Virtual reality could spot real-world cognitive impairments: http://www.sciencedaily.com/releases/2012/11/121118141406.htm This is an article on a study involving stroke patients, but I thought it was interesting because it describes the problem where standard testing may not detect real world problems, implying there are no problems so the patient must be perceiving them (sound familiar?), but other tests may do a better job at detecting real-world problems. Cognitive impairment is established in CFS, although there is not always a correlation between self-reports and testing. This has lead some researchers such as the Nijmegen group eg Knoop et al to speculate that the perceptions of impairments are cognitive distortions which need correcting with CBT. One of their studies has shown that CBT can improve self-reported impairment but not actual test performance.