Originally, our brains were designed to be multilingual, managing two or more languages easily. Neuroscientist Thomas Bak (University of Edinburgh) reckons that, like sedentary lifestyles and an unhealthy diet, the monolingualism thats come with modern society has its consequences. Research has shown that speaking only one language makes our thinking skills decline faster as we age and can actually make us more vulnerable to dementia in later life. So why arent public health campaigns addressing this? Should Fitbits be monitoring our speech as well as our steps?