First published in Cosmic Stories (March 1941 issue), by Isaac Asimov. The magazine issue has been uploaded as a digital copy on Fiction House Press, making it accessible as an ebook, too. This story is about a human who gains and loses the martian's ability to sense magnetic amplitude.
Lincoln Fields, a human from New York, is trying to demonstrate music to his friend, Garth Jan, an alien from Mars. Fields is trying to find art and beauty that his alien friend can enjoy. However, Garth simply doesn't have the same senses that humans do. As Fields pressures Garth, they blurt out that a human could be given the ability to directly sense electromagnetic fields, but only for five minutes.
Much later, Fields demands that Garth repay his hospitality by granting him the Martian sense. His friend complies, and arranges for a Martian concert, a portwem, to be played while he is able to hear/see it.
"The Secret Sense" provides examples of:
- Advertising by Association: When published in Cosmic Stories, this work referenced "Homo Sol" and "Trends" as previous stories by Dr Asimov.
- Alien Arts Are Appreciated: Despite trying his best, London can't get his Martian friend to appreciate human aesthetics. Frustrated with London's condensation, Garth points out that Earthmen can't appreciate Martian aesthetics either. (Unless they're given the Martian senses.)
- Beneath the Earth: Martian civilization exists as cities underneath the surface of the planet. Therefore, Earth couldn't see how technologically advanced its people were until they visited.
- Bizarre Alien Senses: These Martians are very sensitive to electric fields and able to see changing voltage and amplitudes, but have comparatively weak hearing and color vision. Humans have some of the same brain cells, and the Martians can stimulate those cell temporarily, but at the cost of losing the secret sense permanently.
- First Time Feeling: Lincoln Fields, a hedonistic rich kid, is excited to be given the Martian ability to sense magnetic fields by the voltage and amplitude. His friend has arranged for him to be present during a Martian portwem; basically a concert for this specific sense. When the five minutes are over, Fields is devastated.
- The Hedonist: Lincoln Fields has been rich since birth, and therefore has always been able to experience pleasure in nearly every conceivable form of art. When his Martian friend accidentally reveals the titular secret can be (briefly) gifted to humans, it doesn't take long before Lincoln demands to try it out and enjoy Martian artworks with Martian senses.
- Hour of Power: Martians can temporarily grant humans the ability to sense magnetic fields, but doing this once permanently burns out the part of the brain used, so it only lasts for five minutes.
- The Namesake: The titular sense is the ability of the aliens from Mars to sense the amplitude and intensity of magnetic fields. Most Martians keep it secret because they want to avoid torturing the recently-met humans via Sense Loss Sadness.
- Repeated for Emphasis: As Fields leaves the portwem, Garth calls out to rub in the Sense Loss Sadness Fields is feeling by emphasizing Fields feels blind now."You entered a normal man! You leave blind—blind-BLIND."
- Show Within a Show: The martians greatly respect portwem composer Bar Danin, and will play "Canals in the Desert" while the human character can perceive it.
- Super Empowering: Humans have an undeveloped organ in the brain that works like the Martian's sensory organ for magnetic fields. Martian medicine can stimulate the human version, making it work for five minutes, but it will never work again.
- Super Senses: Martians in this story have several senses that humans don't (and humans have better senses than martians). The most significant of their senses is that of detecting magnetic fields. They are able to grant this sense to humans, but only temporarily.
- Sense Loss Sadness: Garth predicts that having a sense only briefly would be a terrible torture, and compares it to someone going blind. When Lincoln finally stops sensing the portwem (a Martian concert/video created from sensing the shifting amplitude and and intensity of magnetic fields), his bewilderment gives way to crippling depression.The Earthman raised his head and grinned, but it was no more than a horrible baring of the teeth. It took every ounce of will-power he possessed to maintain an air of composure.
- Humans by Any Other Name: Several nouns are used for human beings in this work; human, Earthmen, and Terrestrial.