Some people possess the ability to curl their tongue into a tube shape, while others cannot. This simple feat, known as tongue rolling, is a common human trait, with prevalence rates between 60% and 80% of the population. Understanding why some individuals can perform this unique maneuver involves exploring the structures of the tongue and the interplay of genetic and environmental factors.
The Anatomy of Tongue Rolling
The tongue is a flexible muscular organ, important for speech, swallowing, and taste. Its movements are controlled by two main groups of muscles: extrinsic and intrinsic. Extrinsic muscles originate from outside the tongue, attaching to surrounding bony structures like the hyoid bone, and move the tongue in and out or side to side. These muscles allow the tongue to protrude, retract, elevate, or depress.
Intrinsic muscles, conversely, are contained within the tongue. There are four paired intrinsic muscles: the superior longitudinal, inferior longitudinal, transverse, and vertical muscles. These muscles allow the tongue to change its shape and size for precise movements like articulation and food manipulation. Tongue rolling relies on the coordinated action of these intrinsic muscles, enabling the lateral edges of the tongue to curl upwards into a tube.
The Genetic Influence
For many years, the ability to roll one’s tongue was taught as a simple Mendelian dominant genetic trait. This theory suggested a single dominant gene determined the action. However, this simplified view has been largely disproven by scientific research.
Studies involving identical twins, who share nearly identical genetic material, have provided evidence against a simple genetic inheritance pattern. If tongue rolling were solely determined by a single dominant gene, identical twins would always either both possess the ability or both lack it. Yet, research has shown cases where one identical twin can roll their tongue while the other cannot, with discordance rates ranging from 18% to 28%. This indicates that while genetics does play a role, the inheritance is more complex, likely involving multiple genes (a polygenic trait) and other biological influences.
Can Tongue Rolling Be Learned?
Whether tongue rolling is a fixed genetic trait or a skill that can be acquired through practice is debated. While genetic predisposition is a factor, evidence suggests the ability can also be influenced by learning and development. The percentage of individuals who can roll their tongue increases with age, particularly during childhood.
For example, a study of Japanese schoolchildren noted that the proportion of tongue rollers increased from 54% among 6-7 year olds to 76% by age 12. This increase points to the role of muscle development and coordination over time. Some individuals who initially cannot roll their tongue may acquire the ability with practice, suggesting a learning component rather than an innate ability. However, even with practice, not everyone will be able to achieve tongue rolling, indicating that underlying physical or neurological factors still contribute to this ability.