Their take-off point was an interest in observations made by Swiss psychologist Carl Gustav Jung, who described in the 1920s the temperamental differences of four psychological types.

他们的出发点是对瑞士心理学家卡尔·古斯塔夫·荣格 (Carl Gustav Jung) 的观察产生兴趣，荣格在 1920 年代描述了四种心理类型的气质差异。