I can give you a good EEG story, told to me by an engineering professor who was studying EEG data back in the 70s:
Some researchers set up an EEG hooked up to a computer that could display some analysis to the user (basically magnitudes of various waves). The idea was to see if biofeedback (people trying to control their EEG output in realtime) could lead to any benefits. All they got was positive feedback (no pun intended): people would tell them how it helped them focus, relax, think clearly, etc. Then at some point, one of the researchers realized a cable was unplugged and the values shown to people were just random noise...
Some researchers set up an EEG hooked up to a computer that could display some analysis to the user (basically magnitudes of various waves). The idea was to see if biofeedback (people trying to control their EEG output in realtime) could lead to any benefits. All they got was positive feedback (no pun intended): people would tell them how it helped them focus, relax, think clearly, etc. Then at some point, one of the researchers realized a cable was unplugged and the values shown to people were just random noise...