In an experiment in 1986, he recruited 42 men and assessed them on the "likelihood of rape" scale. Then he divided them randomly into three groups. The first was given a selection of sexually explicit materials containing scenes of rape and sadomasochism. The second was given non-violent pornography. The third group - the control - was given none at all.
About a week later, in what they thought was an unrelated experiment, each of the men was paired up with a woman, and told that she was not attracted to him. Then they had to play a guessing game, with the man having an option to punish the woman each time she got the answer wrong.
From this and many other experiments, Malamuth concluded that if a man is already sexually aggressive and consumes a lot of sexually aggressive pornography, there is a greater likelihood that he will commit a sexually aggressive act.
He draws an analogy with alcohol.
"For some people alcohol simply has the effect of making them more relaxed, letting them have more fun. For other people it's true that alcohol can increase the likelihood that somebody will behave in a violent way.
"But if I simply make the overall generalisation alcohol causes violence or leads to violence, you'd probably say that's glossing over a lot of the nuances.