There is a lot of experiments that materialist's use to support their view that free will is illusory. These experiments however are often misinterpreted to support that view. There are three big reasons why the experiments don't provide that free will is illusory. This is taken from brain blogger all credit goes to W.R. Klemm, DVM, PhD. (I realize he isn't a dualist but he makes good points when it comes to free will not being illusory based on experiments purported to show it. So here we go.
1. The timing of a free will event requires introspection as well as other research hows that introspection estimates of event timing are not accurate.
2) Simple finger movements may be performed without much conscious thought and certainly not representative of the conscious decisions and choices required in high-speed conversation or situations where the subconscious mind cannot know ahead of time what to do.
3) The brain activity measures have been primitive and incomplete.
There are some more obvious issues as well that many scientist's have glossed over when examining the data.
Decisions are not often instantaneous (certainly not on a scale of a fraction of a second).
Conscious realization that a decision has been made is delayed from the actual decision, and these may be two distinct processes.
Decision making is not the only mental process going on in such tasks.
Some willed action, as when first learning to play a musical instrument or touch type must be freely willed because the subconscious mind cannot know ahead of time what to do.
Free-will experiments have relied too much on awareness of actions and time estimation of accuracy.
Extrapolating from such simple experiments to all mental life is not justified.
Conflicting data and interpretations have been ignored.
We should not underestimate the true power of the subconscious mind, and it is the subconscious mind that shares duties with the conscious mind. This have been known for decades from research done in psychical research and parapsychology.