It's relatively easy for human beings to think outside the box because we have so little instinctual box left.
Here's the bad side.
We have a powerful instinctive drive to fill the psychological hole where other species keep their instincts with a culture instead, and to bind ourselves to that culture as fiercely as though it were instinctive rather than learned. This is one of the main ingredients in the negative side of our flexibility, in which we can have a complete disregard for the truth because of our fanatical attachment to an arbitrary view of the world.
Unfortunately, the challenge for us is that we unthinkingly accept the assumptions and prejudices of our cultures with such tenacity that we often deny the existence of alternatives (or at least deny their right to exist). Psychologically, human culture is a form of monomania, of obsessions and compulsions orbiting a single idea or cluster of ideas we can't seem to escape, as though our adopted culture were biologically hard-wired.
Here's the good side.
Fortunately, the opportunity for us here is that biologically we don't care which culture we slavishly follow. Almost any conceivable culture, no matter how bizarre, will satisfy our craving. This is why we have created so very many different cultures throughout the world over time. In other words, we throw ourselves into our acting roles with unbridled conviction, but we're more or less as happy in one role as another.
In the absence of one instinctual box for all human beings, our species creates many different cultural boxes to replace that missing box.
This is a very, very good thing for our search for the truth, because it creates the opportunity for us to be jarred out of our cultural monomanias when we are shocked by exposure to other cultures. Magic happens to us in that crisis, because we acquire however briefly a glimpse of the essential human truth that our most beloved, cherished ideas and behaviors are not in fact God's own truth, merely an arbitrary choice imposed on us through the accident of our birth.
After all, from within the soap bubble of our own culture, no other culture seems desirable or perhaps even possible, and to us in our naivete that feels like the essential truth of both our culture and the world, so to see other human beings who not only successfully exist within an alien culture but are even happy and fulfilled within it creates an overwhelming problem for our worldview. Their existence simply cannot be reconciled with our worldview, and one of the two has to give.
When we resolve this crisis constructively, we begin to escape the box of our culture and create true personal freedom.