Infant observation has long been considered an important training exercise for child psychotherapists and for psychoanalysts (Bick, 1964). This has led to certain theoretical developments commonly associated with the work of Esther Bick (1968, 1986).

Bick began this work in 1948, shortly after Melanie Klein had described the paranoid-schizoid position. In Klein's view of the paranoid-schizoid position, the ego has a primary sense of a boundary between itself and the external world. Bick described a variant of this process, in which boundary of the ego is not primary, but comes from the sensations arising from skin contact. Sufficient skin sensations are necessary to give the experience of a boundary.

One of the processes she noticed interpersonally was that the breaking of skin contact appeared to be experienced by the infant as a hole from which it could leak. She noticed the frequency with which infants become incontinent...