The 2D:4D ratio, hand dominance, and gender

  • Helen Protopapas Wilfrid Laurier University
  • Pamela J Bryden Wilfrid Laurier University

Abstract

The ratio of the difference between the 2nd and 4th digits of the hand (2D:4D ratio) has been demonstrated to be an indirect indicator of prenatal testosterone levels. Prenatal testosterone has been found to play a role in brain development in utero, and thus may influence lateral asymmetries, such as handedness. The aim of the current study was to examine the 2D:4D ratio, hand preference, and hand performance measurements across different age groups. 25 individuals between 5-15 years old (x?age = 8.6, females = 14), 35 individuals between 20-30 years old (x?age = 24, females = 21), and 27 individuals 50 years or older (x?age = 59.67, females = 15) participated in the study and completed the Waterloo Handedness Questionnaire (WHQ) as an indicator of hand preference and the Tapley-Bryden Dot Marking (TBDM) task to evaluate hand performance. Right and left 2D:4D ratios were measured for all participants using Vernier calipers, measured to the nearest 0.01mm. No main effects were found for the 2D:4D ratios across the age groups. There was a main effect of handedness regardless of age, F(1,90) = 40.87, p<0.001, where right-handers had greater WHQ scores compared to left-handers. Also, a significant interaction between gender and age groups was found for the TBDM task, F(3,74) = 2.82, p<0.05, where females had larger hand performance differences between the hands compared to males in the 50 years or older age category. These results are suggestive that hand measurements can be influenced by age when gender and handedness are considered.

Acknowledgments: NSERC