Stress is reduced when the burden is shared between kerbals of the same specialty on a vessel. The formula can be simple X / N or may be more complicated (taking into consideration their experience, training level etc.).
This should not apply to Tourists, for obvious reasons.
The point is to:
incentivize having more than one kerbal of a specific profession on a mission
give the player a way to reduce Stress to, theoretically, as low as needed (of course, the tradeoff is the need to provide Living Space for the kerbals)
Stress is reduced when the burden is shared between kerbals of the same specialty on a vessel. The formula can be simple X / N or may be more complicated (taking into consideration their experience, training level etc.).
This should not apply to Tourists, for obvious reasons.
The point is to: