Gestalt psychology, school of psychology founded in the 20th century that provided the foundation for the modern study of perception. Gestalt theory emphasizes that the whole of anything is greater than its parts.

Transactional analysis (TA) is a therapeutic approach developed by Eric Berne in the 1950s. It has its roots in psychoanalysis, but maintains a focus on social transactions to determine ‘ego states’ in order to better understand behaviour (Berne, 1958, 1964). The International Transactional Analysis Association defines TA as a “theory of personality and a systematic psychotherapy for personal growth and personal change.”

Attachment Theory: Bowlby’s evolutionary theory of attachment suggests that children come into the world biologically pre-programmed to form attachments with others, because this will help them to survive. A child has an innate (i.e. inborn) need to attach to one main attachment figure. This is called monotropy. This concept of monotropy suggests that there is one relationship which is more important than all the rest.

Carl Jung : Like Freud (and Erikson) Jung regarded the psyche as made up of a number of separate but interacting systems. The three main ones were the ego, the personal unconscious, and the collective unconscious. According to Jung, the ego represents the conscious mind as it comprises the thoughts, memories, and emotions a person is aware of. The ego is largely responsible for feelings of identity and continuity.

Carl Rogers (1902-1987) was a humanistic psychologist , he added that for a person to "grow", they need an environment that provides them with genuineness (openness and self-disclosure), acceptance (being seen with unconditional positive regard), and empathy (being listened to and understood).