I think the ability to conceptualize is certainly an area where humans excel way beyond other animals. But I don't think that is central to the free will issue. For me, free will is the ability to delay automatic or instinctual response in order to modify behavior in a way that reflects prior learning. Apparently it is the frontal cortex that makes this possible and boy do we ever have a big one. But all mammals have it too to various degrees and many animals are able to learn.
The ability to conceptualize can widen the scope of perceived options but it is the mighty frontal cortex holding back the onslaught of instinctual response that makes it possible to act on those options.
The ability to conceptualize can widen the scope of perceived options but it is the mighty frontal cortex holding back the onslaught of instinctual response that makes it possible to act on those options.