I have always understood Stapp's scheme to be that the mind influences the brain by observing the state of some quantum variables. Say you measure something and find it is in a particular eigenstate: |1>. Since the system is not completely isolated (being in a blood-temperature brain!), this state will drift over time by interactions. However, if you keep observing the variable often enough, you can make the probability of a drift as small as possible. Say the state gets slightly mixed: (|1>+a|2>)/Sqrt(1+a^2) where a would increase roughly linearly with time. If you measure the state again you have a probability 1/Sqrt(1+a^2) which is approx 1-(a^2)/2 that it will still be in state |1>. This means that by choosing to measure it over and over again, you can make the probability of drift to another state as small as you like.
Thus, according to Stapp, observation can affect the system because you decide what to measure and how often.
I may be talking total BS here, but that has always been my understanding.
David  |