Adam Kolber (responding in part to a little prompting) has a post on Split Brains and Irrationality that replies to this post on Brains. Here is a taste of Kolber's post:
"Is it possible that our chronic irrational behavior may actually be driven by instincts" that the interpreter covers up with rational explanations? I think a lot of the recent work in neuroeconomics and behavioral economics indeed demonstrates that we often make decisions that are at odds with what a fully-informed, perfectly rational creature would do. I'm not sure what role "the interpreter" plays here and how precisely it is meant to connect with split-brain research. For one thing, I suspect that we often have no even-purportedly-rational story to tell ourselves (see, e.g., Jonathan Haidt et al.'s work on moral dumbfounding). Also, as for people with healthy human brains, we manage to give relatively good explanations of our behavior relative to those with so-called split brains. This suggests that any interpreter function derived solely from our understanding of split brains can only have limited applicability to those with healthy human brains.
K