Despite these results, the 
familiar-size cue may be more 
an intellectual judgment than a 
genuine perceptual cue to 
distance. One can figure out 
that a playing card that looms 
so large in one’s field of view 
must be rather near. But that 
does not necessarily mean that 
it is perceived as near. 
Furthermore, it is unlikely that 
familiar size is a distance cue 
of much importance in daily 
life, when other cues are 
available. Experiments on this 
question are inconclusive. If 
we view an object of abnormal 
size under natural conditions, 
such as a dollhouse among a 
row of suburban homes, for 
example, we immediately 
detect its abnormality rather 
than reevaluate its distance or 
that of nearby homes.

Many textbooks also mention 
"height in the field" as a 
pictorial cue, but the argument 
used to support it is circular. 
Ordinarily, the farther away an 
object is, the higher will be its 
image in a picture or its 
projection to the eye. But this is 
true only for objects that rest 
on the ground, so that "height"
could be a cue to depth only if 
the observer already perceived 
a ground plane, which, by 
definition, recedes into the 
distance. Even if the argument 
were not circular, "height in 
the field" would be an 
ambiguous cue to depth because 
the lower the location of an 
object is in a plane overhead, 
such as a cloudy sky or ceiling, 
the farther away it is.