Because the objection of 
Boring and others could be met 
in this way, and because 
Boring’s own theory was 
implausible, it seemed proper to 
reopen the investigation of the 
taking-into-account theory as 
an explanation of the moon 
illusion. In the early 1960s, 
Lloyd Kaufman and I developed 
a set of experiments to test this 
theory. The basic idea behind 
our initial experiments was 
quite simple, namely to create 
artificial moons that, optically 
speaking, would be far away 
from the observer, just as the 
real moon is. To make 
immediate comparison 
possible, and thus avoid the 
possible inexactitude caused by 
the long delay typical in 
observing the moon in its 
different celestial locations 
under natural conditions, we 
created two such artificial 
moons. To make measurement 
of the illusion possible, we 
designed the disk of light 
simulating a moon so that its 
size could be varied.