Critical period – This is the time in which an attachment can form i.e. up to 2.5 to 3 years old. Bowlby suggested that if an attachment is not formed in this time, it never will. If an attachment does not form, you will be socially, emotionally, intellectually and physically stunted. Bowlby demonstrated this in his 44 juvenile thieves study, where maternal deprivation was associated with affectionless psychopathy and mental retardation.