Humans have full 4D spatial vision Consider this: 1) objects in motion show non-simultaneities along the direction of motion (the "temporal distance" between the endpoints is [tex]\gamma vl/c^2[/tex]) 2) objects in motion show time dilation (the "temporal velocity" runs slow with a factor [tex]1/\gamma[/tex]) If our spatial vision would have been truly 3D: 1) implies that we would only see(*) a single point of the object with precisely the time-coordinate that coincides with ours. 2) implies that moving objects would vanish in the past alltogether. Those things obviously don't happen so we have full 4D spatial vision, i.e. we can observe all 4 dimensions in its entirety. (*) With "see" in this context I mean the usual "instant observation" of events as often used in relativistic thought experiments.