Who predicted?

To examine the effect this widespread use of porn may be having on society, researchers have often exposed people to porn and measured some variable such as changes in attitude or predicted hypothetical behaviors
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To examine the effect this widespread use of porn may be having on society, researchers have often exposed people to porn and the researchers measured some variable such as changes in attitude or the researchers predicted hypothetical behaviors ?

Context:

To examine the effect this widespread use of porn may be having on society, researchers have often exposed people to porn and measured some variable such as changes in attitude or predicted hypothetical behaviors, interviewed sex offenders about their experience with pornography, and interviewed victims of sex abuse to evaluate if pornography was involved in the assault. Surprisingly few studies have linked the availability of porn in any society with antisocial behaviors or sex crimes. Among those studies none have found a causal relationship and very few have even found one positive correlation.