When put to a direct test, 
however, the claim that the 
Poggendorff effect is based on 
the overestimation of acute 
angles is found wanting. In the 
illustration to the left, the 
Poggendorff pattern is modified 
in two ways: In A, the acute 
angles are eliminated; in B, the 
obtuse angles are eliminated. As 
can be seen, the former 
continues to yield the illusion 
whereas the latter does not. 
Therefore, if misperception of 
angle accounts for the illusion, 
it must be argued that the effect 
occurs because obtuse angles 
are underestimated, not 
because acute angles are 
overestimated. However, this 
conclusion is not consonant 
with Blakemore et al.’s 
findings, nor does it follow 
from the lateral-inhibition 
theory.