[1] Nothofer (1986) presented lexical and phonological evidence in support of this subgroup, calling it "Barrier Islands–Batak".
Both Lafeber (1922) and Nothofer (1986) include Enggano as a probable daughter language.
[1][2] This is rejected by Edwards (2015) who considers Enggano a primary branch of the Malayo-Polynesian languages.
[3] Recent research by Smith (2017) however supports the inclusion of Enggano within his tentative "Sumatran" subgroup, which is an extended version of Northwest Sumatra–Barrier Islands that further includes the Nasal language spoken in Bengkulu in southwestern Sumatra.
[4] Smith's proposal is supported by Billings & McDonnell (2022) who classify the Sumatran languages as follows:[5] As phonological evidence for the inclusion of these languages with the Sumatran subgroup they propose:[5] Edwards (2015: 78)[3] provides the following table comparing body part vocabulary items across various languages of the Barrier Islands.