The apparently effective results of Operation Mockingbird would suggest that we (humans in general) can be influenced to think and act in ways that others want. Undoubtedly there are those that are manipulating us to do so.
This would hypothetically mean that we also have the ability to consciously create of our own free will. But I'm really not sure how a person would know to what degree a thought or action is influenced by external forces - either intentionally or unintentionally.