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Introduction
One of the most frequently asked questions today is
which profession young individuals are more likely to
pursue or should pursue. Although various psychological
and biological tests and methods have been utilized
throughout history, providing a definitive answer to this
question remains challenging. However, comparative,
easily applicable, and low-cost tests may offer insights.
Measurements related to an individual’s physical struc-
ture, for instance, can provide clues about their person-
ality traits, which could potentially simplify career selec-
tion. Digit ratios are one such commonly used measure-
ment tool in physical assessments.[1]
The digit ratio, denoted as 2D:4D, refers to the ratio
of the length of the 2nd digit (index finger = 2D) to the
length of the 4th digit (ring finger = 4D).[2] These mea-
surements are obtained by measuring from the midpoint
of the basal creases on the ventral surface of the hand,
where the digits meet the hand, to the tip of the digit
(Figure 1).
There is evidence suggesting that the 2D:4D ratio
negatively correlates with prenatal testosterone exposure
Digit ratio: comparative analysis between
professional volleyball players and medical
students
Ozan Turamanlar1 , İlknur Çöllü1 , Önder Çalışkan2
1Department of Anatomy, Faculty of Medicine, Izmir Kâtip Çelebi University, Izmir, Türkiye
2Department of Physiotherapy and Rehabilitation, Faculty of Health Sciences, Mudanya University, Bursa, Türkiye
‹D ‹D ‹D
Abstract
Objectives: The ratio of the length of the 2nd digit to the 4th digit of the hand, known as the digit ratio (2D:4D), has been
widely studied in health, behavioral, and sports sciences as a potential indicator of prenatal testosterone exposure. This study
aimed to compare the 2D:4D ratios of male individuals who are athletically and academically successful and to evaluate
whether 2D:4D can serve as a marker for occupational selection, talent identification, and the impact of individual charac-
teristics on job performance.
Methods: This study included 32 male professional volleyball players and 39 male medical students. The lengths of the 2nd and
4th digits of both hands were measured using a digital caliper, and the 2D:4D ratio was calculated. The dominant hands of the
participants were also recorded for analysis.
Results: Intra-group comparisons of the right-hand and left-hand 2D:4D ratios within both the student and volleyball play-
er groups showed no statistically significant differences (p=0.225; p=0.922). Inter-group comparisons of the 2D:4D ratios for
the right hand and left hand were also statistically similar (p=0.388; p=0.939). Additionally, the difference between the right-
hand and left-hand 2D:4D ratios (Dr-l) did not differ significantly between the groups (p=0.525). Comparisons based on dom-
inant hand preferences revealed no statistically significant findings.
Conclusion: This study highlights the need for larger, multicenter studies with more participants to further explore the poten-
tial relationship between 2D:4D ratios and occupational or performance traits. We hope this research serves as a foundation
for future investigations and provides valuable insights for researchers in this field.
Keywords: digit ratio; medical students; performance; 2D:4D; volleyball players
Anatomy 2024;18(3):83–90 ©2024 Turkish Society of Anatomy and Clinical Anatomy (TSACA)
Original Article
http://dergipark.org.tr/en/pub/anatomy
Received: September 22, 2024; Accepted: December 12, 2024
doi:10.2399/ana.24.1586683
This study was an oral presentation at 24th National Anatomy Congress, 19th–21st September, 2024, Istanbul, Türkiye
84 Turamanlar O, Çöllü İ, Çalışkan Ö
Anatomy • Volume 18 / Issue 3 / December 2024
and positively correlates with estrogen levels.[3,4]
Specifically, a low 2D:4D ratio is associated with higher
prenatal testosterone and lower estrogen levels, while a
high 2D:4D ratio correlates with lower testosterone and
higher estrogen levels during fetal development.[4,5]
The 2D:4D ratio has been widely recognized as a
potential marker of prenatal testosterone exposure across
various fields, including health, behavioral sciences, and
sports sciences. Research suggests that prenatal andro-
gens influence brain development, enhancing its sensi-
tivity to testosterone later in life. These hormones are
thought to regulate brain structure and function, with
2D:4D often considered a reliable indicator of athletic
potential.[6–8] A low 2D:4D ratio has been linked to suc-
cess in financial endeavors, admission to medical schools,
and strong performance in sports such as basketball, ski-
ing, and football.[9–13] Elevated levels of fetal androgens
are believed to contribute to the development of the car-
diovascular system, improve visual-spatial skills, enhance
physical stamina and speed, and increase tendencies
toward aggressive behavior—traits that may provide
competitive advantages in sports.[12,13]
The relationship between 2D:4D and academic per-
formance has also been explored,[14–18] with some studies
showing a negative correlation between 2D:4D and aca-
demic success.[14,16] However, there is limited research
comparing individuals excelling in both physical and
cognitive domains. Therefore, this study aims to com-
pare the 2D:4D ratios of male individuals who are suc-
cessful in sports with those who excel in academic fields.
By doing so, we seek to investigate whether 2D:4D can
serve as an indicator for career selection, talent identifi-
cation, and assessing the impact of individual character-
istics on job performance.
Materials and Methods
Power analysis for two independent groups determined
that the minimum required sample size was 68, with at
least 32 participants in one group and 36 in the other.
Under these conditions, the test power was estimated to
be approximately 81.03%. In this study, we compared
two groups: 32 male professional volleyball players com-
peting in the top league (Efeler League) under the
Turkish Volleyball Federation, and 39 male students
from the Faculty of Medicine at Izmir Kâtip Çelebi
University. The lengths of the 2nd and 4th digits of both
hands were measured using a digital caliper (Rohs Norm
2002/95/EC) after obtaining informed consent from all
participants. The 2D:4D ratio was calculated, and the
dominant hands of the participants were recorded
(Figure 1).
The exclusion criteria for this study included individu-
als with systemic diseases, finger anomalies or pathologies
in any extremity, those under 18 years of age, and female
participants to eliminate gender-related differences.
Additionally, among the university student participants,
individuals who engaged in any form of sports, even at an
amateur level, were excluded.
Data analysis was conducted using IBM SPSS
Statistics, version 26.0 (IBM Corp., Armonk, NY, USA).
Summary statistics were presented as frequencies (n), per-
centages (%), mean ± standard deviation (9± sd), median
(M), minimum (min), and maximum (max) values. The
Shapiro-Wilk test was used to assess the normality of
numerical data, while the Levene test evaluated the homo-
geneity of variances. For comparisons between two
groups, the “Independent two-sample t-test” was applied
when parametric assumptions were met; otherwise, the
“Mann-Whitney U test” was used. Intra-group and inter-
group comparisons of right and left hand measurements
Figure 1. Measurement of digit lengths, left hand. 2D: 2nd digit length;
4D: 4th digit length.
85
Digit ratio: comparative analysis between professional volleyball players and medical students
Anatomy • Volume 18 / Issue 3 / December 2024
were analyzed using “Mixed Order ANOVA.” Statistical
significance was defined as p<0.05.
Results
The number of participants and their hand dominance are
presented in Table 1. The 32 volleyball players had an
average age of 26.96 years, an average height of 193.40 cm,
and an average weight of 83.75 kg (Table 2). The 39 uni-
versity students had an average age of 20.74 years, an aver-
age height of 178.64 cm, and an average weight of 75.16 kg
(Table 3).
Intra-group comparisons of the right-hand and left-
hand 2D:4D ratios within the student and volleyball play-
er groups showed no statistically significant differences
(Table 4). Similarly, inter-group comparisons of the right-
hand and left-hand 2D:4D ratios were statistically similar
(Table 4). The inter-group comparison of the difference
between the right-hand and left-hand 2D:4D ratios (Dr-l)
also showed no significant differences (Table 5).
When participants were grouped by hand dominance,
the right-hand 2D:4D, left-hand 2D:4D, and Dr-l values
were statistically similar for both right-handed (Table 6)
and left-handed dominant participants (Table 7). Of the
total participants, 64 were right-handed dominant and 7
were left-handed dominant. Analysis of right-hand 2D:4D,
left-hand 2D:4D, and Dr-l values, grouped by dominant
hand, did not yield any statistically significant results
(Table 8).
Table 1
Participant characteristics.
Right-handed Left-handedn Total
Participant n (%) (%) (n)
Volleyball players 29 (90.62%) 3 (9.38%) 32
University students 35 (89.74%) 4 (10.26%) 39
Total 64 (90.14%) 7 (9.86%) 71
n: number of participants.
Table 2
Demographic characteristics of volleyball players.
Variables n Min-Max Mean±SD
Age (years) 32 18–49 26.96±8.33
Height (cm) 32 180–210 193.40±7.19
Weight (kg) 32 68–112 83.75±9.68
Max: maximum; Min: minimum; n: number of participants; SD: standard deviation.
Table 3
Demographic characteristics of university students..
Variables n Min-Max Mean±SD
Age (years) 39 19–26 20.74±1.48
Height (cm) 39 160–191 178.64±7.47
Weight (kg) 39 54–111 75.16±12.91
Max: maximum; Min: minimum; n: number of participants; SD: standard deviation.
Table 4
Comparison of 2D:4D values within and between groups.
Groups Test statistics*
Student Player Fp-value η2
2D:4D value Right 0.9863±0.0408 0.9932±0.0212 0.754 0.388 0.011
Left 0.9921±0.0429 0.9927±0.0247 0.006 0.939 0.001
Test statistics† F=1.498 F=0.010
p=0.225 p=0.922
η2=0.021 η2=0.001
F: mixed design ANOVA; η2: effect size; *comparison between groups: †comparison within groups. Descriptive statistics are given as mean±standard deviation. The sta-
tistical significance level is p<0.05.
86 Turamanlar O, Çöllü İ, Çalışkan Ö
Anatomy • Volume 18 / Issue 3 / December 2024
Table 5
Comparison of Dr-l (right hand) in groups (2D:4D minus left hand 2D:4D difference).
Groups Test statistics
Student Player z-value p-value
Dr-l 9±sd -0.0058±0.0338 0.0005±0.0229
0.636 0.525
M (min-max) -0.0021 (-0.10–0.07) -0.0002 (-0.06–0.06)
9: mean; sd: standard deviation; M: median; z: Mann-Whitney U test.
Table 6
Comparison by group in right dominant hands (Dr-l:Right hand 2D:4D minus left hand 2D:4D difference).
Groups Test statistics
Student Player Test value p-value
2D:4D right 9±sd 0.9874±0.0412 0.9938±0.0226
z=0.636 0.525
M (min-max) 0.9939 (0.9008–1.1092) 0.9942 (0.9509–1.0356
2D:4D left 9±sd 0.9921±0.0433 0.9927±0.0264
z=0.298 0.766
M (min-max) 0.9854 (0.9031–1.1041) 0.9893 (0.9550–1.0669)
Dr-l 9±sd -0.0047±0.0350 0.0011±0.0243
t=0.753 0.454
M (min-max) 0 (-0.10–0.07) 0.0006 (-0.06–0.06)
9: mean; sd: standard deviation; M: median; t: independent two-sample t test; z: Mann-Whitney U test.
Table 7
Comparison by group in left dominant hands (Dr-l: Right hand 2D:4D minus left hand 2D:4D difference).
Groups Test statistics
Student Player t-value p-value
2D:4D right 9±sd 0.9733±0.0416 0.9893±0.0072
0.775 0.474
M (min-max) 0.9850 (0.9270–1.0079) 0.9910 (0.9769–0.9955)
2D:4D left 9±sd 0.9915±0.0475 0.9930±0.0047
0.063 0.952
M (min-max) 1.0131 (0.9370–1.0244) 0.9918 (0.9891–0.9991)
Dr-l 9±sd -0.0182±0.0091 -0.0037±0.0081
0.221 0.078
M (min-max) -0.016 (-0.03–0.01) -0.025 (-0.01–0.0)
9: mean; sd: standard deviation; M: median; t: independent two-sample t test.
Table 8
Comparison according to the dominant hand (Dr-l: Right hand 2D:4D minus left hand 2D:4D difference).
Groups Test statistics
Right handed dominant Left handed dominant z-value p-value
2D:4D right 9±sd 0.9902±0.0342 0.9824±0.0260
0.775 0.474
M (min-max) 0.9940 (0.9008–1.1092) 0.9877 (0.9270–1.0079)
2D:4D left 9±sd 0.9924±0.0366 0.9923±0.0276
0.501 0.616
M (min-max) 0.9877 (0.9031–1.1041) 0.9944 (0.9370–1.0244)
Dr-l 9±sd -0.0022±0.0307 -0.0099±0.0110
0.215 0.210
M (min-max) 0.0006 (-0.10–0.07) -0.0100 (-0.03–0.0)
9: mean; sd: standard deviation; M: median; z: Mann-Whitney U test.
Discussion
Prenatal testosterone levels may play a pivotal role in
excelling at certain sports activities. Traits influenced by
testosterone, such as muscle fiber growth, enhanced
strength, reduced fat mass, and elevated hematocrit levels,
are likely contributors to athletic success.[19] The 2D:4D
ratio has been shown to correlate with performance in var-
ious individual and team sports, including basketball, ski-
ing, volleyball, fencing, and football.[12,13,20–22]
In a study comparing athletes in judo, wrestling, and
kickboxing with a control group of non-athletes, the
2D:4D ratio was found to be significantly lower in the
athlete group.[23] This finding aligns with research sug-
gesting that a low 2D:4D ratio is associated with elevat-
ed testosterone levels and tendencies toward aggression,
traits often beneficial in combat sports.[24–26] Additionally,
athletes participating in contact sports have been report-
ed to have significantly lower 2D:4D ratios compared to
those in non-contact sports.[7] Reed and Meggs[7] found
that athletes in contact sports exhibited both lower
2D:4D ratios and higher physical aggression compared
to their non-contact counterparts.
The population of study included the male athletes
belonged to a professional volleyball team, representing
a non-contact sport. The lack of a statistically significant
difference in the 2D:4D ratio among professional ath-
letes in our study may be attributed to their involvement
in a non-contact sport.
Manning et al.[26] found that the right-hand 2D:4D
ratio is more sensitive to prenatal sex steroids than the
left-hand 2D:4D. Similarly, Hönekopp and Watson,[25]
in their 2010 meta-analysis, reported higher prenatal
androgenization in the right-hand 2D:4D compared to
the left-hand 2D:4D. Research on 2D:4D generally
examines both right- and left-hand ratios, while also
considering the difference between them (Dr-l) as an
additional marker. This difference, calculated as the
right-hand 2D:4D minus the left-hand 2D:4D, has been
proposed as a negative marker for prenatal testosterone
exposure and a positive marker for prenatal estrogen
exposure.[26] Dr-l is sexually dimorphic, with males con-
sistently exhibiting lower values than females. This dis-
tinction emphasizes its potential as a marker for prenatal
hormone exposure. Hill et al. identified a negative cor-
relation between lower Dr-l values and VO2 max.[27]
VO2 max, the maximum rate of oxygen consumption
during exercise, reflects cardiovascular capacity and
determines the upper limit of performance in endurance
sports.[28] The regulatory effects of prenatal testosterone
on the developing cardiovascular system may influence
aerobic performance levels later in life.
Kim et al.[29] also reported that the right hand tends
to exhibit stronger sex differences and is more sensitive
to prenatal androgens compared to the left hand. For
instance, in a study conducted on female Olympic ath-
letes, only the right-hand 2D:4D showed a significant
difference compared to the control group, while in
another study on gymnast girls, the left-hand 2D:4D did
not show a significant difference from the control
group.[30,31] Although the digit ratio of the right and left
hands was not found to be associated with hand prefer-
ence, the Dr-l (difference between right-hand and left-
hand 2D:4D) was shown to be linked to hand preference.
Studies have found that left-handed individuals exhibit
significantly lower Dr-l values compared to right-hand-
ed individuals.[32,33] This suggests that considering hand
dominance in future research may help in interpreting
the results more accurately. The results of our study
showed no significant relationship between Dr-l and
hand dominance in the statistical analyses. However, this
result may be attributed to the relatively small sample
size, which could have limited the statistical power to
detect significant differences. It is suggested that future
studies with larger sample sizes be conducted to clarify
this relationship.
It is recognized that 2D:4D ratios vary among indi-
viduals from different ethnic groups, regardless of sport.
In a study, average 2D:4D values were reported to differ
between ethnic groups, irrespective of gender.[34]
Therefore, ethnic differences should be considered in
future research, as the current study was conducted on a
Turkish population. In a study conducted in India, vol-
leyball players were compared with a control group, and
the 2D:4D ratios of both hands were found to be signif-
icantly lower in volleyball players. However, no statisti-
cally significant difference in Dr-l was observed between
the volleyball players and the controls.[21] In the present
study, male university students with no prior involve-
ment in sports were compared with professional male
volleyball players, but no significant differences were
detected in the statistical analysis.
In a study examining the association between 2D:4D
and performance in both practical and theoretical exams
among dental students in Brazil, a significant negative
correlation was found between 2D:4D and exam scores
in male students.[16] Similarly, Coco et al.[14] reported a
87
Digit ratio: comparative analysis between professional volleyball players and medical students
Anatomy • Volume 18 / Issue 3 / December 2024
88 Turamanlar O, Çöllü İ, Çalışkan Ö
Anatomy • Volume 18 / Issue 3 / December 2024
notable relationship between 2D:4D and success in med-
ical school entrance exams in Italy. Additionally, a mul-
ticenter study conducted across Russia and the
Philippines identified a non-linear, quadratic correlation
between 2D:4D and academic success.[17]
It has been proposed that prenatal testosterone influ-
ences cognitive abilities, such as intelligence and learn-
ing, by affecting key developmental processes, including
neuronal proliferation, migration, differentiation, and
apoptosis. This influence is thought to enhance the den-
sity of neural networks in specific brain regions.[35]
Prenatal exposure to testosterone may directly affect
intelligence by altering neuronal migration, leading to
greater development of the right hemisphere and
improved coordination within and between hemi-
spheres.[36] This process promotes the development and
organization of dense neuronal networks in areas associ-
ated with cognition, learning, and memory, potentially
through reduced apoptosis or increased neuronal migra-
tion to these regions during development.[6,35] Androgens
have also been shown to have an organizational effect on
brain development, suggesting that prenatal testosterone
may act as a programming mechanism that influences
behavior later in life.[37] Supporting this, a study found
that individuals presenting with “boxer’s fracture” had
significantly lower 2D:4D ratios compared to the gener-
al population, linking 2D:4D to physical and behavioral
traits associated with testosterone exposure.[38]
It has been reported in several studies that no signif-
icant correlation exists between 2D:4D and physical per-
formance. It has also been suggested that claims regard-
ing a relationship may be somewhat overstated. Based on
these findings, it is indicated that 2D:4D is unlikely to
serve as a reliable predictive marker for athletes’ physical
performance and abilities.[39–41] In the present study, the
absence of statistically significant differences in the
results may be attributed to the limited sample size and
the lack of additional measurement parameters.
Conclusion
Studies have shown that digit ratios can reflect perfor-
mance across various domains. In our study, compar-
isons were made between volleyball players who had
achieved a high level of physical performance and medi-
cal students who demonstrated their abilities through
academic success. No significant differences were found
between the measurement results of the two groups. It is
suggested that the lack of differences observed in our
study may stem from the fact that both groups excelled
in their respective fields. This indicates that 2D:4D may
be more closely associated with behavioral characteris-
tics rather than being limited to specific activities or pro-
fessions.
Future studies should consider larger sample sizes
and include a broader range of populations. It would also
be valuable to examine the relationship between digit
ratios and specific psychological or personality traits
using validated tests. However, it is essential to approach
such associations cautiously, taking into account the
potential influence of cultural differences on the validity
and reliability of these tests.
We believe that our study can serve as a foundation
for more detailed analyses to be conducted in multicen-
ter studies with larger participant groups. It also provides
a valuable perspective for researchers interested in
exploring this area further.
Conflict of Interest
All authors participating in the study declare that there is
no conflict of interest regarding the study.
Author Contributions
OT: project development, data management, data analy-
sis, manuscript writing, manuscript editing; İÇ: project
development, data collection, data analysis, manuscript
writing, manuscript editing; ÖÇ: data collection.
Ethics Approval
Necessary permissions for this study were obtained from the
Izmir Kâtip Çelebi University Clinical Research Ethics
Committee (approval number: 2022/587). The study was
conducted in accordance with the principles outlined in the
Declaration of Helsinki on Human Rights.
Funding
None.
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90 Turamanlar O, Çöllü İ, Çalışkan Ö
Anatomy • Volume 18 / Issue 3 / December 2024
Correspondence to: İlknur Çöllü, MD
Department of Anatomy, Faculty of Medicine,
Izmir Kâtip Çelebi University, Izmir, Türkiye
Phone: +90 507 258 02 10
e-mail: ilknurcollu1@gmail.com
Conflict of interest statement: No conflicts declared.
This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 Unported (CC BY-NC-
ND4.0) Licence (http://creativecommons.org/licenses/by-nc-nd/4.0/) which permits unrestricted noncommercial use, distribution, and reproduction in any
medium, provided the original work is properly cited. How to cite this article: Turamanlar O, Çöllü İ, Çalışkan Ö. Digit ratio: comparative analysis
between professional volleyball players and medical students. Anatomy 2024;18(3):83–90.
ORCID ID:
O. Turamanlar 0000-0002-0785-483X;
İ. Çöllü: 0000-0003-1605-6327;
Ö. Çalışkan: 0009-0000-5537-258X
