• Journal of Korean Medicine for Obesity Research
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• v.10 no.1
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• pp.41-48
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• 2010

Background The length of the second digit (the index finger) relative to the length of the fourth digit (the ring finger) is sexually dimorphic as males have a lower second to fourth digit ratio (2D:4D). There is evidence that sex differences in 2D:4D arise from in utero concentrations of sex steroids, with a low 2D:4D (male typical ratio) being positively related to prenatal testosterone, while a high 2D:4D (female typical ratio) is positively associated with prenatal oestrogen Objective To investigate possible associations between 2D:4D ratio and sexually dimorphic body composition Methods 2D:4D ratio, body mass index (BMI), waist circumference, waist-hip ratio (WHR), weight, and body fat percentage was measured from 46 men and 20 women Results Digit ratio was found to be significantly lower in men than in women. No significant correlation between 2D:4D ratio and body compositions was found for both men and women while digit ratio in obese men was significantly higher than normal weight men. Conclusion This finding dose not support the significant correlation between digit ratio and sexually dimorphic body composition. However digit ratio in obese men was significantly higher than normal weight men.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.9
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• pp.3983-3990
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• 2012

The hazardous effects of heavy alcohol intake and smoking to body systems have been identified by numerous studies, and there is many influencing factors on alcohol intake and smoking choices. The aim of this study is to identify the correlation between alcohol intake and digit ratio (2D:4D), as well as smoking and digit ratio (2D:4D) in university students. Participants were 121 male and 314 female university students. After filling in questionnaire related alcohol and smoking history, 2nd and 4th finger lengths were measured on both hands using vernier callipers with photocopy. This study showed 2D:4D of the males was 0.95, and that of the females was 0.96. There was a significant difference between male and female in digit ratio. The digit ratio according alcohol intake level significantly differed in only women's left hand. The digit ratio according smoking level significantly differed in only men's left hand. Moreover, The digit ratio was negatively associated with alcohol intake and smoking. The results of this study suggest that the digit ratio (2D:4D) affected with fetal testosterone concentration is negatively related to alcohol intake and smoking. Therefore, the digit ratio would be used in preventive program of alcohol intake and smoking of adolescent, or in antialcoholism /smoking cessation program as a biological basic data.

• Korean Journal of Biological Psychiatry
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• v.18 no.4
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• pp.260-266
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• 2011

Objectives The second to fourth digit ratio (2D : 4D) is known to reflect testosterone level during intrauterine period. Testosterone is essential for masculinization of brain. Cloninger's type II alcoholism is characterized by early age at onset and largely limited to males. Compared with type I alcoholism, type II alcoholism is thought to be masculine. There is a possibility that the digit ratio of type II alcoholism is low compared with type I. We examined digit length ratio in Cloninger's type I and II alcoholism to understand the effects of intrauterine testosterone on the development of alcoholism. Methods The participants were 87 alcohol dependent patients. We divided two subtypes of patients by Irwin's symptom list, based on Cloninger's concept. We captured the images of both palms by the scanner and measured the lengths of digits by the graphic program. Then we analyzed the digit ratios by independent-sample t-test. Results The mean 2D : 4D of type I was 0.942 (right), 0.952 (left). The mean 2D : 4D of type II was 0.927 (right), 0.940 (left). In both hands, 2D : 4D of type II was significantly lower than type I. Conclusions Type II alcoholism showed masculine type of digit length ratio compared with type I. It suggests the exposure of testosterone during intrauterine period might play an important role in determining the course and feature of alcoholism.

• Korean Journal of Biological Psychiatry
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• v.17 no.1
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• pp.37-43
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• 2010

Objectives : The $2^{nd}$ to $4^{th}$ digit length ratio(2D : 4D) is a sexually dimorphic trait regardless of ethnicity and shows sex differences. According to previous research, men usually have a relatively shorter $2^{nd}$ digit than $4^{th}$ digit. There is tendency that men with lower 2D : 4D are perceived as being more masculine and tend to perform better in some physical sports. Furthermore, 2D : 4D is negatively associated with trait aggression. In this study, we examine gender difference of 2D : 4D and compare 2D:4D of female Korean national team members to 2D : 4D of control subjects. Besides that, we also compare 2D : 4D of female Korean national team members according to their sports entries. Methods : The sample of this study is 396 people, 67 female Korean national team member, 216 control women and 113 control men. We measured $2^{nd}$ to $4^{th}$ digit length of their right hand. In addition, we collected demographic information of female Korean national team members using a self-report questionnaire. Results : The mean 2D : 4D of female Korean national team members is 0.96(SD=0.04), smaller than control women's 2D : 4D(0.97, SD=0.03) and significantly higher than control men's 2D : 4D(0.95, SD=0.03). We also found differences between control men and women. Non-martial arts related sports athletes have significant difference with control men in 2D : 4D. However, martial arts related sports athletes' 2D : 4D is not significantly different from other groups, including control men. Conclusion : These results are consistent with the findings of previous research that there is a significant difference between men and women in their 2D : 4D. Furthermore, 2D : 4D of martial arts related sports athletes have not shown any difference from the 2D : 4D of control men that 2D : 4D of non-martial arts related athletes have shown. This fact is important in consideration of masculine characteristics. For further research, it is necessary to examine 2D : 4D difference according to sport ability and gender differences.

• Korean Journal of Biological Psychiatry
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• v.18 no.1
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• pp.25-35
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• 2011

Objectives : Cerebral laterality is thought to be an important marker for neurodevelopment. Prenatal testosterone could influence both cerebral laterality and 2nd to 4th finger length ratio(2D : 4D). EEG coherence and 2D : 4D were examined to investigate the relationship between prenatal testosterone level and cerebral laterality. Methods : EEG was recorded in 24 healthy subjects in the eyes closed resting state. Differences in 2D : 4D finger ratio were used to discriminate "masculine finger type" and "feminine finger type" groups. The 2D : 4D ratio was lower and greater than one for the "masculine finger type" group and "feminine finger type" group, respectively. We used coherence analysis to estimate the cortical functional connectivity. Results : There were statistically meaningful relationships among cerebral functional connectivity, sex and finger ratio. Man and masculine finger type group showed higher intra-hemispheric coherence than those of woman and feminine finger type group. Woman and feminine finger type group showed higher inter-hemispheric coherence than those of man and masculine finger type group. Conclusions : These results imply that prenatal testosterone might act as important determinants of cerebral laterality. Further examination of the relationship between 2D : 4D and EEG coherence in schizophrenia could give some clues for the neurodevelopmental hypothesis of schizophrenia genesis.

• Korean Journal of Biological Psychiatry
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• v.17 no.3
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• pp.136-144
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• 2010

Objectives : The $2^{nd}$ to $4^{th}$ digit length(2D : 4D) ratio reflects the amount of exposure and sensitivity to the prenatal sex hormone and it is considered to be the most convenient and useful way to understand the influence of sex hormone in the determination of human behavioral traits. This study was carried out to find the correlation between the 2D : 4D ratio and characteristics of temperament and character in Korean university students. We assumed that 2D : 4D ratio would show a strong correlation with temperament which is defined to be an inclination of an automatical emotional response to a stimulus. Methods : Participants were 104 university students who completed 2 self-report measures : Temperament and Character Inventory(TCI), Temperament Test. We examined the 2D : 4D ratio of each subject by measuring the lengths of the $2^{nd}$ and $4^{th}$ fingers using a photocopy measurement. We performed statistical analyses using correlation test and t-test to examine the relationship between 2D : 4D ratio and psychological characteristics. Results : We found out the typical sex difference in 2D : 4D ratio. Women had significantly higher 2D : 4D ratio than men. TCI-Character factor(TCI-C) didn't show any significant correlation with the 2D : 4D ratio. TCI-Tempterament factor(TCI-T) and the item of Temperament Test showed a significant correlation with the 2D : 4D ratio. In correlation analysis of the total group including all women and men, the 2D : 4D ratio showed a significant positive correlation in a subscale(shyness with stranger) of harm avoidance scales in TCI-T. In correlation analysis of women's group, the 2D : 4D ratio showed a significant positive correlation in two subscales( fear of uncertainty) and[shyness to stranger] of harm avoidance scales in TCI-T. In correlation analysis of men's group, the 2D : 4D ratio showed a significant negative correlation with a sanguine temperament item of the Temperament Test. Conclusion : The results suggest that the amount of exposure to sex hormone in the prenatal period seems to have an impact on the determination of temperament and characteristics.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.3
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• pp.1245-1251
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• 2013

The aim of this study is to identify characteristics of 2D:4D according to type of handedness. Data was collected from October, 4th, 2010 to April, 30th, 2012. After handedness assessment, 2nd and 4th finger length were measured by vernier calipers. This study showed remarkable gender difference of 2D:4D in left hand for left handers and right hand for right handers, However, there was no significant difference according to type of handedness in each gender. The correlation between left and right 2D:4D in males right handedness was higher than that of male left handedness, otherwise, in case of female, that of left handedness was higher than that of right handedness. The results of this study suggest that the 2D:4D of left handedness does not differ from that of right handedness, however, gender difference and correlation between left and right 2D:4D show different characteristics according to handedness.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.5
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• pp.2170-2177
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• 2012

The ratio of index finger length to ring finger length(2D:4D) is an index of prenatal testosterone and/or estrogen exposure. The aim of this study is to investigate digit ratio and the type of gender-role orientation, to identify the correlation between 2D:4D and gender-role orientation in health and medical students. Participants were 120 male and 146 female university students majoring in health or medicine. After filling in KSRI(Korean Sex Role Inventory), 2nd and 4th finger lengths were measured on both hands using vernier callipers with photocopy. This study showed 2D:4D in the males was 0.95, and that in the females was 0.96 (p<0.01). 38.3% male students revealed androgyny, on the other hand, 35.6% female students revealed undifferentiated type from KSRI. And also, there was a significant difference in masculinity score between male and female but not in feminity score. There was no significant difference in 2D:4D according gender role orientation. The KSRI masculinity score was negatively related to 2D:4D of left hand in male (p<0.05). The results of this study suggest that a more masculine gender role orientation in males is associated with low 2D:4D revealing higher testosterone and/or lower estrogen level in utero. However, more research in 2D:4D ratio to Korean is needed for support of this result.

• Proceedings of the Korea Contents Association Conference
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• 2012.05a
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• pp.409-410
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• 2012

낮은 악력과 높은 악력으로 2등분 했을 때, 손가락 비율(2D:4D)에 대해 낮은 악력을 가진 남자가 높은 악력을 가진 남자보다 더 높은 2D:4D 비율을 가지고 있다. 이와 같은 이론을 토대로, 국내 대학생 중 축구선수를 대상으로 손가락 비율(2D:4D)과 체력과의 상관관계를 분석해보고자 한다.

• Korean Journal of Biological Psychiatry
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• v.21 no.4
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• pp.151-160
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• 2014

Objectives Prenatal testosterone is known to influence both cerebral laterality and 2nd to 4th digit ratio (2D : 4D). Epigenetic changes are thought to play some role in it. We studied sex-related differences between 2D : 4D and cerebral laterality in patients with schizophrenia and controls to examine the effects of prenatal testosterone in the development of schizophrenia. Methods Forty one men (18 schizophrenic patients and 23 controls) and 40 women (17 schizophrenic patients and 23 controls) were recruited from one psychiatric hospital in Korea. The 2D : 4D and electroencephalographic (EEG) coherence in 19 channels (66 pairs of interhemispheric coherence and 54 pairs of intrahemispheric coherence) were measured. The sex-related statistical analyses between 2D : 4D and EEG coherence in controls and patients with schizophrenia were performed using multiple regression. Results In male patients, the relationship between 2D : 4D and right intrahemispheric EEG coherence showed mainly positive correlation in delta and theta frequency bands, while it showed negative correlation in male controls. In female patients, the relationship between 2D : 4D and interhemispheric EEG coherence showed stronger positive correlation in alpha and beta frequency bands, while it showed weaker positive correlation in female controls. Conclusions Low prenatal testosterone may play certain roles in altered correlation between 2D : 4D and cerebral laterality in schizophrenia and the development of schizophrenia by epigenetic mechanism.