I think this is a key to understanding not only how we think but also how we learn: "there is no real categorical difference between imagination and reality, but that they are subjectively intermixed. When this combination of internal and external signals is strong enough, we believe it reflects reality." The second key (not in the article) is that we don't intentionally create these signals, nbeither external nor internal. We don't 'construct' our understanding of reality. Rather, we grow into it through a process of, as Hume would say, custom and habit.