Less married or commited people view watching pornography as infedility, compared to the uncommited. Likely reason is the contact with reality once we are in a commited relationship

Is Viewing Sexually Explicit Material Cheating on Your Partner? A Comparison Between the United States and Spain. Charles Negy et al. Archives of Sexual Behavior, https://link.springer.com/article/10.1007/s10508-017-1125-z

Abstract: This cross-sectional study examined whether university students from the U.S. (n = 392) and Spain (n = 200) considered the viewing of sexually explicit material (SEM) to be tantamount to committing infidelity. Participants’ ages ranged from 18 to 36 (U.S. sample) and 18 to 35 (Spain sample), respectively. At both universities, the study was made available to students via a computer program that allows recruitment and completion of the questionnaires online. It was found that the majority of U.S. and Spanish participants (73 and 77%, respectively) indicated that they did not consider viewing SEM as an act of infidelity. Also, overall, U.S. participants, those who were not currently in a relationship, and those who do not view SEM, were significantly more likely to believe that viewing SEM constituted infidelity compared to Spanish participants, those currently in a relationship, and those who view SEM. Finally, it was found that among U.S. and Spanish participants, intolerance of infidelity in general, negative attitudes toward SEM, and the proclivity for jealousy significantly correlated with believing that viewing SEM was tantamount to infidelity. For U.S. participants only, religiosity and (low) self-esteem also correlated with the belief that viewing SEM was infidelity. Implications of the findings are discussed.