By means of a large-scale web-based investigation, we established the degree of mutual intelligibility of 16 closely related spoken languages within the Germanic, Slavic and Romance language families in Europe. We first present the results of a selection of 1833 listeners representing the mutual intelligibility between young, educated Europeans from the same 16 countries where the test languages are spoken. Next, we present the data from a sub-group of listeners who had not learned the test language and had had minimal exposure to it. This allows us to investigate how well the listeners understand the test language on the basis of structural similarities between their own language and the test languages. Finally, we compare the results of the two data sets to the traditional genealogic characterisation of the three language groups. We expect the intelligibility results from the second group of listeners who had had minimal exposure to the test language to be a better reflection of the genealogical characterisation than the results from the larger group who had sometimes been exposed to the test language or had learned it at school