The ratio of second and fourth finger lengths (2D:4D) can determine handedness

Abstract

Objective: The human body exhibits both structural and functional asymmetry. One measure of this asymmetry is the ratio of 2D:4D, which is the proportion of measurements of the 2nd (2D) and 4th finger (4D). In this research, our objective is to investigate the potential association between the ratio of 2D:4D and handedness with voluntary individuals. Methods: A total of 312 individuals volunteered to take part in the research, where their left and right hand's 4th and 2nd finger lengths were measured using a precise digital caliper. The "Edinburgh Handedness Inventory" was used to determine hand lateralization. To determine the significance between the two independent groups, the Mann Whitney U Test was used. On the other hand, to determine the significance between the two dependent groups, the Wilcoxon Signed Rank Test was utilized. Results: Of the participants, 154 were male and 158 were female (age range 18-55, mean age=28.34). According to the Edinburgh Handedness Inventory, 275 individuals were right handed, 18 were left handed, and 19 were bimanual. The Mann Whitney U Test showed a significant result in the ratio of right hand 2D:4D between male and female participants who were right handed (z =-1.979, p = 0.048). Additionally, the Wilcoxon Signed Ranks Test demonstrated a difference between the right and the left hand ratio of 2D:4D for all participants which was significant (z = -2.822, p = 0.005), as well as for participants who were right handed (z = -2.850, p = 0.004). Conclusion: The ratio of 2D:4D finger lengths could be a significant indicator of hand preference in both male and female healthy individuals. The ratio of 2D:4D holds potential as an indicator and research tool in understanding human emotions, thoughts, and behaviors.