Another weakness of the theory is how an infant has formed multiple attachment, is assessed.
Bowlby (1969) pointed out that children have playmates as well as attachment figures and may get distressed when they leave, but this does not signify attachment.
This undermines the multiple attachments stage because observation does not leave a way to distinguish between behaviour towards secondary attachment figures and playmates.
This suggests that the findings may not be a valid measure of multiple attachments.