The Gestalt principle of good 
continuation has recently 
received experimental support 
that makes at least one aspect 
of it more precise and objective. 
Philip Kellman and Thomas 
Shipley at Swarthmore College 
investigated the conditions 
that lead to the perception that 
stimulus patterns on either 
side of an occluding object (as 
in the tree example) belong 
together, and have advanced a 
mathematical formula that 
predicts the perceptual 
outcome.

    Two other important 
principles of organization are 
proximity and similarity. Other 
things being equal, we tend to 
organize units that are closest 
together as parts of an overall 
whole. Thus, we perceive the 
string XXX XXX XXX XXX as a 
set of four triplets of Xs. We 
could just as well describe them 
as six sets of pairs of Xs, but the 
differences in spacing favors 
the former perception. 
Proximity is, of course, 
relative. Thus, the separations 
that are the greater in one 
array of units, and therefore do 
not lead to groupings, may 
become the lesser in another 
array and thus lead to 
groupings.