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Available online at ajdhs.com 

Asian Journal of Dental and Health Sciences 
Open Access to Dental and Medical Research 

Copyright  © 2023 The  Author(s): This is an open-access article distributed under the terms of the CC BY-NC 4.0 
which permits unrestricted use, distribution, and reproduction in any medium for non-commercial use provided the 

original author and source are credited  

 

 

The Study of 2D:4D Ratio and Facial Asymmetry Using Eye-Mouth-Eye 
Angle among the Student of College of Medicine and Health Sciences, 
Federal University Dutse 

Mikail Isyaku Umar1,2, Abba Ishaq1, Ibrahim Ahmad Atiku1, Ni'imah Rabiu El-Yakub1, Musa Abubakar3 and 
*Emmanuel Ifeanyi Obeagu4  

1 Department of Human Anatomy, Federal University Dutse, igawa State, Nigeria 

2 Department of Human Anatomy, Kampala International University Uganda. 

3 Department of Human Anatomy, Bayero University Kano, Kano State, Nigeria. 

4 Department of Medical Laboratory Science, Kampala International University, Uganda.  

Article Info: 
_______________________________________ 
Article History: 

Received 02 July 2023     
Reviewed  13 August 2023 
Accepted 28 August 2023 
Published 15 September 2023 

_______________________________________ 
Cite this article as:  

Umar MI, Ishaq A, Atiku IA, El-Yakub NR, 
Abubakar M, Obeagu EI, The Study of 2D:4D 
Ratio and Facial Asymmetry Using Eye-Mouth-
Eye Angle among the Student of College of 
Medicine and Health Sciences, Federal 
University Dutse, Asian Journal of Dental and 
Health Sciences. 2023; 3(3):37-41 

DOI: http://dx.doi.org/10.22270/ajdhs.v3i3.52        

_______________________________________

*Address for Correspondence:   

Emmanuel Ifeanyi Obeagu, Department of 
Medical Laboratory Science, Kampala 
International University, Uganda.  

Abstract 
___________________________________________________________________________________________________________________ 
Deviations of physical characteristics from bilateral symmetry, in otherwise symmetric individuals, are 
supposed to result from environmental perturbations during development. One cause of such 
perturbations may be sex steroids such as testosterone and oestrogen. The study examined the 
relationship between second to fourth digit ratio (2D:4D), a putative negative correlate with prenatal 
testosterone and a positive correlate with prenatal estrogen, and asymmetry. The hand of the 
participants was place on a flat surface with the palm facing upward fore arm in line with the middle 
finger. Finger should be extended maximally and dose to each other measurement technique was 
followed for measuring 2D:4D digit length which can be define as a distance between the proximal 
flexion crease of the digit length was measured in centimeters. Table 1 shows descriptive analysis of 2D 
and 4D right and left distance. The minimum and maximum ages are 18 and 35 years respectively. The 
mean of 2D:4D right length was 0.98 ± 0.015 and the mean of 2D:4D left length 0.97 ± 0.022 this shows 
there is higher mean value in right 2D:4D length. Our data show that both low 2D:4D (a marker of high 
prenatal testosterone) and high 2D:4D (a marker of high prenatal estrogen) are associated with 
elevated levels of asymmetry and this relationship applies particularly to finger asymmetry. 

Keywords: 2D:4D ratio, facial asymmetry, eye-mouth-eye angle, students 

 

INTRODUCTION 

Many human body parts undergo development with bilateral 
symmetry. This implies that the right and left sides can be 
divided into identical mirror images. However, due to 
biological factors inherent to processes of development as well 
as environmental disturbances, perfect bilateral symmetry is 
rarely found. The term asymmetry is used to make reference 
to dissimilarity between homologous elements, altering the 
balance between structures. Facial asymmetry is common in 
the overall population and is often presented sub-clinically 1. 
Facial asymmetries manifest themselves very early in human 
development and remain during lifetime [2]. Randomly 
distributed deviations from perfect symmetry in paired traits 
such as ear height and wrist width are thought to reflect 
perturbations during development 2.  

2D:4D is the study of finger length patterns, namely the length 
of the second relative to the length of the fourth digit (digit 
ratio, 2D:4D).  Eye-mouth-eye angle is a quantitative and face 
size independent trait that is sexually dimorphic and a good 
indicator of masculinity and face symmetry 3. Using frontal 

photographs of both male and female faces 4. Facial 
asymmetry is the condition that one half of the face is not 
equivalent as the other half 5.  

MATERIAL AND METHOD 

Study Area 

The study will be conducted in Federal University Dutse, 
Jigawa State. 

Study Population  

The study population will comprise of all the students of 
College of Medicine and Health Science of about 750 students 
in the Faculty of Basic Medical Science and Faculty of Clinical 
Science. 

Student Design  

The study was a descriptive cross sectional study using 
Anthropometry. 

 

                       Open Access                                                                                                                                                                                                         Research Article                                          

http://dx.doi.org/10.22270/ajdhs.v3i3.52
https://crossmark.crossref.org/dialog/?doi=10.22270/ajdhs.v3i3.52&amp;domain=pdf
https://orcid.org/0000-0002-4538-0161


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Sample size determination 

The subjects for the study were the student of Faculty of Basic 
Medical Science, Federal University Dutse. The sample size 
was determined using standard formula that recognizes the 
total population precision level, confidence interval and 
standard deviation. 

N≥Z2a2S/d2 

Where n=Sample size, Z=Normal distribution value, 
d=Detection level considered S=Standard deviation of the 
sample database on previous knowledge. 

Inclusion criteria  

The following subject are included in the research 

i- Subject that are within the Faculty of Basic Medical Sciences 
and Faculty of Clinical Sciences, Federal University Dutse. 

ii- Subject that are within the age range of 18-35years 

iii-Subject that are physically fit without any form of deformity 

Exclusion criteria  

The following are excluded in the research 

i- Subject with craniosynostosis   

ii- Subject that are symbrachydactyly 

iii- Subject that are oligodactyly 

Ethical consideration 

A letter of introduction was collected from the department of 
Human Anatomy Federal University Dutse, and was taken to 
the ethical committee of Faculty of Basic Medical Sciences 
Federal University Dutse. The aim and objectives of the study 
were explained to the committee and their permission were 
obtained. The explanations of the procedure as well as the 
intended use of the research were properly addressed to the 
subject and their consents for the participation were obtained.                                                                                               

Methods 

Step 1  

Sample size and participant 150 participants of student (79 
male and 71 female) of Federal University Dutse, particularly 
from Faculty of Basic Medical Science (Human Anatomy, 
Human Physiology and MBBS). Were recruit for the research 
study, Participants range in age from 18 to 35 years. Research 
study was conduct in only one faculty in the university, each 
participant was required to fill the questionnaire contain basic 
demographic profile (e.g., sex, age, ethnicity, etc.). Participant 
were giving information regarding the research study and 
measurement, procedure and were assure about the 
confidentiality of the data, they provide and are require to a 
sign a consent form before participant in the study. 
Participants with any hand, face, diseases, injury, and 
deformity were excluding from the research study. 

Step 2 

The hand of the participants was place on a flat surface with 
the palm facing upward fore arm in line with the middle 
finger. Finger should be extended maximally and dose to each 
other measurement technique was followed for measuring 
2D:4D digit length which can be define as a distance between 
the proximal flexion crease of the digit length was measured in 
centimeters with help of both the right and left hands and 
repeat three (3) time tor accuracy and mean value Was taken 
for statistical analysis with 0.002.302 as measurement error. 

All the measurements were performed during the time period 
9:00am-12:00pm to eliminate durational variations and under 
the same conditions to avoid inter-observer errors. 

Morphometric Measurements 

Two (2) morphormetric measurements are record for each 
hand. 

2DL (Length of index finger) It is measurement as the distance 
between the mid-point of metacarpo-phalangeal crease at the 
base of index finger of index to the tip or most forwardly 
placed point of the index finger.  

4DL (Length of the ring finger) It is measured as the distance 
between the mid-point of metacarpo-phalangeal crease at the 
base of ring finger to the tip or most forwardly place point of 
the ring finger. 

2D:4D Digit Ratio Measures 

2D:4D digit ratios are computed by during length of the index 
finger with the length of the ring finger. 

                                     2D Length of index finger 
2D:4D Digit Ratio = _______________________________                          
                                     4D Length of ring finger 

 

Facial Measurement 

The use of FA as a measure of developmental stability and 
variation may be an important way in the assessment of level 
of stress in a given population. This information is scanty in 
cited literature among Hausa population. Exploring sexual 
dimorphism in FA may be considered as the rate limiting step 
in determining which group between males and females is 
more prone to developmental stress among Hausa population 
6. 

For each trait, FA was calculated by subtracting the left from 
the right-side value. The repeatability of the two independent 
FA measurements was tested using a one-factor, repeated 
measures ANOVA 7. Measures were accepted as being 
repeatable if there was a significantly greater variance 
between individuals than between the repeated FA 
measurements of the same individual. Repeatability estimates, 
based on the interclass correlation of the variance component 
of the repeated measures ANOVA, were also determined.  

 Trait that showed significant repeatability can only be 
accepted as showing FA if the signed asymmetries are 
normally distributed (as determined by a Shapiro-Wilk test) 
around a mean of zero (determined by a one-sample t-test 
with the null hypothesis set to a mean of zero). Absolute mean 
FA were scaled according to trait size by dividing each one by 
the average value of the trait measurements. Composite FA 
was then calculated as the sum of the individual scaled Fas 6. 

Step 3 

The third part of our study we establish sexual dimorphism of 
the eye-mouth-eye angle using men’s faces (Age of 18 to 
35years) and women’s faces (Age of 18 to 35years). They were 
student from college of medicine and health sciences Faculty 
of Basic Medical Science and Clinical Science of Federal 
University Dutse between 2018 and 2022. Eye-Mouth-Eye 
angle are measure with the protractor in the middle of the 
mouth and arms crossing the center of the pupils. It is 
measure by the protractor with the accuracy of one degree. 

Step 4 

The fourth part of our study investigates the relationship 
between2D 4D ratio, and eye-mouth-eye angle value and eye-
mouth-eye bilateral asymmetry. We used the student of 
Federal University Dutse, Faculty of Basic Medical Science, and 
clinical Science. The entire student they were also asked to 
have a neutral expression on their faces. Participants sat on a 
stool, 150 students measured the angle to assess the level of 



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asymmetry between the right and left part of the angle. The 
right part of the angle was measured between the line that 
started in the midline define by two anthropological point 
stomiom (middle of the mouth) and nasion similarly, but with 
the line that ended in the middle of the pupil. Measured the 
left part of the eye-mouth-eye angle. 

Asymmetries were calculated by the difference between the 
left and the right part of the eye-mouth-eye angle. Whether the 
distribution of asymmetry is skewed to one of the facial halves 
(because of the possibility of facial lateralization), subtracted 
the right part of the angle from left one rather than using the 
absolute values of this difference, obtain plus value if the right 
is larger. The facial height and width and the right and left 
width of the nose and length of the nose were measured. The 
right and left eye width were also measured. The width and 
height of the mouth were also measured. 

 

Statistical analysis                                                                                                       

The data obtained was transported from Microsoft application 
(word and excel). Data were expressed as mean ± standard 
deviation (SD). Student’s t-test was used to test for the 
difference in height, weight, 2D, 4D between female and males. 
Linear and multiple linear regressions were applied to test the 
predictive ability of 2D and 4D on height and weight. 
Statistically significant difference was deemed acceptable at P 
< 0.05. Sigma Stat 2.0 for Windows (Systat Inc., Point 
Richmond, CA) was used for the statistical analysis.   

RESULTS 

Table below shows the descriptive analysis of 2D and 4D right 
and left length. The minimum and maximum ages are 18 and 
35 years respectively. The mean of 2D:4D right length was 
0.98 ± 0.015 and the mean of 2D:4D left length 0.97 ± 0.022 
this shows there is higher mean value in right 2D:4D lengths.

 

Table 1: Descriptive analysis of 2D:4D ratio among the student of College of Medicine and Health Sciences, Federal 
University Dutse 

Variable                             Minimum                                 Maximum                              Mean±SD                           

Right   2D:4D                        0.945                                         1.032                      0.9851± 0.01519 

Left      2D:4D                         0.933                                        1.022                      0.97706± 0.02213 

 

Table below shows the variation of sexual dimorphism in 2D:4D digit ratio, there is higher mean value in 2D:4D right and there is 
clear significant differences in both the right and left 2D:4D digit ratio. 

 

Table 2:   Sexual Dimorphism in 2D:4D among the student of College of Medicine and Health Sciences, Federal University 
Dutse 

Mean ± SD 

 

 

                                                      Variable                   Male                               Female                                t-value        p-value 

 

 Right 2D:4D            0.990±0.0156            0.98±0.0121                    5.032          0.01 

   Left    2D:4D            0.978± 0.0141           0.975±0.0285                 0.608         0.544 

 

The table below shows the sexual dimorphism in facial asymmetry using eye-mouth-eye angle and there is higher mean value in 
ASYM-1 of male from the combination of R.EME and L.EME, and there is slightly lower mean value in ASYM-2 of female from the 
combination of R.EME and L.EME. 

 

Table 3: Sexual dimorphism in facial asymmetry using eye-mouth-eye angle among the student of College of Medicine and 
Health Sciences, Federal University Dutse 

 

Mean ± SD 

                                                          Variable          Male                                Female                          t-value                   P-value 

                                                          ASYM              1.0102±0.0385            1.0017±0.0191           1.68                         0.094 

 

  

 

 



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The table below shows the significant relationship between 2D:4D digit ratio and facial asymmetry which determine that, there is 
negative or no correlation differences between ASYM and 2D:4D digit ratio.    

TABLE 4: Relationship between facial asymmetry (eye-mouth-eye angle) and 2D:4D ratio among the student of College of 
Medicine and Health Sciences, Federal University Dutse                                                            

 ASYM R. 2D:4D L. 2D:4D SEX CD 

ASYM 1 0.251 -0.018 -0.137 

  0.0021 0.824 0.094 

     

R. 2D:4D  1 0.097 -0.382 

   0.239 0 

     

L. 2D:4D   1 -0.05 

    0.544 

     

SEX CD    1 

     

 

 

DISCUSSION 

Digit lengths (the length of 2nd digit otherwise known as 
index finger and that of the 4th digit also known as ring finger) 
was measured on the ventral surface of the hand from the 
basal crease of the digit to the tip of the finger using a digital 
venier caliper measuring to 0.05mm. In order to reduce 
observation errors, Digit length measurements were read 
twice independently and the mean of the two measurements 
was taken as the actual value. Students with a history of 
fractures in the fingers or any form of deformity on the digits 
that could hinder accurate measurement 8. 

In a related study by Else vier Churchill Livingstone; 2005 
conducted among forensic marker 2D:4D ratio derived from 
the index and ring finger length in males varied from 0.89 to 
1.03 (mean 0.9678 and S.D 0.02224)   hand and 0.89 to 1.02 
(mean 0.9689 and S.D 0.02582) for the left hand. In female 
2D:4D ratio varied from 0.92 to 1.09 (mean 1.0145 and S.D 
0.02896) for right hand and 0.92 to 1.09 (mean 1.0142 and S.D 
0.02986) for the left hand. Depicts the descriptive statistics 
range, mean, standard deviation, standard error for2D:4D 
ratios for both hands and for both sexes. The derived 2D:4D 
ratio show statistically significant sexual dimorphism at level 
P <0.001. However no significant difference was found for 
right and left hands for both the sexes. As found in previous 
studies [9-10], males had a lower average 2D:4D ratio than 
females both on the right hand and on the left hand and the 
mean differences were significant both with a parametric t-
test                                   

(2D:4D right hand; males 0.969G0.036, females 0.983G0.034, 
Tzk2.16, pZ.032, two-tailed; 2D:4D left hand, males 
0.965G0.038, females 0.985G0.040, tZK2.89, pZ.004, two-
tailed) and a non-parametric permutation test (right hand; 
pZ.016, left hand; pZ.003). 

In related study ratio of 2D:4D (Index finger: Ring finger) has 
been shown to be more sensitive, despite other digit ratios 
(3D:5D) displaying sexual dimorphism and relationship to 
various human phenotypic traits. Existing literature also 
shows accumulating evidence on 2D:4D ratio showing 
correlations with various traits in humans. 

 It is thus considered to be a proxy marker of prenatal 
androgen exposure. A longer index finger will result in a ratio 
higher than 1, while a longer ring finger will result in a ratio of 
less than 1. The second digit is typically shorter in both males 
and females, while the difference in length of the two digits is 
greater in males than in females. 

In related study Gray, 2004 they examined whether there 
were any age differences between two sexes. The Mann-
Whitney U testevealed no significant age differences between 
sexes (U=2.278.0, p=0.08). The mean value of the EME angle 
for women was 50.16◦  (SD=2.71, n=71), and for men it was 
47.68◦  (SD=2.42, n=79), and this difference between sexes 
was significant, (146) = 5.58, p=0.0001. Using Cohen’s effect 
size criterion for interpreting mean differences, (i.e., 
0.2=small, 0.5=medium, 0.8=large, we found that this 
difference was quite large (Cohen’s  d=0.970). 

In previous study we confirmed the results of Frackiewiczs 11 
that men and women are sexually dimorphic on the EME angle 
character, and this difference was quite large (d=0.97). We 
found that male faces with relatively smaller EME angles 
Frackiewicz 11 were perceived by women as more attractive. 
These findings suggest that EME is valuable even in a highly 
homogenous population. 

In accordance with previous reports 10, males had a 
significantly lower 2D:4D ratio than females on the right hand 
but no significant sex difference was found on the left hand 
2D:4D right hand; males x=0.95F0.02, females x=0.99F0.02, 
t=7.82, P <.05, 2D:4D left hand, males x=0.96F0.03, females 
x=0.99F0.02, t=4.92, P <.05. We found that 2D:4D ratio was 
significantly correlated with facial asymmetry scores in both 
sexes. Male right-hand 2D:4D ratio corrected significantly 
negatively with facial asymmetry (r=.260; P=.029). Female 
right hand 2D:4D ratio correlated significantly positively with 
facial asymmetry, (r= .228; P=.031). Left hand 2D:4D and facial 
asymmetry were significantly negative correlated in males 
(r=.319; P= .009), but there was no significant correlation in 
females (r= .020; P= .436). 

The aim of the previous study was to examine possible 
relationships between finger length ratio and facial 
asymmetry in males and females. Male facial asymmetry was 
negatively correlated with 2D:4D in both hands, but only in 



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the right hand in females. These relationships probably reflect 
in utero organizational effects of sex steroids on facial 
asymmetry rather than adult hormone effects 12. 

CONCLUSION 

The correlation between 2D:4D digit ratio was observed that 
the mean value in right 2D:4D of both male and female were 
higher. 

The correlation between the variable was positively higher 
between 2D:4D ratio of the right and negatively higher 
between 2D:4D ratio of the left and there was statistically 
significant difference in both right and left ratio (p< 0.05) of 
both genders. 

There was statistically significant different (p< 0.05) in the 
right and left 2D:4D digits ratio and asymmetry (eye-mouth-
eye angle) of both gender male and female.  

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https://doi.org/10.1017/S0006323197005082
https://doi.org/10.1037/0735-7036.121.2.221
https://doi.org/10.1080/02699930903485076
https://doi.org/10.1037/0096-1523.22.3.662
https://doi.org/10.4103/aoba.aoba_32_16
https://doi.org/10.1016/S1090-5138(03)00052-7
https://doi.org/10.1016/S1090-5138(03)00052-7
https://doi.org/10.18778/1898-6773.64.07
https://doi.org/10.18778/1898-6773.64.07
https://doi.org/10.1016/S1090-5138(03)00084-9

