Abstract A fundamental question of complexity theory is the direct
product question. A famous example is Yao

s XOR-lemma, in which one
assumes that some function
f is hard on average for small circuits (meaning
that every circuit of some fixed size
s which attempts to compute
f
is wrong on a non-negligible fraction of the inputs) and concludes that
every circuit of size
s
only has a small advantage over guessing randomly
when computing

on independently chosen

. All known proofs of this lemma have the property
that
s
<
s
. In words, the circuit which attempts to compute

is
smaller than the circuit which attempts to compute
f on a single input!
This paper addresses the issue of proving
strong direct product assertions,
that is, ones in which

and is in particular
larger than
s.
We study the question of proving strong direct product question for decision trees and communication protocols.