Early handwriting style has both genetic and environmental origins

Handwriting is a ubiquitous physical trace of human behaviour. It is individual to a particular writer, even among twins (Srihari et al. 2008). We rely on the stability and distinctness of handwriting style to establish the... [ view full abstract ]

Handwriting is a ubiquitous physical trace of human behaviour. It is individual to a particular writer, even among twins (Srihari et al. 2008). We rely on the stability and distinctness of handwriting style to establish the validity of legal documents and to convict individuals of crimes. However, although we know much about the genetic and environmental origins of traits such as reading, language ability and spelling, we know little about the origins of writing, and nothing to date about the aetiology of handwriting style.

Previous research has shown that teacher-rated writing ability has both genetic and environmental influences (Kovas et al., 2007), as do tests of writing ability such as creative sentence construction, writing fluency and handwriting speed (Olson et al., 2013). However, the complexity of handwriting style makes it difficult to study in a quantitative way.

We used a novel machine learning approach (Newell & Griffin, 2014) to encode and compare handwriting samples from 4,349 seven-year-old twins from the UK’s Twins Early Development Study (TEDS). Structural equation modelling of the twin data showed statistically significant genetic (8%), shared (65%) and non-shared (26%) environmental influence on handwriting style, with no apparent aetiological sex differences.

Srihari, S., Huang, C. & Srinivasan, H., 2008. On the discriminability of the handwriting of twins. Journal of Forensic Sciences, 53(2), pp.430–446.

Kovas, Y., Haworth, C. M. A., Dale, P. S. & Plomin, R., 2007. The genetic and environmental origins of learning abilities and disabilities in the early school years. Monogr Soc Res Child Dev 72(vii), pp.1–144.

Olson, R.K. et al., 2013. Genetic and environmental influences on writing and their relations to language and reading. Annals of dyslexia, 63(1), pp.25–43.

Newell, A.J. & Griffin, L.D., 2014. Writer identification using oriented Basic Image Features and the Delta encoding. Pattern Recognition, 47(6), pp.2255–2265