The device does not reproduce normal human vision, but does allow the character to "see" energy phenomena visible to the naked human eye while expanding the wearer's full perceived spectrum to 1 Hz — 100 PHz. This also allowed the character to see human vital signs such as heart rate and temperature, giving him the ability to monitor moods and even detect lies in humans (but not aliens). In the episode Heart of Glory, Captain Picard keys the main viewer to Geordi's visor allowing him to see the way he does. Seeing all the overlapping and different wavelengths was highly confusing to the Captain, prompting him to ask Geordi how he was able to differentiate between them all. Geordi's response made the comparison of a child hearing many different sounds at once and eventually being able to pick out what they needed; it is a learned talent.