Comparing the 2D:4D finger-
length ratio of males and
females
Kalisvaart, L.
ID: i6215145
Tutorial group 04
Faculty of Health, Medicine and Life Sciences (FHML)
Maastricht University
Course BBS1001
12th October, 2019
1
, 1. Introduction
During pregnancy in humans the fetus is constantly getting hormone signals through the
placenta. For instance, a recent experiment has indicated that there is a connection between
the balance of testosterone and estrogen exposure in amniotic fluid during pregnancy and
the distance of length between the second and fourth finger (1). This difference in length
between the second and fourth finger is called the 2D:4D ratio. The relationship of the 2D:4D
ratio and the balance of testosterone and estrogen exposure is the strongest in the right
hand (2).
The testosterone and oestrogen levels in amniotic fluid can also have influences on the
development of serval disorders like autism, dyslexia, migraine and even breast cancer. So
the 2D:4D ratio can be predictive of disease and can be used in diagnosis and prognosis (3).
A low 2D:4D ratio means that the ring finger is longer compared to the index finger. Men’s
ring fingers are normally longer than their index fingers, and therefore males have a low
2D:4D ratio. For females it is contradictory, because females normally have a higher 2D:4D
ratio.
Different traits can be dependent by either having a low or high 2D:4D ratio. For instance, the
shape regression of the facial landmark coordinates upon the 2D:4D ratio. Some
characteristics landmarks that are more typically for males correlate with a low 2D:4D ratio,
but a high 2D:4D ratio correlate with characteristics which are considered as more female
like(4).
A study has shown that males with a lower 2D:4D ratio are more likely to be aggressive than
males with a higher 2D:4D ratio (5). Another study has shown that male homosexuals and
bisexuals have a higher 2D:4D ration than heterosexuals(6). However, in these studies there
is no relationship found for females.Animal tests on mice showed that mice with a high
testosterone levels or a low estrogen levels had lower ratios, more likely for males. On the
contrary, mice with a higher estrogen level or a lower testosterone level had higher ratios,
more female like ratios. This experiment showed that there is indeed a connection between
the balance of testosterone and oestrogen and 2D:4D(7).The results from the studies
indicate that a high or a low 2D:4D ratio should be sex-linked. Here we made a comparison
between the 2D:4D ratio of male and female first year students biomedical sciences at
Maastricht University.
2
length ratio of males and
females
Kalisvaart, L.
ID: i6215145
Tutorial group 04
Faculty of Health, Medicine and Life Sciences (FHML)
Maastricht University
Course BBS1001
12th October, 2019
1
, 1. Introduction
During pregnancy in humans the fetus is constantly getting hormone signals through the
placenta. For instance, a recent experiment has indicated that there is a connection between
the balance of testosterone and estrogen exposure in amniotic fluid during pregnancy and
the distance of length between the second and fourth finger (1). This difference in length
between the second and fourth finger is called the 2D:4D ratio. The relationship of the 2D:4D
ratio and the balance of testosterone and estrogen exposure is the strongest in the right
hand (2).
The testosterone and oestrogen levels in amniotic fluid can also have influences on the
development of serval disorders like autism, dyslexia, migraine and even breast cancer. So
the 2D:4D ratio can be predictive of disease and can be used in diagnosis and prognosis (3).
A low 2D:4D ratio means that the ring finger is longer compared to the index finger. Men’s
ring fingers are normally longer than their index fingers, and therefore males have a low
2D:4D ratio. For females it is contradictory, because females normally have a higher 2D:4D
ratio.
Different traits can be dependent by either having a low or high 2D:4D ratio. For instance, the
shape regression of the facial landmark coordinates upon the 2D:4D ratio. Some
characteristics landmarks that are more typically for males correlate with a low 2D:4D ratio,
but a high 2D:4D ratio correlate with characteristics which are considered as more female
like(4).
A study has shown that males with a lower 2D:4D ratio are more likely to be aggressive than
males with a higher 2D:4D ratio (5). Another study has shown that male homosexuals and
bisexuals have a higher 2D:4D ration than heterosexuals(6). However, in these studies there
is no relationship found for females.Animal tests on mice showed that mice with a high
testosterone levels or a low estrogen levels had lower ratios, more likely for males. On the
contrary, mice with a higher estrogen level or a lower testosterone level had higher ratios,
more female like ratios. This experiment showed that there is indeed a connection between
the balance of testosterone and oestrogen and 2D:4D(7).The results from the studies
indicate that a high or a low 2D:4D ratio should be sex-linked. Here we made a comparison
between the 2D:4D ratio of male and female first year students biomedical sciences at
Maastricht University.
2
