What sets humans apart from other animals? One primary difference is language; reading, writing, and speaking enable us to communicate with other people in different ways and express a huge range of thoughts and emotions. But we still have a lot to learn about the biological processes that govern those abilities. It's thought that genetics have a significant influence on such skills, particularly since studies with twins have suggested that anywhere from 30 to 80 percent of reading and writing abilities are heritable.
New research has assessed basic tests of reading and language, along with genetic data from thousands of people, and has revealed five reading- and language-related traits that are closely linked at the genetic level. The findings have been reported in the Proceedings of the National Academy of Sciences (PNAS). This study also did not come to the same conclusions as previous, smaller studies, suggesting that candidate genes that were identified in those reports may be false positives.
This work mostly involved English-speaking volunteers, although some were primary speakers of other languages including Finnish, French, German, Hungarian, and Spanish. The tests involved basic skills, such as reading real or made up words like horse, or 'chove.' In other tests, individuals were asked to say a word without one of the letters, such as pronouncing 'stop' but without the 's' or saying a spoonerism, in which a phrase such as 'nice day' is changed to 'dice nay.' Participants were also tested on verbal short-term memory, articulation, and speech perception by repeating nonwords of varying complexity, such as 'loddernapish.'
A genome-wide association study was performed to look for genetic variants that were linked to changes in language abilities. The ability to read words was linked to several genes on chromosome 1: DOCK7, ATG4C, ANGPTL3, and USP1. Some common genetic variants were identified in this study that have also been linked to verbal and nonverbal cognitive ability.
This research also found that there were individual differences that have a genetic connection in the neural anatomy of one region of the brain, called the left superior temporal sulcus. This region has an important relationship to spoken and written language, and appears to be crucial to spelling, reading, and phoneme awareness abilities. This study also showed that genetic differences underlying early brain development and the regulation of the fetal brain are related to reading and language abilities.
"If we can uncover the biological bases of skills involved in speaking and reading, we may learn more about how language evolved in our species," noted first study author Else Eising of the Max Planck Institute for Psycholinguistics (MPI) in Nijmegen. "In addition, we can better understand why there are individual differences in these skills, even in societies where most people receive similar high quality education towards literacy and language."