This seems hugely misleading to me... "Free will" is not getting to choose right or left without warning. This is not even REAL "decision" making stuff. Free will would have been someone ripping that wired beanie off their head and saying. "This is a waste of my time and someone's money. I CHOOSE to leave. Did you see THAT coming??" or "Predict THIS!"
Also, they say the participant didn't know when the cue was coming so they couldn't prepare for it...the cue was at random intervals.... but the participant KNEW the cue would be coming at some point, so me thinks they could have prepared in advanced which way to move their eyes when the next cue showed up. No?
Someone's grasping at straws to discredit free-will.