Older adult cohorts show greater external locus of control (LOC), a marker of social reliance, compared to younger cohorts. In the present study, American college students from 27 to 61 years of age participated in online courses in a graduate health science programme. Four birth-year cohorts were included: millennials, born in 1982+; generation X, born 1982–71; younger boomers, 1972–61; and older boomers, 1962–51. Pretest and posttest knowledge, digital nativism, self (internal LOC) versus social (external LOC) reliance and online activity were measured. Self versus social reliance was measured using Duttweiler's Internal Control Index, an adaptation of Rotter's Locus of Control. Millennial students were more likely to be digital natives, showed poorer knowledge application skill and were more self-reliant than older students. Older boomers represented the most socially-reliant learners, and were better at knowledge application, that is, answering questions that go ‘beyond the information given’. Older boomers were also more active in the websites associated with the online courses and were more likely to be digital immigrants rather than natives. Active participation, digital non-native status and social reliance contributed to better knowledge application. Instructors teaching millennial-age students need to encourage active, meaningful participation in applying knowledge.