I first encountered it in Robert Ornstein's book The Nature of Human Consciousness (http://www.amazon.com/exec/obidos/tg/detail/-/071670790X/qid=1113948587/sr=8-1/ref=pd_csp_1/103-0121261-5462208?v=glance&s=books&n=507846), which includes a reading on the investigation of the split-brain patients. The split-brain procedure (aka 'bisected brain' and 'callosectomy') severs the connections between the cerebral hemispheres, and is occasionally done in certain cases of severe epilepsy that don't respond to the usual treatments. It's a quite significant bit of brain tissue being cut, so they were surprised in the first trials to, at first, find minimal cognitive deficits. However, increasing investigation suggested that the hemispheres were functioning with remarkable independance -- which provided the situation for a number of clever cognitive experiments (as well as raising some interesting philosophical problems). The primary psychologists involved in these experiments where Michael S. Gazzaniga and H. W. Sperry. Gazzaniga's book The Bisected Brain (http://www.amazon.com/exec/obidos/tg/detail/-/030650040X/qid=1113948626/sr=1-1/ref=sr_1_1/103-0121261-5462208?v=glance&s=books) is a collection of reports on these experiments. The interpreter module (or 'left hemisphere interpreter' or 'left brain interpreter') was specifically his theory. Internet searches for these names and terms should produce a good bit of information.

Here are some articles by Gazzaniga on the topic: Automatic Brains -- Interpretive Minds (http://gnosia.tripod.com/gazz.pdf) (pdf) from Current Directions in Psychological Science, and The Split Brain Revisited (http://gnosia.tripod.com/gazz.htm) (htm) from Scientific American.