Funny. One measure when motor signal and sees that it can measure when it appears in consciousness. Do me a favor, how can you be sure that what you measure is actually consciousness. Give me a "measurable" consciousness.
Moreover, Freud basically says that free will doesn't exist because he makes a difference between conscious and subconscious... The latter being a huge bunch of thoughts you don't make/change at will...
Moreover, predicting if a ball will fall when put above the ground is something. Predicting the next second of life of the universe is something else. So predicting a subject will raise its left/right hand is something. Predicting what will be his opinion about abortion is an entire story
All of this reminds me of studies done long ago which tried to predict if someone was a criminal or not by measuring the shape of its skull...