Using data from 4,644 undergraduates, this study tested a causal model identifying effects of social integration, age, and time limiting characteristics on adult student learning. Time limiting characteristics included such constraints as off-campus responsibilities and relationships. Educationally related peer relationships were the strongest predictors of gains for all students. Time-limitations hindered learning for younger students, but not for students aged 30 and older. (Contains 1 figure, 3 tables, and 28 references.) (Author/SLD)