  We compare the general effective theory of one-body dark matter nucleon
interactions to current direct detection experiments in a global
multidimensional statistical analysis. We derive exclusion limits on the 28
isoscalar and isovector coupling constants of the theory, and show that current
data place interesting constraints on dark matter-nucleon interaction operators
usually neglected in this context. We characterize the interference patterns
that can arise in dark matter direct detection from pairs of dark
matter-nucleon interaction operators, or from isoscalar and isovector
components of the same operator. We find that commonly neglected destructive
interference effects weaken standard direct detection exclusion limits by up to
one order of magnitude in the coupling constants.
