A weakness of Ainsworth's strange situation?

-Classification system of attachment is incomplete -Main and Solomon conducted subsequent reserach whereby they anaylsed severl hundred strange situation epidsodes via videotape and suggested that Ainsworth overlooked a 4th types. It was noted that some infnats showed inconsistent patterns of behaviour, which they termed Type D - Insecure-disorganised -Futhur support for this claim comes from a meta-analysis of studies from the Us conducted by Van Ijzendoorn et al, found that 15% of infants were in fact, classified as type D -On balance, it's clear that Ainsworth behaviour cateforeis used for classification require updating in the face of this evidence to ensure high internal validity.