:( Lacks cultural relativism
> Most of the research is carried out in Western cultures (individualistic).
> Relationships in these cultures are generally voluntary and often come to an end (divorce).
> However, relationships in collectivist cultures are more likely to be compulsory, less easy to end, and involve wider family.
> This suggests that Duck’s phase model of relationship breakdown is not applicable to all relationships across all cultures due to their different norms and values, lowering the external validity of the theory