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Finger length linked to exam scores

May 24, 2007
Courtesy University of Bath
and World Science staff
Updated May 28

Mea­sure­ments of chil­dren’s fin­ger lengths ap­pear to pre­dict their scores on math and lit­er­a­cy tests, re­search­ers have found.

The study might raise anew the con­tro­ver­sial is­sue of wheth­er boys and girls have dif­fer­ent in­nate abil­i­ties, sci­en­tists said. This is be­cause fin­ger length is pro­posed to be re­lat­ed to dif­fer­ences in hor­mones re­spon­si­ble for de­ve­lop­ment­al dif­fer­ences in boys and girls.

In a study to ap­pear in the Brit­ish Jour­nal of Psy­chol­o­gy, re­search­ers com­pared the fin­ger lengths of 75 seven-year-old chil­dren with stand­ard­ized test scores. They found what they called a clear link be­tween math and lit­er­a­cy per­for­mance and the rel­a­tive lengths of their in­dex and ring fin­gers.

The researchers said the link is thought to stem from dif­fer­ent lev­els of the hor­mones tes­tos­ter­one and oes­tro­gen in the womb. Tes­tos­ter­one is be­lieved to pro­mote de­vel­op­ment of brain ar­eas “often as­so­ci­at­ed with spa­tial and math­e­mat­i­cal skills,” while oes­tro­gen may do the same for ver­bal abil­ity, said study lead­er Mark Bros­nan, head of the Un­ivers­ity of Bath, U.K. psy­chol­o­gy de­part­ment.

“In­ter­est­ingly, these hor­mones are al­so thought have a say in the rel­a­tive lengths of our in­dex and ring fin­gers. We can use mea­sure­ments of these fin­gers as a way of gaug­ing the rel­a­tive ex­po­sure to these two hor­mones in the wom­b.” Tes­tos­ter­one and oes­tro­gen are al­so re­spon­si­ble for the de­vel­op­ment of male and female sex­u­al char­ac­ter­is­tics, re­spec­tive­ly.

The re­search­ers meas­ured chil­dren’s fin­gers and di­vid­ed the length of the in­dex fin­ger by that of the ring fin­ger. The in­ves­ti­ga­tors found that a smaller ra­tio—that is, a long­er ring fin­ger with res­pect to index finger—was linked to bet­ter scores in math com­pared to lit­er­a­cy. This fin­ger con­fi­gur­ation also sig­nals great­er pre­na­tal tes­tos­ter­one ex­po­sure, they said.

When in­ves­ti­ga­tors stud­ied boys’ and girls’ per­for­mance sep­a­rate­ly, they found a link be­tween high pre­na­tal tes­tos­ter­one ex­po­sure as meas­ured by dig­it ra­tio, and high­er math scores in ma­les. They al­so found a link be­tween low pre­na­tal tes­tos­ter­one ex­po­sure, which re­sulted in a shorter ring fin­ger com­pared with the in­dex fin­ger, and high­er lit­er­a­cy scores for girls.

The re­search­ers gauged pu­pils’ abi­li­ties us­ing the Stand­ardized As­sess­ment Test, a U.K. test un­re­lated to the SAT exams given to U.S. high school stu­dents. 

“We’re not sug­gest­ing that fin­ger length mea­sure­ments could re­place SAT tests” of which­ever kind, said Bros­nan. “Fin­ger ra­tio pro­vides us with an in­ter­est­ing in­sight in­to our in­nate abil­i­ties in key cog­ni­tive ar­eas. We are al­so look­ing at how dig­it ra­tio re­lates to oth­er be­havioural is­sues, such as techno­pho­bia, and ca­reer paths. There is al­so in­ter­est in us­ing dig­it ra­tio to iden­ti­fy de­vel­op­mental dis­or­ders, such as dys­lex­ia, which can be de­fined in terms of lit­er­a­cy de­fi­cien­cies.”

Boys on av­er­age tend to out­per­form girls in math on stand­ard­ized tests, but the rea­sons why are dis­put­ed. Some stud­ies have found that male and female in­fants have dif­fer­ent ten­den­cies and in­ter­ests from the first day of life. On the oth­er hand, new re­search has found that stereo­types of male math su­pe­ri­or­ity, by them­selves, prompt girls to per­form worse on tests. 

Sci­en­tists asked to com­ment on the finger-length study last week did­n’t dis­pute that it might pro­vide ev­i­dence bear­ing on the de­bate. But they urged cau­tion in in­ter­pret­ing the find­ings. Some not­ed that finger-length is on­ly an in­di­rect in­dic­a­tor of pre­na­tal hor­mone ex­po­sure. Finger ratio is just a “proxy” for hor­mone ex­po­sure, which can also be meas­ured di­rect­ly in the am­ni­ot­ic flu­id where the fe­tus floats, noted Si­mon Baron-Cohen of Ox­ford Uni­ver­si­ty, U.K., who has ex­ten­sive­ly stud­ied ma­le-female brain dif­fer­ences.

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Measurements of children’s finger lengths appear to predict their scores on math and literacy tests, researchers have found. The study might raise anew the controversial question of whether boys and girls have different innate abilities, scientists said. This is because finger length is proposed to be related to differences in hormones responsible for differing sexual characteristics in boys and girls. In a study to appear in the British Journal of Psychology, scientists compared the finger lengths of 75 seven-year-old children with standardized test scores. They found what they said was a clear link between performance in math and literacy tests and the relative lengths of their index and ring fingers. Scientists believe that the link is caused by different levels of the hormones testosterone and oestrogen in the womb. Testosterone is believed to promote development of brain areas “often associated with spatial and mathematical skills,” while oestrogen may do the same for verbal ability, said study leader Mark Brosnan, head of the University of Bath, U.K. psychology department. “Interestingly, these hormones are also thought have a say in the relative lengths of our index and ring fingers. We can use measurements of these fingers as a way of gauging the relative exposure to these two hormones in the womb.” Testosterone and oestrogen are also responsible for the development of male and female sexual characteristics, respectively. The researchers measured children’s fingers and divided the length of the index finger by that of the ring finger. The investigators found that a smaller ratio—that is, a longer ring finger and therefore greater prenatal testosterone exposure—was linked to better scores in math compared to literacy. When investigators studied boys’ and girls’ performance separately, they found a link between high prenatal testosterone exposure as measured by digit ratio, and higher numeracy SAT scores in males. They also found a link between low prenatal testosterone exposure, which resulted in a shorter ring finger compared with the index finger, and higher literacy SAT scores for girls. This, says the scientists behind the study, suggests that measurements of finger length could help predict how well children will do in maths and literacy. “We’re not suggesting that finger length measurements could replace SAT tests,” said Dr Brosnan. “Finger ratio provides us with an interesting insight into our innate abilities in key cognitive areas. We are also looking at how digit ratio relates to other behavioural issues, such as technophobia, and career paths.” “There is also interest in using digit ratio to identify developmental disorders, such as dyslexia, which can be defined in terms of literacy deficiencies.”