Bowlby proposed that a baby's initial attachment experience forms an internal working model, shaping future relationships. Secure attachments lead to functional relationships, while insecure attachments can result in relationship difficulties, being too uninvolved (insecure-avoidant) or controlling (insecure-resistant). Childhood friendships are influenced by attachment, with securely attached children forming better friendships and insecurely attached children facing challenges. Attachment type correlates with bullying behaviour, with secure children less likely to bully.