Motivations vary in the extent of their autonomy [14], defined as a sense of volition, self-initiation and personal endorsement of thought, a feeling or behaviour [15]. The self-determination theory (SDT) distinguishes four types of motivations on the basis of the
extent of their autonomy: (1) external regulation: a pressure
to think, feel or act in order to satisfy an external demand or
obtain an externally imposed reward, (2) introjected
regulation: a pressure to think, feel or act in order to satisfy
an internal demand or to avoid guilt or anxiety, (3)
identification: identification with the personal importance of
an action, and (4) integration: identified regulations have
been fully assimilated to the self. According to the SDT[14],
the more autonomous types of motivations (identification
and integration) are more likely to have a longer lasting
effect than other, less autonomous types of motivations
(external regulation and introjected regulation).