Prenatal Testosterone Exposure and Numerical Competence in Children and Adults

Brookes, Helen (2011) Prenatal Testosterone Exposure and Numerical Competence in Children and Adults. Doctoral thesis, Northumbria University.

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Abstract

The present thesis sought to investigate the potential relationship between the second to fourth finger ratio (2D:4D), as a somatic marker of prenatal testosterone exposure, and basic numerical skills in children and adults. Chapter 1 presents a basic overview of the nature and effects of sex steroids followed by a more comprehensive consideration of literature regarding the reported effects of prenatal testosterone (PT) on the brain and cognition. The chapter then more specifically considers the possible influence of PT on numerical and mathematical competencies.

Experiment 1 attempted to replicate evidence for a relationship between 2D:4D and basic numerical skills in children. The results revealed only one significant correlation, namely a significant positive correlation between right hand 2D:4D and number comparison scores in females.

Chapter 3 discussed research regarding the nature and characteristics of so called ‗core‘ numerical competencies. Experiments 2-4 then attempted to explore any relationship between 2D:4D and performance on tasks designed to assess such skills in adults. The results of all three studies revealed an association between 2D:4D and lateralization for the process of subitizing relative to a comparable control task. The nature of this observed effect however varied across the three experiments.

Experiment 4 also identified significant positive correlations between left hand 2D:4D and counting reaction times in females and a series of two way interaction effects between 2D:4D and task (numerical vs. control) for subitizing, counting and number comparison performance. The revealed interactions predominantly suggested faster task reaction times/higher accuracy in high 2D:4D (low PT) participants as compared to low 2D:4D (high PT) participants on the numerical tasks and the opposite pattern of results (i.e. high 2D:4D associated with poorer performance) on the control tasks.

Experiment 5 investigated the association between 2D:4D and core numerical skills in children. Significant correlations were observed between; left hand 2D:4D and subitizing reaction times to the left visual field in males (negative direction), right hand 2D:4D and subitizing reaction times the right visual field in females (positive direction) and left hand 2D:4D and subitizing percentage error scores to the right visual field in females (negative direction). A possible relationship between 2D:4D and lateralization for both subitizing and number comparison relative to control was also found. For both numerical tasks low 2D:4D participants showed a right visual field advantage and high 2D:4D participants showed a left visual field advantage while different patterns of results were shown on the control task.

Experiment 6 re-considered the relationship between 2D:4D and basic and core numerical skills in children using a standardised assessment of numerical competencies (the Dyscalculia Screener). No significant correlations however between 2D:4D and performance were identified.

Finally, experiment 7 re-examined evidence for a link between 2D:4D and Key Stage 1 Standardised Assessment Test (SAT) scores. While the findings did not replicate evidence for a direct link between 2D:4D and SAT numeracy scores the results did demonstrate a significant negative relationship between right hand 2D:4D minus left hand 2D:4D (Dr-1; higher scores thought to indicate lower exposure to PT) and SAT numeracy scores in females. Such findings may potentially suggest a facilitative influence of PT on numeracy in women.

Overall, while a number of interesting findings were revealed, limited consistency was identified across the results of the experiments conducted in the present thesis. The findings therefore offer no concrete support for a possible association between 2D:4D and basic numerical skills in either children or adults. The final chapter summarises the findings of each experiment and considers the results in the context of previous literature. General limitations of the research and suggestions for future research are discussed.

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