there is research into boding after the critical period, Hodges and Tizard (1989) - longditudinal study on children's homes before age 6 months, and were either adopted or went home to bio mother at the age of 4. Attachments were still made however were more impactful in the adoptive parents as they put in the added effort. showing that attachment can happen outside of the critical period. However there was still some behavioural effects such as age 15 finding hard to make friends, increase chance of being a bully