Most courts agree tht there is no "unambiguous evidence"
that obscene materials cause increases in the number of
undesirable behaviours performed by consumers of the material.
Some of the research is too poorly done
to allow conclusions to be drawn from the results.
But even in the research that employs acceptable standards,
there are studies in which exposure to the materials
leads to increases in undesirable behaviours,
studies in which exposure
leads to decreases in undesirable behaviours,
and studies in which exposure has no measurable behavioural consequence.
However, there is no agreement about the circumstances
that determine whether exposure will cause an increase (activation),
cause a decrease (catharsis), or have no effect (null).
One would not want to facilitate exposure
in conditions in which exposure
increases the incidence of undesirable behaviours,
but one equally would not want to prevent exposure
under conditions in which the denial of exposure
increases the incidence of undesirable behaviours.