8

THE UPRIGHT WORLD
Observers floating in a gravity-
free space will still perceive 
the orientation of objects in 
relation to themselves.

If the retinal images of the 
scenes we view are upside 
down, why does the world not 
appear to be upside down as 
well? If an observer were 
floating in space far from 
Earth, so that the direction of 
gravity or other indicators of 
"up" and "down" in relation to 
the world were unknown and 
irrelevant, the question of the 
uprightness of vision from an 
inverted retinal image could 
still be posed. For if a second 
person were floating in space 
next to the observer, his or her 
image would be inverted on the 
observer’s retina, yet that 
person would not appear 
inverted.

    "Upright" and "inverted" are 
defined egocentrically here—–
that is, in terms of how things 
appear to be oriented in 
relation to the self. But there is 
another meaning of "upright" 
in perception. "Upright" can 
refer to the orientation of a 
thing in relation to the 
direction of gravity, to how it is 
positioned in the environment, 
quite apart from how it is 
oriented in relation to 
ourselves. No matter what may 
be our own body orientation, 
whether supine or even 
standing on our heads, we can 
still ask whether or not an 
object is perceived to be 
vertical or right side up in the 
world. In this sense, an object 
such as a tree may be perceived 
to be right side up even if we 
happen to view it when we 
ourselves are upside down, thus 
rendering it egocentrically 
inverted. Here, "upright" (or 
"tilted" or "inverted") is 
therefore defined 
environmentally. As will be 
seen, there are some intriguing 
problems to be addressed in 
understanding both the 
perception of an object’s 
environmental orientation and 
its egocentric orientation.