This article has been cited by other articles in PMC. Abstract Women remain significantly underrepresented in the science, engineering, and technology workforce. Some have argued that spatial ability differences, which represent the most persistent gender differences in the cognitive literature, are partly responsible for this gap.
The underlying forces at work shaping the observed spatial ability differences revolve naturally around the relative roles of nature and nurture. Although these forces remain among the most hotly debated in all of the sciences, the evidence for nurture is tenuous, because it is difficult to compare gender differences among biologically similar groups with distinct nurture. In this study, we use a large-scale incentivized experiment with nearly 1, participants to show that the gender gap in spatial abilities, measured by time to solve a puzzle, disappears when we move from a patrilineal society to an adjoining matrilineal society.
We also show that about one-third of the effect can be explained by differences in education. Given that none of our participants have experience with puzzle solving and that villagers from both societies have the same means of subsistence and shared genetic background, we argue that these results show the role of nurture in the gender gap in cognitive abilities. The debate regarding the origin of this difference is highly emotional. When the President of Harvard University suggested that this gap may be explained by innate differences in abilities 3 , members of the audience left the room.
On the scientific side, many researchers have argued for the important role of nature, and others have argued for the important role of nurture 1 , 4. In this paper we introduce important empirical evidence into this debate. Our study concentrates on gender differences in spatial abilities. Spatial abilities are used in major discoveries in physics and chemistry 1 and are correlated with success in engineering courses 5 , the decision to major in the physical sciences 5 , and performance on the Test of Mechanical Reasoning and the Bennett Mechanical Comprehension Test 6.
The literature reports that men surpass women at spatial reasoning 7. Could this gender gap in spatial reasoning be substantially driven by nurture? There are plausible mechanisms. For instance, spatial skills are influenced by training 8 , 9 , and males typically have relevant training Alternatively, females are stereotyped to have inferior spatial skills, and the salience of negative stereotypes may lead to decreased performance However, direct evidence that nurture matters is lacking.
As our own society became more egalitarian, gender differences in spatial abilities have not shown consistent reductions 6. Additionally, societies promoting gender equality, such as Sweden 12 , Norway 13 , and traditional Kibbutzim in Israel, retain standard gender differences in spatial abilities 14 just like most societies studied Moreover, whereas cross-cultural studies often find main effects of culture on spatial abilities, they rarely find interaction effects between culture and gender The one exception is Canadian Eskimos, who, compared with African Temne, seem to have a smaller gender gap However, the comparison between these societies is hard to interpret, because these societies are not only culturally but also ethnically dissimilar, and this paper fails to report a significant interaction between society and gender.
Results and Discussion Our empirical identification strategy is based on a comparison of two distinct tribes in Northeast India the Khasi and the Karbi that share a genetic background. This comparison allows us to identify the role of nurture. In this region, geographic contiguity is a better predictor of genetic similarity than culture. Both tribes are located in the hills surrounding the city of Shillong, and the Karbi and Khasi appear to be close kin, based on genetic analysis of six polymorphic loci The villagers in both societies are agriculturalist and subsist primarily off rice, with little variation in wealth or diet.
There are many cultural differences between the tribes; thus, we cannot isolate the particular aspect of nurture that matters. However, the most obvious difference between the tribes is that the Karbi are a patrilineal tribe for example, women are not supposed to own land, and the oldest son inherits the property , whereas the Khasi are a matrilineal tribe property is inherited by the youngest daughter, men are not allowed to own land, and any earnings of the male are supposed to be handed over to his wife or sister.
The different societies are described in greater details elsewhere 18 , The participants in the field experiment solved a four-piece puzzle Fig. None of them had previous experience with such a task. Some of our subjects also answered survey questions.