Lucy did as she was told and awkwardly snaked her hands in to keep the indicated crystals in the proper place. She had absolutely no idea what his technobabble meant and she didn't ask. More than likely "psychic energy" was a fancy term for "Christmas cheer". The idea that you could track such a thing struck her as faintly ludicrous and again she thought the Doctor silly for even trying.

But she was subject to his whims so there was no point in grousing overlong about it. She watched as he whacked the gadget and tried to keep the crystals steady.