For example, in an Iowa study, a group of sex offenders subject to registry requirement ( n = 233 ) who were also under legal supervision were compared to a matched group of preregistry sex offenders not under supervision ( n = 201 ).
12.
There are only 2 ways to determine causality neither of which seems likely to be undertaken with respect to health risks and porn : 1 ) Have two matched groups, in which one group uses porn and the other does not . 2 ) Remove porn for an extended period and see the results.
13.
A study by Block and Ghoneim ( 2000 ) found that, relative to a matched group of healthy, non-drug-using controls, heavy marijuana use is associated with small but significant impairments in memory retrieval . cannabis induces loss of internal control and cognitive impairment, especially impairment of attention and memory, for the duration of the intoxication period.
