The Paris Review on the creation of the laugh track:

Today’s sitcoms are based mostly on witty repartee and no longer rely on outlandish situations or sight gags, such as you would see in an episode of Mister Ed or The Munsters or Bewitched-and today’s muted laughs reflect that. Generally, laughs are now much less aggressive and more subdued; you no longer hear unbridled belly laughs or guffaws. It’s “intelligent” laughter-more genteel, more sophisticated. But definitely not as much fun. There was an optimism and carefree quality in those old laugh tracks. Today, the reactions are largely “droll”.