Simply put, sexually explicit material triggers “mirror neurons” in the brain. These are the neurons involved in mimicking behavior and in the case of pornography, the mirror neuron system triggers arousal in the brain, which leads to growing sexual tension and a corresponding desire for release. The problem, according to Professor William M. Struthers, a psychologist at Wheaton College, is that “ … this leads to hormonal and neurological consequences, which bind [the man] to the object he is focusing on.” Pornography thus enslaves its users to its images in the sense that the biological response intended to bond a man and woman are transferred, thus loosening the bond between them and forming a bond with the pornography itself.
But this is only the beginning. In men, a primary chemical involved in sexual arousal which is affected by pornography use is dopamine, and it is well known that dopamine plays a major role in reward-driven learning. Many studies have shown that rewarded behaviors increase the level of dopamine transmission in the brain (the basis of addictions to drugs such as cocaine, amphetamine, and methamphetamine which act directly on the dopamine system). Dopamine production peaks in the brain when an individual is exposed to stimuli which are novel – especially if the stimuli are sexual. This is why pornography users become trapped in endlessly seeking new images – because they have trained themselves to be unsatisfied with the same stimulus.
As a result, viewing erotic images of numerous individuals can actually trigger more dopamine production than sex with an actual partner. In this way, pornography leads to a psychological addiction that teaches the brain that images are more satisfying – and the user becomes, in turn, less satisfied with his or her real partner (a process known to psychologists and ethnologists as the “Coolidge effect,” which affects mammalian males and to some extent females). With individuals not in sexual relationships the addiction is still firmly formed, and sexual relations within eventual marriage are doomed to prove less satisfying and less likely to hold the relationship together.
One of the final destructive effects of this cycle is that the overstimulation of the psychological reward process which occurs with repeated pornography-stimulated dopamine production creates actual desensitization; the brain doesn't respond as much as it used to do and the individual actually feels less reward from pleasure. Over time, that same desensitization causes porn users to have to work ever harder to accomplish feelings of satisfaction through more, more frequent, or more extreme sexual stimuli. The cycle is endlessly ongoing; and the more porn is used, the more numb the brain becomes.
Telling users that pornography debases or exploits women (although completely true) often has little effect because users are usually into porn for self-centered gratification which is elevated above the happiness of others; but porn users are themselves being harmed. A University of Sydney study found that those using porn regularly were more likely to have severe social and relationship problems and were more likely to lose their jobs, their relationships, and to get in trouble with the law. But if a user can understand what is actually happening to his or her “brain on porn,” it can help the person to realize that the happiness which is ultimately and most severely compromised by porn is their own.