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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  

 

 

Relationship between Facial Musculinity and Digit Ratio (2D:4D) Among 
Hausa Taxi and Tricycle Drivers in Kano Metropolis, Niger 

Isyaku Ibrahim1, Anas Ibrahim Yahaya2, Mikail Isyaku Umar3,4, Muhammad Alhaji Buba1 and 
*Emmanuel Ifeanyi Obeagu5  

1 Human Anatomy Department, Faculty of Basic Medical Sciences, Yusuf Maitama Sule University Kano, Nigeria. 
2 Anatomy Department, Faculty of Basic Medical Sciences, Bayero University Kano, Nigeria. 
3 Department of Human Anatomy, Federal University, Dutse, Jigawa State, Nigeria. 
4 Department of Human Anatomy, Kampala International University, Uganda 
5 Department of Medical Laboratory Science, Kampala International University, Uganda.  

Article Info: 
_______________________________________ 
Article History: 

Received 19 June 2023     
Reviewed  27 July 2023 
Accepted 21 August 2023 
Published 15 September 2023 

_______________________________________ 
Cite this article as:  

Ibrahim I, Yahaya AI, Umar MI, Buba MA, 
Obeagu EI, Relationship between Facial 
Musculinity and Digit Ratio (2D:4D) Among 
Hausa Taxi and Tricycle Drivers in Kano 
Metropolis, Niger, Asian Journal of Dental and 
Health Sciences. 2023; 3(3):19-29 

DOI: http://dx.doi.org/10.22270/ajdhs.v3i3.49        

_______________________________________
*Address for Correspondence:   

Emmanuel Ifeanyi Obeagu, Department of 

Medical Laboratory Science, Kampala 

International University, Uganda 

Abstract 
___________________________________________________________________________________________________________________ 

Studies have recognized an association between 2D: 4D ratios and testosterone-dependent traits. The 
aim of the present study is to determine the relationship of 2D: 4D and facial masculinity.  Four hundred 
and two (402) subjects were selected from the two association in Kano state (Tsaya da Kafarka Taxi 
Drivers Association and Tricycle Operators Association Kano (TOAKAN), using random sampling 
methods, the age range of the participants between 18-50 years. The lengths of the 2nd and 4th digits 
were determined by a direct method of measurement. Photographic approaches were used to capture 
the face, facial masculinity was derived from facial distances (captured image face). We use several 
approaches of measuring facial masculinity to study the association with digit ratio. The data were 
expressed as mean ± SD, Pearson correlation was used to quantify the relationships between the 2D: 4D 
and facial masculinity. None of the facial masculine- measures correlated with both right and left 2D:4D 
ratios. 

Keywords: Facial masculinity, 2D:4D (Digit ratio), Photographic methods, Correlation 

 

INTRODUCTION 

Studies have established an association between 2D: 4D ratios 
and testosterone-dependent characters. This investigation 
found such a relationship in the right but not the left hand 1. 
The fourth digit is the ring finger of the human hand and it is 
located between the little finger and middle finger while the 
index finger is the first finger, and it is second digit of the 
human hand. The index finger is situated between the middle 
and the thumb finger and usually the most skilled and 
sensitive finger of the hand but show that males have 
relatively shorter index finger than the ring finger 2. The 
relative of the 2nd and 4th digits lengths (2D:4D) is a sexually 
dimorphic trait in which males have an affinity to have shorter 
2nd digits relative to 4th digits than in females 3.  This showed 
that digit ratio (2D:4D) is standby marker of prenatal 
testosterone 3. Distinct digit ratio (2D:4D) values remain 
comparatively stable across development 4. A study indicated 
the indirect signal that E (estrogen) stimulates the growth of 
the second finger whereas T (testosterone) excites prenatal 
growth of the fourth finger. A low 2D: 4D ratio might act as a 
marker for a uterine environment high in T and low in E, and 
such a ratio is more commonly seen in males. Similarly, a high 
2D: 4D ratio may aid as a marker for a uterine environment 

low in T and high in E, more commonly found in females 1. The 
study between the digit ratios in two-year-old children and the 
levels of prenatal testosterone and estrogen in the amniotic 
fluid for the period of their prenatal development the outcome 
shows that low 2D:4D correlates with high concentrations of 
prenatal testosterone in comparative to estrogen 5. Initial 
exposure to higher levels of T is expected to produce more 
male-like characteristics (masculinization) and less female 
characteristics (defeminisation) 6, whereas less exposure to T 
is expected to produce more female characteristics 
(defeminisation) and fewer male-like characteristics 
(masculinization).  

Facial distances are influenced highly by factors such as sex, 
age, genetic factors and environmental 7,8.  Testosterone (T) 
distressed several facial features, and in Adolescent males, a 
high testosterone-to-oestrogen (T/E) ratio is thought to 
simplify the lateral growth of the chin, mandibles, cheekbones, 
the lengthening of the lower face and the frontward growth of 
the bones of the eyebrow ridges leading to a more robust face 
shape 9. In the pubertal female, the upshot of oestrogen (E) 
leads to a more gracile facial shape with, less robust jaws, 
filled lips and great eyebrows 9. Masculinity is related to 
males’ testosterone (T) exposure during puberty 10. T 

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exposure during development produces several variations in 
the male body, such as the increase of secondary sexual 
characteristics and greater musculoskeletal development 10. 
Nevertheless, T exposure stimuli both human male behaviour 
11 and their physical appearance 12. 

Females and Males have different growth trajectories that 
diverge at puberty for bi-zygomatic width and not for upper 
facial height, leading to a width-to-height facial dimorphism 
(larger ratio in men than in women) that is independent of sex 
difference and enlarged body size 13. Facial masculinity 
founded on a single trait is the eye-mouth-eye (EME) angle. 
Researchers’ deliberation that EME is a sexually dimorphic 
trait, significantly lesser in males 14, even though this sexual 
dimorphism is vague 15. This measure only shows a slight 
correlation with inter-pupillary distance and upper face height 
even though both features define this angle. Certain studies 
have shown that women and men differ in restricted face 
shape at several regions, though particularly at the lower jaw 
16,17. Some of these variances are apparent from an early age. 
Male nose width, as model, is significantly greater from about 
age eight 18. Other methods of measuring masculinity integrate 
several measures of sexually dimorphic features in an index. 
Index 1 simply by adds up standardised measures of cheek-
bone prominence (Upper facial width/lower facial width) and 
lower face length 19. Some index usually employed adds five 
facial measures that show dimorphic differences between 
sexes (eye length, lower face height/face height, cheekbone 
prominence, face width/lower face height and mean eyebrow 
height, all of them divided by interpupillary distance) 20. This 
index  yields higher values when these features are more 
masculine (smaller eyes, smaller eyebrow distance, smaller 
cheekbone prominence, smaller face width and larger lower 
face). 

They engaged three measures that were significantly different 
between sexes: nose width (Nw, larger in men), upper lip 
height (ULh, lower in men) and lower lip height (LLh, lower in 
men). All their measures were summarised as an inter-
pupillary distance percentage. Facial indices of masculinity 
were not associated with 2D:4D 21. The 2D:4D and shape of the 
face differs depending on hormonal presence earlier to the 
onset of puberty, which gives the characteristics of 
masculinity 22.  Research found no significant association 
between 2D:4D and perceptual and structural facial 
masculinity. These studies calculated different indices of 
structural masculinity, using principal components analysis of 
the relative locations of facial landmarks. Though this 
technique may produce indices that accurately reflect 
structural masculinity such indices will, by nature, be averages 
of masculinity. A face with a combination of highly masculine 
and feminine characteristics may receive a score that suggests 
average masculinity. Therefore, it remains possible that 2D:4D 
is associated with localized differences in face shape, i.e., 
differences that occur at specific regions of the face (such as 
the nose or jaw). Growth spurts at puberty further increase 
sex differences, particularly at the mandible 23. The aim of the 
present study is to determine the relationship of 2D: 4D and 
facial masculinity. However, In the present research, we look 
the relationship between a different set of measures of 
masculinity employed by different scholars and digit ratio to 
determine how different facial masculinity correlate with digit 
ratio And find out the hypothesis of association between facial 
masculinity with 2D:4D ratio, which support to the effects of 
prenatal androgens (as indicated by 2D:4D) on facial 
masculinity and femininity similarly, in the previous research 
there was inconsistency with regards to the relationship of 
2D:4D with facial anthropometrics as reported. 

 

MATERIALS AND METHODS 

Study Location 

The present study was conducted in Kano state of Nigeria. The 
rainfall in this part of the country is less than 100cm, with long 
dry season that begins from October and end at April. The 
rainy season is shorter which is just for five months and the 
temperature is between 24- 27ºC and can be as high as 38ºC. 
Kano is the most populous state in Nigeria, with a population 
of 9,383,682 million people. The urban area of the state covers 
137 km2 and comprises of six local government areas (LGAs), 
Tarauni ,Kano Municipal, , Fagge, Dala, Gwale, and Nassarawa 
with a population of 2,163,225 at the 2006 Nigerian census 24, 

25. 

Study Population 

Four hundred and two (402) subjects were selected from the 
male taxi and tricycle drivers within the urban area of the 
State. Seemingly healthy male taxi and tricycle drivers whose 
face and fingers were free from any inflammation, pathological 
changes, or deformity within the age range of 18-50 years who 
was Hausa up to the level of 2 grandparents. 

Ethical Approval and Informed Consent 

Before the commencement of the research, ethical approval 
was sought from the Ethical Committee of the Bayero 
University Kano College of Health Science at Aminu Kano 
Teaching Hospital, Kano. Informed consents were sought from 
the participants. 

Methodology 

Measurement of the Digit Lengths and Determination of 
2d: 4d 

The lengths of the 2nd and 4th digits were determined using a 
direct method of measurement. Following Manning and Tailor 
(Manning & Taylor, 2001), the participants were asked to 
remove rings and the lengths of the 2nd and 4th digits were 
measured directly (using vernier calipers accurate to 0.01 
mm) on the ventral surfaces of both right and left hands from 
the basal crease of the digit to its tip. Every digit was 
measured twice, and the average was taken. When there was a 
crowd of creases at the base of the digit, the most proximal 
crease was considered. Digit lengths measured (in mm) were 
computed for determination of the 2D: 4D by dividing the 2nd 
digit length by the 4th digit length (Plates I). 

 

Plate I:  Photograph Showing the Landmarks for Measurement 
of 2D and 4D Digits 



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Photographs 

The photographic set up comprises of a tripod, supporting a 
digital camera. The tripod was used for modification of height 
of the camera that allows the optical axis of the lens to be 
maintained in a horizontal position during the recording. In 
order to obtain the photographs (frontal), individuals were 
asked to sit and look directly at the camera in front of them 26 
keeping an upright and normal posture, with both arms free 
along the body. This position corresponds to the Broca’s 
Natural Head Position 27, 28.  Each participant was asked to 
ease with both hands hanging beside the trunk. The 
participants were positioned on a line marked on the floor. 
The participants were photographed with a Nikon D40 digital 
camera at 1.00 m and in front of a standard white background, 
while posing in a neutral facial expression. The subjects had to 
look into the lens of the camera with their lips relaxed so that 
the front view profile was taken in the natural head position 
before every recording. The operative ensured that the 
subjects’ neck, ear and forehead, were clearly visible and their 
lip in restfulness.   The tripod helped to avoid undesirable 
movements of operator and camera while taking photographs 
29. Before taking the face, the operator ensured that glasses (if 
worn) had been removed and the participant’s neck,  ears, and 
forehead, were clearly visible during the process 30. After the 
images were captured, they were downloaded to a private 
computer and stored in jpeg format for processing and 
analyses.  

Processing and Analyses 

The captured facial images were imported into a software, bio-
analyser (a software developed using Microsoft visual basic 
version 6). The database was customized with land marks 30 
that was used in the study. The software was used to compute 
all the linear dimension and angles. 

Facial Landmarks Identification 

Standard anatomical landmarks and reference points were 
recognised according to prior works 31-34 and were recognized 

using Bioanalyzer (a software developed using Microsoft 
visual basic version 6) for frontal facial analysis. 

 

Plate II: Landmarks Used for Facial Measurements 33. 

Key:  al; alar, ch; cheilion en; endocanthion, ex; exocanthion, gn; 
gnathion, go; gonion, ls; labiale superious, li; labiale inferious, n; 
nasion, pi; palpebrale inferious, ps; palpebrale superious, sn; 
subnasale, st; stomium, tr; trichion, zy; zygon, ft: frontotemporale. 

Facial Measures of Masculinity 

The facial measures of masculinity used in the present study 
include the following: 

1. Facial width to upper face height ratio (fWHR): This was 
measured as a ratio of the distance between left and right 
zygions (bizygomatic width) and upper facial height (a 
distance between nasion and prosthion) (Plate III) 35.  

  

 

 

Plate III: Upper Facial Height and Width with their Associated Landmarks 35. 

Key: A= Facial Width B= Special Face Height C= Facial Width Height Ratio 

2. Upper Lip Height (ULh), Lower Lip Height (LLh) and Nose 
Width (Nw): These measurements were expressed as 
percentage of interpupillary distance (which is a distance 
measured from the centre of the right pupil to the centre of the 
left pupil.). The upper lip height was determined as the 

vertical distance between the stomion and the labiale 
superius, and lower lip height as the vertical distance between 
the stomion and the labiale inferius. Nose width was measured 
as the horizontal distance between the left and right alares 
(Plate IV) as reported in the previous study. 

A B C 

 



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Plate IV: Upper Lip Height (ULh), Lower Lip Height (LLh) and Nose Width (Nw). 

Key: al: alare st: stomion ls: labiale superior            li: labial inferior 

 

3. Index I: This was determined as the sum of special face 
length/face height and cheek-bone prominence (Plates V). The 
special face length (SFH) was measured as a distance from the 
pupils (corresponding to nasion) to the tip of the chin 
(gnathion) as a proportion of the total face length (FH).  

Cheek-bone prominence was calculated as a ratio of the width 
of the face at cheek- bone (bizygomatic width) (UFW) divided 
by the width of the face at the level of the mouth (bigonion) 
(LFW) 36. 

                          
 

 

 

Plate V: Special Face Length/Face Height and Cheek-Bone Prominence 36 

Key: SFH: Special face height   FH: Face height  UFW: Upper face width LFW: Lower face width n: Nasion                 gn: Gnathion   
 zy: Zygion go: Gonion tr: Trachion 

 

4. Index II: This was determined as sum of eye length, special 
face height/face height and cheekbone prominence, face 
width/special face height and mean eyebrow length (Plate VI), 
all of them divided by interpupillary distance. The eye length 
(EL) was measured by distance between the right and left 
exocanthion minus the distance between the right and left 

endocanthion divided by two (eye length = D1 – D2/2).  2. 
Special face height (SFH)/ face height (FH) was measured as 
the distance of the face from the pupils to the tip of the chin 
over distance of the face from the hairline to the tip of the chin 
D8/ D7. The cheek bone prominence (UFW/LFW) was 
measured as the distance between the left and right zygion 



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(bizygomatic width) over the width of the face at the level of 
the mouth, D3/ D6. Face width (UFW)/special face height (SFH) 
was measured as the distance between the left and right 
zygion (bizygomatic width) over height which was measured 
as the distance of the face from the pupils to the tip of the chin. 
Mean eye brown height (MEBL) was measured as the sum 

right eye brow length (distance from the right outer eye brow 
border to the right inner eye- brow border D9) and left eye 
brow length (distance from the left inner eye brow border to 
the left outer eye- brow border D10) divided by two (2) 17.. 

                              
(
   

  
) (

   

   
)     (

   

   
)       

   

 

 

 

Plate VI. Lower Face Length, Cheek-bone Prominence, Eye Length, and Lower Face Height/Face Height, Face Width/Lower Face 
Height and Mean Eyebrow Length with their Associated Landmarks 17. 

Key: D
1
= Distance between right and left exocanthion D

2 
= Distance between right and left endocanthion D

3 
= Upper face width (UFW) 

D
4 

= Nose width D
5
 = Mouth width, D

6 
= Lower face width (LFW) D

7
 = Face height (FH) D

8 
= Special face height (SFH) 

D
9 

= Right eye brow length  D
10

 = Left eye brow length 

 

5. Index III: This was determined as sum of facial width to 
upper face height ratio (fWHR), upper lip height (ULh), lower 
lip height (LLh) and nose width (Nw), special face length/face 
height (SFH/FH) and cheek-bone prominence (UFW/LFW), 

Eye length (EL), face width (UFW)/special face height (SFH) 
and mean eyebrow length (MEBL), all of them divided by 
inter- pupillary distance (IPD). 

 

         
                 (

   
  

)  (
   
   

)     (
   
   

)        

   
 

 

MEASUREMENT ERROR 

Direct Measurements of Facial Features 

For measurement error analyses, a direct facial 
anthropometry was adopted 34. This involved asking a 
participant to sit with his head in natural head position. A 
digital vernier caliper was then used to measure the facial 
linear dimension of face directly (Plate: VI). This helped in the 
determination of the factor to be used for real size 
measurements of the photographs. The factor was 0.50 which 
was obtained by dividing actual size measurement with actual 
pixel of the image measurement.   

Precision of Measurements 

To calculate precision, the technical error of measurement was 
determined, a set of two measurements were taken with each 
method. These measurements were matched using technical 
error of measurement (TEM). This allowed assessment of 

random error. The TEM (also called the ‘‘method error 
statistic’’) is a standard-deviation−like estimate of error 
magnitude expressed in the original units of measurement. It 
can be used to generate both Intra and inter-observer 
precision estimates. When there are two measurements 
involved, the formula for TEM 37 is as follows:  

Absolute TEM =  ∑di2/2n 

Where ∑d2 = summation of deviations (the difference 
between the 1st and 2nd measurements) raised to the second 
power,  

n = a number of volunteers measured,  

i= the number of deviations 

The absolute TEM was expressed as percentages as follows. 

Relative TEM = Absolute TEM/ VAV × 100  



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Where VAV = Variable average value, is the arithmetic mean of 
the mean between both measurements obtained (1st and 2nd 
measurements) of each volunteer for the same variable. 

This procedure was performed for each of the n participants 
and the n averages obtained and was summed up and divided 
by n (total of a number of participants) 38. The percentage 
scores were divided into five precision categories: scores less 
than 1% was deemed ‘‘excellent,’’ scores ranging from 1% to 
3.9% were deemed ‘‘very good,’’ scores ranging from 4% to 
6.9% were deemed ‘‘good,’’ scores ranging from 7% to 9.9% 
were deemed ‘‘moderate,’’ and scores exceeding 10% were 
deemed ‘‘poor   39.  

Strength of Measurements (r) 

The r was computed to demonstrate the strength of the 
relationship (similarities) between two measurements. Intra-
class correlation (ICC) was used for this purpose. The values 
for the reliability coefficient ranged from 0 to 1, where ICC< 0 
indicated ‘‘no reliability” and 0.6 to <0.8 indicated substantial 
reliability, and 1 indicated almost perfect reliability 40.  The 

interval between two measurements was at least one week. 30 
randomly selected records were used for this evaluation. 
Those dimensions with many differences between the first 
and the second measurements were discarded. 

Statistical Analyses 

The data were expressed as mean ± SD, frequency, and 
percentages. Pearson correlation was used to quantify the 
relationships between the facial masculinity and digit ratio. 
The analyses were carried out using SPSS version 20. P < 0.05 
was considered as level significance 

RESULTS 

Table 1 Shows assessment of technical error of measurements 
(TEM) in linear facial dimensions. It was observed that special 
face height showed the least TEM (1.65%) whereas philtrum 
length showed higher value (9.66%). The rest of the facial 
measurements were also within the acceptable level of TEM 
no variables was greater than 10%. Therefore, all 
measurements were retained.  

 

Table 1: Assessment of Measurement Error in Linear Facial Dimension 

Variables N VAV TEM RTEM% 

zy1_zy2 30 105.16 1.98 1.88 

n_pr  30 64.94 1.84 2.83 

tr_gn 30 186.74 4.20 2.25 

al1_al2 30 46.10 3.21 6.97 

n_gn 30 108.40 1.79 1.65 

go1_go2 30 111.82 2.00 1.79 

ex1_en1 30 27.52 1.29 4.70 

ex2_en2 30 28.23 1.46 5.17 

en1_en2  30 38.82 2.03 5.22 

ls_st  30 11.28 0.71 6.33 

st_li  30 11.59 0.99 8.53 

ebo_ebi  30 43.05 1.04 2.42 

ex1_ex2 30 95.02 2.14 2.25 

sn_gn  30 63.28 5.16 8.15 

g_sn  30 61.67 1.40 2.27 

sn_ls  30 14.67 1.42 9.66 

n_sn  30 45.77 2.74 5.98 

st_gn 30 37.95 1.16 3.05 

ls_li  30 21.79 1.33 6.10 

ps1_pi1 30 10.81 0.65 5.99 

 

 

Table 2 shows another method of the assessment of error in 
the facial dimensions. The higher single measured intra class 
correlation (ICC) was found in Philtrum length (sn-ls) and the 

lowest values found in nose width (al_al). The rest of the 
measurements were greater than 0.89. 

 

 

 

 



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Table 2: Intra-Class Correlation (ICC) Measurements of Facial Dimensions 

S/N VARIABLE MEASUREMANT N ICC 

1 zy1_zy2  Single measures 30 0.944 

Average measures 0.971 

2 n_pr  Single measures 30 0.950 

Average measures 0.975 

3 tr_gn  Single measures 30 0.931 

Average measures 0.964 

4 al1_al2  Single measures 30 0.714 

Average measures 0.833 

5 n_gn  Single measures 30 0.970 

Average measures 0.985 

6 go1_go2 Single measures 30 0.953 

Average measures 0.976 

7 ex1_en1  Single measures 30 0.850 

Average measures 0.919 

8 ex2_en2  Single measures 30 0.794 

Average measures 0.885 

9 en1_en2  Single measures 30 0.744 

Average measures 0.854 

10 ls_st  Single measures 30 0.810 

Average measures 0.895 

11 st_li  Single measures 30 0.759 

Average measures 0.863 

12 ebo_ebi  Single measures 30 0.812 

Average measures 0.896 

13 ex1_ex2  Single measures 30 0.938 

Average measures 0.968 

14 rcp_lcp  Single measures 30 0.921 

Average measures 0.959 

15 sn_gn  Single measures 30 0.946 

Average measures 0.972 

16 g_sn  Single measures 30 0.958 

Average measures 0.979 

17 sn_ls  Single measures 30 0.823 

Average measures 0.903 

18 n_sn  Single measures 30 0.767 

Average measures 0.868 

19 st_gn  Single measures 30 0.940 

Average measures 0.969 

20 ls_li  Single measures 30 0.878 

Average measures 0.935 

21 ps1_pi1  Single measures 30 0.711 

Average measures 0.831 

 



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Table 3 shows the descriptive statistics of the derived facial 
measures of masculinity of the study population. It was 
observed that averaged facial width to height ratio was 
1.71±0.19. Upper lip height (ULh) was 15.86±3.16mm, lower 
lip height (LLh) was 16.53±3.21 and nose width (Nw) was 
68.51±5.33. All the three measures were rendered as 

percentage of interpupillary distance. Upper lip height (ULh) 
was lower than lower lip height (LLh). Averaged Cheek-bone 
prominence was 0.96±0.06. For the Index I, II and III were 
measured as 1.55±0.07, 1.09±0.07 and 108.36 ±11.35, 
respectively.

 

Table 3: Descriptive Statistics of the Derived Facial Measures of Masculinity of the Study Population 

 Parameters Minimum Maximum Mean ± SD 

fWHR. 1.00 2.74 1.71±0.19 

al1_al2:ipd % 53.75 84.02 68.51±5.33 

zy1_zy2 /n_gn (fWSHR) 0.70 1.30 1.00±0.07 

zy1_zy2 /n_gn:ipd 0.00 0.02 0.01±0.00 

n_gn/tr_gn (sFHFHR) 0.50 1.00 0.59±0.04 

n_gn/tr_gn:ipd 0.00 0.01 0.01±0.00 

zy1_zy2/go1_go2 (cbp) 0.75 1.24 0.96±0.06 

zy1_zy2/go1_go2: ipd 0.00 0.02 0.01±0.00 

ls_sti :pd% 8.20 26.39 15.86±3.16 

st_li:ipd% 6.53 25.47 16.53±3.21 

ebo_ebi 32.51 58.68 42.60±4.61 

ebo_ebi:inp 0.49 1.00 0.62±0.05 

El  21.69 43.29 30.18±3.65 

el:inp 0.00 0.56 0.43±0.04 

rcp_lcp 53.38 90.17 69.46±6.59 

Index I 1.32 2.00 1.55±0.07 

Index II 0.88 1.27 1.09±0.07 

Index III 74.63 143.21 108.36 ±11.35 

 

 

Table 4 shows descriptive statistics of digit lengths, digit ratio 
of the study population. The mean value for 2DRight was 
72.18±4.86mm, lower than the 4DRight, which was 

74.09±5.08mm, similar to the left digit. The mean value of 
2DR: 4DR was 0.98±0.04 which was the higher than 2DL: 4DL 
with mean value of 0.96±0.05. 

 

Table 4: Descriptive Statistics of Digit Lengths, Digit ratio 

 Parameters (mm) Minimum Maximum Mean ± SD 

2DR 55.65 87.21 72.18±4.86 

4DR 54.47 88.00 74.09±5.08 

2D:4DR 0.83 1.13 0.98±0.04 

2DL 52.86 87.45 72.15±4.83 

4DL 57.14 90.42 75.10±5.33 

2D:4DL 0.84 1.11 0.96±0.05 

 

 

Table 5 shows correlation between different derived facial 
parameters (measures of masculinity), digit length and ratios. 
It was observed that facial width to height ratio (FWHR) 
showed significant negative correlation with 2DR, 4DR, 2DL 
and 4DL. Nose width/ special face height 
(cZzy1_zy2/n_gn:ipd) showed significant negative correlation 
with 2DR, 4DR and 2DL and 4DL. Cheek-bone prominence 

interpupillary distance (zy1_zy2:go1_go: ipd) showed 
significant negative correlation with 2DR, 4DR and 4DL. It was 
noted that eyebrow length (ebi_ebi) showed significant 
positive correlation with 2DR, 4DR, 2DL and 4DL. Finally, Eye 
length (El) showed significant positive correlation with 2DR, 
4DR, 2DL and 4DL, while Index III was positively correlated 
with 2DL only. 



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Table 5: Pearson’s Correlation between Derived Facial Parameters (Measures of Masculinity) with Digit Length and Ratios 

PARAMETERS (mm) 2DR 4DR 2D:4DR 2DL 4DL 2D:4DL 

fWHR. -0.161** -0.148** -0.014 -0.137** -0.120* -0.022 

al1_al2:ipd% 0.092 0.07 0.025 0.07 0.052 0.019 

zy1_zy2 /n_gn -0.124* -0.110* -0.022 -0.123* -0.052 -0.095 

zy1_zy2 /n_gn:ipd -0.175** -0.160** -0.024 -0.174** -0.115* -0.077 

n_gn/tr_gn 0.09 0.069 0.027 0.085 0.03 0.075 

n_gn/tr_gn:inp -0.064 -0.059 -0.01 -0.063 -0.061 -0.004 

zy1_zy2:go1_go2 -0.067 -0.095 0.043 -0.084 -0.075 -0.008 

zy1_zy2:go1_go2: ipd -0.143** -0.151** 0.012 -0.152** -0.127* -0.029 

ls_st:ipd% -0.022 0.017 -0.054 0.032 0.025 0.016 

st_li:ipd% 0.048 0.043 0.014 0.081 0.057 0.039 

ebo_ebi 0.150** 0.155** -0.01 0.136** 0.143** -0.016 

ebo_ebi:ipd -0.015 -0.025 0.013 -0.049 -0.041 0.003 

El 0.112* 0.106* 0.007 0.141** 0.115* 0.025 

El:ipd -0.02 -0.01 -0.017 0.01 0.017 -0.021 

Right EME -0.042 -0.056 0.021 -0.02 -0.032 0.016 

Left EME -0.036 -0.018 -0.028 -0.037 0.007 -0.064 

Total EME -0.048 -0.047 -0.003 -0.035 -0.016 -0.027 

Index I -0.007 -0.042 0.051 -0.024 -0.047 0.035 

Index II -0.036 -0.037 -0.002 -0.044 -0.03 -0.016 

Index III 0.082 0.082 -0.001 0.100* 0.081 0.026 

*P< 0.05, **P <0.01 

 

DISCUSSION 

From this study, the measurements were found to be 
reproducible with a negligible error for the intra observer 
errors estimated. This was based on the acceptable level of 
TEM reported in the previous study 39. The ICC of the 
measurements have fallen within the prescribed limits as in 
Oliveira et al.41. This has made the results more robust and 
reliable. The minimal error of measurement observed in the 
present study will be have less influence in the interpretation 
of the results in the context of the global data. Similarly, this 
may provide more opportunities to compare results using 
different methodologies. Since, the facial morphometric 
quantified using photogrammetric methods has proved to be 
similar to what was obtained using direct anthropometry with 
the acceptable methods level of error.  

The main objective of this research was to examine different 
approaches of measuring facial masculinity in order to 
standardise the method employed to compute this feature. To 
achieve this aim, we have engaged several methods of 
measuring facial masculinity. We studied how these different 
measures are related to digit ratio. However, as facial 
masculinity has been previously linked to different variables 
based on sex hormone activities right from intra-uterine life, 
we expected at least some of the masculinity measurements to 
correlate with digit ratio. Our main concern is to explain which 
of the different measurement methods are more suitable to 
analyse the association between masculinity and digit ratio. In 
the present study no significant correlation was observed 
between the 2D:4D with indices of masculinity. The absence of 
the correlation may also be attributed to influences of several 
confounding factors such latitude and techniques of finger 

length measurement on 2D:4D as suggested in the literature 
42. 

Contrary to the present study, it was reported that weak but 
significant negative correlations exist between 2D: 4D ratios 
and both masculinity and dominance, supporting their 
argument that high prenatal testosterone levels serve to 
‘organize’ male facial features to subsequently reflect 
dominance and masculine characteristics at puberty 43. But 
this is based on the opposite sex rated facial masculinity, facial 
dominance, and facial attractiveness. It is therefore imperative 
to explain the possible reasons of the discrepancy between 
present finding and literature 43 due to the fact that a face with 
a mixture of highly masculine and feminine characteristics 
may receive a score that suggests average masculinity. 
Therefore, it remains possible that 2D:4D is correlated with 
localized differences in face shape, meaning differences that 
occur at specific regions of the face (such as the nose or jaw). 
Studies have shown that men and women differ in localized 
face shape at several regions, particularly at the lower jaw 44. 
Hence, the subjects rated in the above study v may be have 
more of feminine facial characteristics. 

CONCLUSION 

The main objective of this research was to examine different 
approaches of measuring facial masculinity but none of the 
facial masculine- measures correlated with both right and left 
2D:4D ratios. We therefore recommend further study should 
be carried out on different population and also among 
different ethnic group and larger sample sizes should also be 
used in order to explore more on the relationship between 
facial anthropometry with digit ratio. 



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ACKNOWLEDGMENTS 

I must acknowledge the approval to conduct the study from 
these two noble associations in Kano state, Tsaya da Kafarka 
Taxi Drivers Association Kabuga and Tricycle Operators 
Association Kano (TOAKAN). I would like to express my 
sincere and special appreciation to my mentor Dr A. I. Yahaya 
for his guidance, advice, support. 

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