Peer mentoring programs usually target ethnic minorities, people with disabilities and women. This approach tends to be conceived out of the "deficiency model" where multi-ethnic students, women and students with disabilities are perceived as being in need of help and unlikely to succeed unless senior students or successful adults help them.[26] One of the main criticisms of peer mentoring is the lack of research to show how peer mentoring relationships work, how they develop, and what their outcomes are.[27] Also, the nature of being either a mentor or mentee and at the same time a peer can make the relationship a dual one where other identities also converge.[28] Some peer mentoring programs promote assimilation among ethnic minority students because of the use of student role models who are perceived as successful in social and educational environments characterized by majority students.[29] These role models then become the people that peer mentees strive to imitate or emulate.[30] A more subtle criticism of peer mentoring refers to their lack of supervision and structure: most peer mentoring programs led by undergraduate students rarely have direct supervision of full-time university staff.