-Glaswegian infants. Sample lacks representativeness and cannot be generalised to infants in earlier attachments.
-It's a study of Western infants in individualistic cultures. In other cultures formation of multiple attachments earlier. Influence of communal childcare and not just one primary caregiver.
High in ecological validity
-Infants observed in their own homes. Attachments behaviours more natural than in a lab setting.
-Stages of attachment can be generalised.
Issues with validity
-Use of self-report, interviews.
-Possibility of social desirability bias in their response as want to show that they have a secure attachment with their child.
-This reduces validity of the research supporting stages of attachment.
