Mutual intelligibility between Danish and the other two Scandinavian languages has declined over the 20th century. Danish has undergone some striking phonological developments (compare modern pronunciation to that of reference works written before the war) that have made it extremely difficult for Norwegians and, even more, Swedes to understand Danish without prior experience with the language. Nina Grønnum's 2003 paper titled “Why are the Danes so hard to understand?" looks at some of these quirks in detail.

It is interesting to attend international events and watch the Scandinavians in their 60s or 70s speak among each other in their own languages with seemingly no problem, since their generation was pushed to overcome any hurdles to understanding the neighbours, while a group of younger Scandinavians that includes Danes is likely to switch to English because it just feels easier.