2003). Studies of iden-tical twins reared apart suggest that genetics contributes to both BMI (Stunkard, Harris, Pedersen,& McClearn, 1990) and intelligence (Neisser, Boodoo, & Bouchard, 1996). Because genetic inter-actions are so complex, it may be that the genes which determine blood type are also associatedwith BMI and intelligence. To minimize potential cultural differences that may affect personality,we also controlled for the language spoken at home.

2. Methods

2.1. Overview

This study was divided into two parts: a pilot project and the main study. After giving in-formed consent, the participants were asked to indicate their blood type (A, B, O, or AB),and then complete the 240-item Chinese NEO-PI-R. We also performed an ABO blood grouptest (Sussman, 1968) on each participant in the pilot study to assess the accuracy of blood typerecall.


2.2. Participants

After obtaining permission from the city of Kaohsiung in March 2000 to conduct surveys in allof their 29 high schools, we used stratified random sampling to select participating classes fromeach school. We initially contacted 3844 11th grade students. We recruited students from the11th grade because, unlike seniors, they would not be studying for the college entrance exam,and would still meet the age requirement for administering the NEO-PI-R questionnaire (age16 years or older). Nearly 90% of potential participants (N = 3444) returned signed consent formsand were given the questionnaire. Forty-eight participants were excluded from our analysis be-cause they had more than 40 items missing, and for those who had less than 40 items missing,the missing data were replaced with the neutral response following the recommendations of Costaand McCrae (1992a). Of the 3396 participants, only those who reported their blood type wereanalyzed. Thus, the actual sample size was 2681 (45% males), with a sub-sample of 176 students(59% male) used for the pilot study.

2.3. Measures

The revised NEO Personality Inventory was developed by Costa and McCrae (1992a) througha factor-analytic approach to operationalize the five-factor model. It consists of 240 items withresponses given on a 5-point Likert scale to measure the five personality domains: Neuroticism,Extraversion, Openness, Agreeableness, and Conscientiousness. To allow a more comprehensiveassessment, each domain is defined by six facet scales with eight items each. Research on theNEO-PI-R in the US has demonstrated both reliability and validity (Costa & McCrae, 1992a).

In our previous paper (Wu, Lindsted, Lee, & Torres, in preparation), we have shown that theChinese version of the NEO PI-R used in this study was reliable. Internal consistencies for the fiveglobal domain scales were 0.91, 0.88, 0.79, 0.83, and 0.90 for N, E, O, A, and C, respectively. Prin-cipal components analysis with varimax rotation extracted five factors with loadings on the facetsthat were similar to the pattern found in the American normative sample (Costa & McCrae,1992a).

2.4. Multiple linear regression analysis

To investigate the relationship between personality and blood type, we analyzed a series of gen-der-specific, multiple linear regressions using self-reported blood types (A, B, O, or AB) with TypeO as a reference, controlling for academic achievement, body mass index (BMI), books, belief,and language. Cases with missing values in any of the variables used in a model were excludedfrom analysis. To check for assumptions, we followed the regression diagnostics outlined byKleinbaum, Kupper, Muller, and Nizam (1998) using graphical analysis of residuals. We exam-ined the condition indices and tolerance values to assess the collinearities between the independentvariables.

Books linking blood type and personality have been popular in Asia for decades. In order todetermine the extent of their influence, we asked two questions: ‘‘Have you read any books aboutblood type and personality?’’ and ‘‘Do you believe there is a relationship between blood type and per-

sonality?’’ The answers were dichotomous (yes or no); thus, one dummy variable was created for


each question. Since high school admission was based solely on national test scores, enrollmentwas used to measure academic achievement. Based on the Kaohsiung education department�sclassification of their 29 high schools, academic achievement was categorized as high, average,or low, with low as the reference. BMI, which was continuous, was calculated from self-reportsof height and weight using the equation weight (kg)/height2 (m). Because language is related toculture, students were asked whether they usually spoke Mandarin, Taiwanese, or the Hakka dia-lect at home. Because only 49 participants reported speaking Hakka at home, they were classifiedas having missing data on the language question. Thus, one dummy variable was created usingTaiwanese as the reference.

The continuous outcome variables were the five domains of personality: Neuroticism, Extraver-sion, Openness, Agreeableness, and Conscientiousness. The initial full model for each outcomevariable contained blood type, academic achievement, BMI, books, belief, and language as wellas the interaction terms between blood type and each of the independent variables. To reducethe model, a set of chunk tests using SPSS was performed to eliminate insignificant interactionsfrom the full model (Kleinbaum, 1994). The final regression model included all the potential con-founders along with the significant interaction terms (P < 0.05).

2.5. MANOVA

Since the NEO personality scales are related, a 2 · 4 (gender, blood type) multivariate analysisof variance (MANOVA) was performed using SPSS on the five continuous dependent variables:Neuroticism, Extraversion, Openness, Agreeableness, and Conscientiousness. Nominal independ-ent variables were gender and blood type (A, B, O, AB). To check for the equivalence of covar-iance matrices across the groups in MANOVA, Levene�s test of equality of error variances wasperformed for all variables (Hair, Anderson, Tatham, & Black, 1998). Since there is no standardtest for multivariate normality, each dependent variable was tested for normality.

3. Results

3.1. Population

We conducted a pilot study of 176 Taiwanese students to assess the accuracy of self-reportedblood types. Out of the 126 students (71.6%) who reported their blood type, 116 (92%) were cor-rect. The accuracy was similar across blood types. In the US, Lester and Gatto (1987) have re-ported 44.6% of the students stated they knew their blood type, and of these 85.5% werecorrect. Table 1 shows the distribution of demographic variables separated by academic achieve-ment. Out of 3396 students, 715 did not know their blood type. Of the 2681 self-reported bloodtypes, there were 651 with Type A (24.3%), 610 with Type B (22.8%), 1282 with Type O (47.8%),and 138 with Type AB (5.1%). Mourant, Kopec, and Domaniewska-Sobezak (1976) have re-ported similar results in the Chinese population: Type A (27.0%), Type B (23.3%), Type O(43.9%), and Type AB (5.8%).

Three-fourths (75.4%) of those who responded to the question, ‘‘Have you read any books about

blood type and personality?’’ answered yes. More than half (65.7%) of those who responded to the

Table 1

Distribution of gender, blood type, books, belief, and language separated by academic achievement level

Academic achievementa Total

High Average Low

Males 386 (26%) 716 (48%) 395 (26%) 1497

Females 344 (18%) 733 (39%) 822 (43%) 1899

Type A 144 (22%) 275 (42%) 232 (36%) 651

Type B 146 (24%) 252 (41%) 212 (35%) 610

Type O 307 (24%) 539 (42%) 436 (34%) 1282

Type AB 30 (22%) 67 (48%) 41 (30%) 138

Booksb

Yes 534 (21%) 1076 (43%) 879 (35%) 2489

No 189 (22%) 346 (41%) 316 (37%) 851

Beliefc

Yes 432 (20%) 916 (42%) 827 (38%) 2175

No 286 (25%) 490 (43%) 361 (32%) 1137

Languaged

Mandarin 495 (28%) 724 (41%) 546 (31%) 1765

Taiwamese 220 (14%) 679 (45%) 630 (41%) 1529

a Based on school enrollment, which depended on students� national test scores.b Reponses to ‘‘Have you read any books about blood type and personality?’’c Reponses to ‘‘Do you believe there is a relationship between blood type and personality?’’d Language spoken at home.


question, ‘‘Do you believe there is a relationship between blood type and personality?’’ answered yes.About half (53.3%) of the respondents to these questions answered yes to both (data not shown).More than half of the students (53.6%) spoke Mandarin at home. The mean BMI (±SD) for maleswas 21.8 (±3.4) and for females 20.5 (±2.9) (data not shown).

3.2. Association of blood type with personality traits

To assess the association of blood type with personality traits, we used a final multiple regres-sion model controlling for academic achievement, BMI, books read on blood type, belief about ablood type/personality relationship, and the language spoken at home. Histograms of standard-ized residuals for each dependent variable showed the familiar bell-shape curve. The normal prob-ability plots of the residuals showed that the distributions were normal. By plotting studentizedresiduals versus predicted values, we found the residuals falling randomly without any systematictrend. The degree of collinearity was acceptable, with the condition indices and tolerance valuesbelow the cutoff threshold (Hair et al., 1998).

Table 2 shows the unstandardized regression coefficients for the blood types by gender on eachof the five NEO-PI-R domains. In males, Extraversion and Agreeableness included the interactionterms between blood type and belief. Of the stated hypotheses, only the relationship between TypeAB and Conscientiousness was supported by our data. In females, Type AB scored 5 points loweron Conscientiousness compared with Type O females. In comparing the means of the six facets ofConscientiousness among blood types, Type AB females had lower scores for C4 (AchievementStriving), C5 (Self-Discipline), and C6 (Deliberation).

Table 2

Unstandardized regression coefficients with 95% CI for the blood types by gender on each of the five NEO-PI-R

domains using the final multiple regression model

Blood typesa

A B AB

Males

Neuroticism 0.9 (�2.3, 4.0) �1.3 (�4.6, 2.0) 4.1 (�20, 10.2)

Extraversionb

Beliefc (Yes) �3.2 (�6.7, 0.3) 1.3 (�2.4, 5.1) �2.9 (�9.4, 3.7)

Beliefc (No) 3.8 (�0.5, 8.0) �0.8 (�5.1, 3.5) 1.8 (�6.8, 10.3)

Openness 0.1 (�2.0, 2.2) �0.6 (�2.7, 1.6) 0.2 (�3.9, 4.2)

Agreeablenessb

Beliefc (Yes) �0.6 (�3.7, 2.5) 2.6 (�0.7, 5.9) �4.4 (�10.2, 1.4)

Beliefc (No) 2.4 (�1.4, 6.1) 1.0 (�4.8, 2.8) 5.9 (�1.7, 13.5)

Conscientiousness 0.2 (�2.5, 2.9) �1.8 (�4.7, 1.0) �0.1 (�5.3, 5.1)

Females

Neuroticism �1.1 (�4.1, 1.9) �0.5 (�3.5, 2.4) 1.8 (�3.7, 7.3)

Extraversion �0.2 (�2.7, 2.4) �0.0 (�2.5, 2.5) 0.3 (�4.4, 4.9)

Openness �0.9 (�2.9, 1.1) 0.2 (�1.7, 2.2) 0.6 (�3.0, 4.2)

Agreeableness 0.1 (�2.1, 2.3) 0.5 (�1.6, 2.7) �0.9 (�4.9, 3.1)

Conscientiousness 0.2 (�2.4, 2.8) �0.6 (�3.2, 2.0) �5.2 (�10.0, �0.5)*

* P < 0.05.a With blood type O as reference.b The model included the interaction term between blood type and belief.c Reponses to ‘‘Do you believe there is a relationship between blood type and personality?’’


To confirm this result, a 2 · 4 (gender, blood type) MANOVA was performed on the fivedependent variables: Neuroticism, Extraversion, Openness, Agreeableness, and Conscientious-ness. Gender and blood type (A, B, O, AB) were the independent variables. Levene�s test of equal-ity of error variances was nonsignificant for all variables. Multivariate significance testing usingPillai�s test showed that the combined dependent variables were not significantly affected by bloodtype [F(15, 8013) = 0.79, P > 0.05], nor by its interaction with gender [F(15, 8013) = 0.48,P > 0.05].

3.3. The relationship between covariates and personality traits

Table 3 shows the unstandardized regression coefficients for the covariates by gender on each ofthe five NEO-PI-R domain outcomes using the final multiple regression model. Since no hypoth-esis was proposed for these covariates, one must be cautious in interpreting Table 3 results be-cause of potential Type I errors due to multiple significance testing. We found an associationbetween academic achievement and the Extraversion and Openness domains. Males in the highand average academic levels scored 4.1 and 2.2 points lower, respectively, on Extraversion thanthe males in the low academic level did. These data suggest a possible dose response pattern,but no such pattern was found in females. However, females in both the high and average aca-demic levels scored 3.1 points lower on Extraversion than the females in the low academic level

Table 3

Unstandardized regression coefficients with 95% CI for the covariates by gender on each of the five NEO-PI-R domains using the multiple regression

model

Males Academic achievementa BMIb Booksc Beliefd Languagee

High Average

Neuroticism �0.5 (�4.1, 3.0) �1.3 (�4.6, 1.9) 0.3 (�0.1, 0.6) �3.7 (�6.4, �1.0)* 2.7 (0.0, 5.3)* 1.0 (�1.6, 3.6)

Extraversionf

Type A �1.4 (�6.0, 3.1)

No Type A �4.1 (�7.1, �1.0)* �2.2 (�5.0, 0.5) �0.1 (�0.4, 0.3) 5.7 (3.4, 8.1)* 5.9 (3.3, 8.4)* �2.8 (�5.0, �0.6)*

Openness 4.5 (2.2, 6.8)* 1.2 (�1.0, 3.3) 0.2 (�0.1, 0.4) 4.7 (2.9, 6.4)* �0.7 (�1.0, 2.5) 1.0 (�0.7, 2.7)

Agreeablenessg

Type AB �7.8 (�16.9, 1.3)

No Type AB �1.0 (�3.7, 1.7) 0.3 (�2.1, 2.7) 0.1 (�0.2, 0.3) 0.2 (�1.8, 2.3) 2.5 (0.5, 4.6)* 0.0 (�2.0, 2.0)

Conscientiousness 2.1 (�0.9, 5.2) �0.5 (�3.3, 2.2) �0.0 (�0.3, 0.3) 2.0 (�0.9, 3.7) 2.5 (0.4, 4.1)* �1.5 (�3.7, 0.8)

Females

Neuroticism �1.6 (�4.9, 1.7) 2.4 (�0.3, 5.0) 0.1 (�0.3, 0.6) �1.3 (�5.1, 2.4) 2.7 (�0.1, 5.4) 1.2 (�1.3, 0.9)

Extraversion �2.3 (�5.2, 0.5) �3.1 (�5.4, �0.9)* �0.6 (�1.0, �0.3)* 2.8 (�0.4, 5.9) 3.8 (1.5, 6.1)* �1.5 (�3.6, 0.6)

Openness 4.4 (2.2, 6.6)* 1.8 (0.1, 3.6)* 0.0 (0.2, 0.3) 4.4 (1.9, 6.9)* �0.3 (�2.1, 1.5) 2.9 (1.2, 4.5)*

Agreeableness �0.7 (�3.1, 1.7) �1.8 (�3.7, 0.2) 0.0 (�0.3, 0.3) �1.4 (�4.1, 1.3) 1.8 (�0.3, 3.8) �1.2 (�3.0, 0.6)

Conscientiousness 2.7 (�0.2, 5.6) �2.0 (�4.4, 0.3) �0.1 (�0.4, 0.3) 1.9 (�1.3, 5.2) �1.0 (�3.4, 1.4) �1.7 (�3.8, 0.5)

* P < 0.05.a Academic achievement was based on the school enrollment. It was categorized as high, average, or low, with low as reference.b BMI––Body Mass Index [weight (kg)/height2 (m)].c Reponses to ‘‘Have you read any books about blood type and personality?’’ with ‘‘no’’ as reference.d Reponses to ‘‘Do you believe there is a relationship between blood type and personality?’’ with ‘‘no’’ as reference.e Language spoken at home (Mandarin or Taiwanese), with Taiwanese as reference.f Includes the interaction term between blood type A and belief, with Type A compared to all other blood types.g Includes the interaction term between blood type AB and belief, with Type AB compared to all other blood types.

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did. For Openness, males in the high academic level scored 4.5 points higher than males in the lowacademic level did. Females in the high and average academic levels scored 4.4 and 1.8 pointshigher, respectively, than females in the low academic level did. These data suggest that academicachievement is positively associated with Openness and negatively associated with Extraversion.The only significant finding for BMI was found in females where BMI was inversely related toExtraversion.

We also found that the students who had read books on blood type and personality scoredhigher on the Extraversion (males = 5.7, females = 2.8) and Openness (males = 4.7, females = 4.4)domains than those who had not. Those who believed in a relationship between blood type andpersonality scored higher on the Neuroticism (males = 2.7, females = 2.7) and Extraversion(males = 5.9, females = 3.8) domains than those who did not.

4. Discussion

Even with a large representative sample of Taiwanese high school students, we found no signif-icant relationship between blood type and the personality factors as measured by the reliableNEO-PI-R. These results were consistent with recent studies by Cramer and Imaike (2002) andRogers and Glendon (2003) who found no relationship between blood type and the five aspectsof personality. The potential finding from our multiple linear regression analyses that Type ABaffected Conscientiousness was probably due to chance, because our MANOVA analysis didnot support the hypothesis that Type AB would score lower on Conscientiousness. While Eysenck(1982) found that Type AB was related to lower scores on Conscientiousness, Rogers and Glen-don (2003) reported that Type ABs scored higher on Conscientiousness compared to otherrespondents. We agree with Rogers and Glendon (2003) that ‘‘there is no basis for assuming thatpersonality characteristics within a normal population are other than randomly distributedamong individuals with different blood types’’ (p. 1111).

With the advances in molecular genetics, we also agree with Cramer and Imaike (2002) thatusing ABO blood type as a genetic marker for personality has been rendered obsolete. Althoughpsychopathology studies reviewed by Plomin and McGuffin (2003) have reported genetic linkagesfor dementia, reading disability, and hyperactivity, results were less conclusive regarding the effectof DNA on personality. Plomin and Caspi (1998) stated that ‘‘Although failures to replicate havebeen reported, a DNA marker in a gene that codes for one of the dopamine receptors (DRD4) hasbeen associated with novelty seeking’’ (p. 402). They suggested that a possible explanation forthese inconsistent results was inadequate sample size, with a lack of power to detect small effects.Because personality is likely to be influenced by multiple genes, genetic personality researchers willneed to identify the particular genes linked to specific personality traits using adequate sample sizeand statistical power.

We also investigated the relationships between personality factors and the covariates not pre-viously stated in our hypotheses. Because of potential Type I errors in multiple significance test-ing, the interpretation of these results must be cautious. We found that students who had readbooks about blood type and personality were more extraverted and open-minded than thosewho had not. Those who believed that there was a relationship between blood type and person-ality were also more extraverted as well as more neurotic than the students who did not believe.


We also found that academic achievement was positively related to Openness and negativelyrelated to Extraversion. Our results are consistent with the literature. Studies have reported aca-demic achievement to be positively related to Openness to Experience among adolescents aged 11–19 (Schuerger & Kuna, 1987), and undergraduates (Farsides & Woodfield, 2003) and negativelyrelated to Extraversion among undergraduates (Busato et al., 2000; De Fruyt & Mervielde, 1996).Students who are sociable, out-going, talkative, and pleasure seeking may not have the patience orability to concentrate on schoolwork, particularly in the Taiwanese school system that focusesheavily on studying and preparing for national tests. De Raad and Schouwenburg (1996) citingfrom Eysenck (1992) suggest that extraverts would rather socialize than concentrate on studyingand expend their energies in nonacademic activities such as sports.

BMI was also inversely related to Extraversion in our data, but only in females. Extraversionwas the only personality factor related to weight in our findings. This is inconsistent with the re-sults reported by Wade et al. (2003) who studied 102 Caucasian students (38 males and 64 fe-males) ages 18–21, and suggested ‘‘weight did not affect personality rating on the dimensions ofthe Big-5’’ (p. 265). Similarly, Davis and Cowles (1989) studied 64 female athletes and reported‘‘Extraversion proved not to be a predictor of weight’’ (p. 535). It is possible that these studiesshowed no significant relationship between weight and Extraversion because of small sample sizesand the lack of statistical power to detect differences.

On the other hand, overweight Taiwanese high school females who have a low self-esteemmight avoid social interactions that lead to embarrassment. Studies have shown that womenare more concerned about their weight and are generally more dissatisfied with their physicalappearance than men are (Furnham & Calnan, 1998; Furnham et al., 2002). Parızkova and Hills(2001) suggested that obese individuals ‘‘may avoid physical activity and many social contactswherever possible’’ (p. 177). Pierce and Wardle (1997) reported that overweight children havelower self-esteem than children who are not overweight. Furthermore, results have shown thatbeing overweight is inversely related to self-esteem (Israel & Ivanova, 2002), whereas extraversionis strongly correlated with self-esteem (Marlar & Joubert, 2002).

One potential limitation of this study was the accuracy of self-reported blood types. Our pilotstudy found that 92% of the students can accurately recall their blood type, but 8% of the studentswould still be misclassified. Unlike a recent study that can accurately determine the participant�sblood type by using recruited blood donors (Rogers & Glendon, 2003), we depended solely onparticipants� prior knowledge and recall effectiveness.

Another potential limitation was the imposed-etic approach using a translated version of theNEO-PI-R. Emic psychologists believe that the five-factor model originating fromWestern instru-ments may be inadequate to explain underlying personality constructs in Asian cultures (Van deVijver & Leung, 2001). They suggest that importing materials from the US may force raters to use‘‘the possibly Procrustean bed of personality descriptors taken from the English language’’ (Yang& Bond, 1990, p. 1087).

References

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Blood type and the five factors of personality in Asia