Why notification sounds send you emotionally reeling into the past

It sounds like someone accidentally hit adjacent keys on a xylophone. The understated double ping hits me with a jolt of excitement, a swooping stomach, and even a bit of relief. Whenever I hear the now-retired Facebook Messenger notification, I'm transported back to 2013, when I happily, gratefully, giddily got a message from someone I liked, who would later become my partner. Back then, we talked almost daily on, of all chat platforms, Messenger. As devices, software applications, and apps bec...