Lacks population validity
infants in the study all came from Glasgow and were mostly from working class families. In
addition, the small sample size of 60 families reduces the strength of the conclusion we can draw from the study.
cannot be generalised, and so is a limited explanation of attachment development.
Schaffer's stages of attachment lack both population validity and temporal validity -
parenting techniques have significantly changed since the 1950s, such as through the influence of Bowlby's work on attachment, and so caution should be taken when generalising the findings.