On the rare occasions that Bill Shatner has publicly interacted with his own hair, usually by stroking it, he has unwittingly revealed what our toupologists have labeled the "Real Hair Reflex". This means that Shats, when touching his hair is both consciously and subconsciously inclined to only stroke the parts that are real.
This reflex serves two purposes: 1. - it preserves the tactile sensory experience of interacting with a living and true part of your being rather than a toupee 2.- it avoids the unwelcome possibility of displacing or otherwise unnecessarily interfering with the placement of the toup. A possible third motivation is to subtly smooth down the lower rear edge of the toup.
Below is an example from Bill Shatner's appearance on The Mike Douglas Show on the 25th February 1969, shortly after the final Star Trek episode was filmed. Mike Douglas also seems to be wearing a hairpiece.
The full sequence, which involves another hair stroke by Shats can be seen below:
We'll have a few more examples of the "Real Hair Reflex" soon.