First author of the study Stephen Fleming, from University College London Institute of Neurology, observed that our internal choices stand to face reversal when we are told by the outside world which choice to make.
Using EEG (electroencephalogram), experts recorded the brain activity of the research partakers, who had been asked to select one out of two buttons.
While some chose freely, others responded to a subsequent signal asking them to change their minds after they had made their decision, but before hitting the button.
Fleming said: "When people had chosen for themselves which action to make, we found that the brain activity involved in changing one's mind, or reprogramming these 'free' choices was weak, relative to reprogramming of choices that were dictated by an external stimulus.
"This suggests that the brain is very flexible when changing a free choice - rather like a spinning coin, a small nudge can push it one way or the other very easily.
"The implication is that, despite our feelings of being in control, our own internal choices are flexible compared to those driven by external stimuli, such as a braking in response to a traffic light. This flexibility might be important - in a dynamic world, we need to be able to change our plans when necessary."
Professor Patrick Haggard, UCL Institute of Cognitive Neuroscience, added: "We often think about our own internal decisions as having the strength of conviction, but our results suggest that the brain is smart enough to make us flexible about what we want.
"The ability to flexibly adjust our decisions about what we do in the current situation is a major component of intelligence, and has a clear survival value."
The study was published in Cerebral Cortex. (ANI)