TV URBAN LEGEND: Concerns over the depiction of hypnosis led to the creation of the Vulcan mind-meld.
Looking back, it was fascinating how some of the most iconic aspects of Star Trek history were more or less made up as they went along, while also noting the often bizarre ways that decisions were made about who would be in a particular episode.
For instance, Mister Spock's famous Vulcan nerve pinch was introduced when Leonard Nimoy did not like that the original script for the episode had him knocking Captain Kirk out (he felt it was too violent for Spock). So Nimoy pitched them the Vulcan nerve pinch, they accepted it and voila, an instant piece of Star Trek history!
Just a few episodes later, a similar piece of improvisation was used for the creation of the famous Vulcan mind-meld.
In "Dagger of the Mind," Kirk and the Enterprise's ship psychiatrist (her role was originally intended for Grace Lee Whitney's Ensign Rand, but then the producers did not want to get Kirk and Rand romantically involved, and since the role called a romance plot, they came up with a different character for the episode, Dr. Helen Noel) visit a planet where the mentally insane are kept. However, Dr. Simon van Gelder, one of the assistants to the renowned doctor who runs the asylum tricks his way on to the Enterprise, where he appears most unstable.
They have to find a way to communicate with him, as he was implying that Kirk and Noel, still on the planet below, were in some sort of danger.
The original script by Shimon Wincelberg (using the pen-name S. Bar-David) called for the crew to use an "Alien hypnosis" on van Gelder to learn what his deal was.
This caused a problem, because the network had some strict rules on hypnosis.
From the network in 1966:
In accordance with our precautions to avoid hypnotizing a viewer, the act of hypnotizing must be either out of context or done off-camera. Further, since you are portraying hypnotism as a legitimate medical tool, Van Gelder should be hypnotized by Dr. McCoy rather than Mr. Spock unless Mr. Spock can be established as being qualified in the use of this technique.
So yes, they were seriously afraid that a particularly susceptibly member of the audience at home would be hypnotized!!
The show considered having Dr. Leonard McCoy come in to do the hypnosis. Another alternative was to reveal that, "Oh, wait, you didn't know? Spock is a licensed hypnotherapist!"
However, since they were already building up Spock's back story and his cultural heritage as a Vulcan, they came up with the solution that Vulcans had the ability to perform "mind-melds" (which is not hypnosis, since Spock specifically explains that it is is not hypnosis, telling McCoy, “This will not affect you, Dr. McCoy, only the person I touch. It is not hypnosis") and thus Spock performed one on van Gelder to get the required information (although he expressed some temerity in doing so, noting "It's a hidden, personal thing to the Vulcan people, part of our private lives." He would soon be doing them constantly)...
Spock learned the truth (that the respected Dr. Adams who ran the asylum was using a special machine to take control of everyone's minds! He even made Kirk fall in love with Dr. Noel...
Granted, this was Kirk, so that was not too tough).
They eventually rescued Kirk and Noel (after Noel first disabled the shields blocking the Enterprise from teleporting to the planet's surface) and van Gelder (whose sanity was restored by the mind-meld) was named the new head of the asylum.
The legend is...
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