During the middle of the 20th century, the linguist Robert John Gregg established the geographical boundaries of Ulster's Scots-speaking areas based on information gathered from native speakers. By his definition, Ulster Scots is spoken in mid and east Antrim, north Down, north-east County Londonderry, and in the fishing villages of the Mourne coast. It is also spoken in the Laggan district and parts of the Finn Valley in east Donegal and in the south of Inishowen in north Donegal. Writing in 2020, the Fintona-born linguist Warren Maguire argued that some of the criteria that Gregg used as distinctive of Ulster Scots are common in south-west Tyrone and were found in other sites across Northern Ireland investigated by the Linguistic Survey of Scotland.