limitation: conflicting evidence
point: findings vary according to methodology used
evidence: longitudinal studies (Grossman) suggest fathers have a distinct role (play and stim.)
-> suggests children growing up in single-mother/lesbian-parent families would turn out diff. to heterosexual families
explanation: this is a limitation as it means the question as to what role the father plays in attachment is unanswered
link: limitation - conflicting evidence b/c research has low validity + is useless