The block sensitivity of a Boolean function 
at an input 
is the largest number of pairwise disjoint sets of coordinates 
, each nonempty, such that 
for every 
, where 
reverses the coordinates in 
. The block sensitivity of 
is 
(Virza 2010).
Blocks consisting of singleton sets show that 
, where 
is Boolean function
sensitivity. For example, the disjunction of
inputs has both quantities equal to 
at the all-zero input. The sensitivity
conjecture concerns a bound on block sensitivity that is polynomial in 
.
The quadratic bound in terms of spectral sensitivity has a reported counterexample (Meiburg 2026).
