In the Season 8 episode "The Shot in the Dark", Brennan is shot while working in the lab late at night. While undergoing emergency surgery, she experiences a vision of meeting with her deceased mother, Christine Brennan. Initially dismissing this as a hallucination, Brennan experiences several more visions throughout the episode. During these discussions, it's revealed that Brennan's hyper rationalization originates from the very last piece of advice her mother gave to her (before going on the run) which was to use her brain instead of her heart. While that advice enabled Brennan to survive all these years, the vision of her mother explains, it's now time for Brennan to do more than just survive.