Carl Jung was the first psychologist to attach importance to tarot symbols. He may have regarded the tarot cards as representing archetypes: fundamental types of person or situation embedded in the subconscious of all human beings. The Emperor, for example, represents the ultimate patriarch or father figure.The theory of archetypes gives rise to psychological uses. Because the cards represent this different types of people, ideas of the subject's self-perception can be gained by asking them to select a card that they 'identify with'.
Equally, the subject can try and clarify the situation by imagining it in terms of the archetypal ideas associated with the card. For example, someone rushing in heedlessly like the Knight of Swords, or blindly keeping the world at bay like the Rider Waite Smith Two of Swords.
The Tarot has been said to be a kind of language of the "subconscious" , allowing it to be analyzed at the conscious level. Like many "New Age" therapies, however, tarot cards are not used by psychologists.
Although Jung and Freud are still seen as important innovators, the majority of psychologists today are still quite critical of many aspects of their theories.
There are no known university programs that teach this practice and there is no empirical evidence of therapeutic use or benefit. There are also no scientific papers published on their use in any professional journals.
More recently Dr Timothy Leary has suggested that the Tarot Trump cards are a pictorial representation of human developement from a baby to a fully grown adult. The Fool symbolising the new born infant, The Magician symbolising the stage at which an infant starts to play with artefacts etc.
In addition to this Dr Leary also considers the Tarot Trumps to be a blue print for evolution in general and that the latter half of the major arcana represent the future evolution of humans. Your can explore his ideas in his book "The Game of Life" which explains each of the Tarot Trumps in psychological developmental language.