This is an interesting article about a dog, Mingo, who serves as a "co-therapist" with his owner, a psychologist. Every client is given the choice of having Mingo in the room during their psychotherapy sessions. Mingo is helpful to clients with a number of different types of problems: phobias, anxiety, depression, and more. Here's an excerpt that reminded me of what you wrote, Ipse Dixit:

http://www.gather.com/viewArticle.js...81474976729065
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Fifth, Mingo also becomes a "blank screen" onto which patients project thoughts and feelings of jealousy, deprivation, sibling rivalry and childhood hurts.... Some patients may even express jealousy of Mingo's having my love, thereby beginning to reveal experiences of feeling unloved by parents or believing that parents preferred a brother or sister over them.

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