Merriam-Webster defines pornography as the depiction of erotic behaviour intended to cause sexual excitement. A similar definition is used in psychology, including “images of exposed genitals and/or depictions of sexual behaviours” that “is intended to increase sexual arousal” (Morgan, 2011).
However, some researchers include media that show only nudity with no sexual contact in their definition while others exclude any media that doesn’t show sexual acts or aroused genitals. Others still include all sexually explicit materials regardless of intention to arouse (Mckee et al., 2020).
This lack of clearly defined parameters has led to the subjective "I know it when I see it" definition of pornography. This was U.S. Supreme Court Justice Potter Stewart’s mentality when describing hard-core pornography in 1964, stating “I shall not today attempt further to define the kinds of material I understand to be embraced within that shorthand description, and perhaps I could never succeed in intelligibly doing so. But I know it when I see it, and the motion picture involved in this case is not that.”
Troublingly, pornography researchers use arbitrary definitional decisions that vary dramatically from person to person. This lack of a clear and comprehensive understanding of pornographic content is not conducive for productive research.
For example, one study says that 88% of pornography is violent (Bridges et al., 2010) while another says 13% is (Gorman et al., 2010). This discrepancy is partly due to researchers’ differences in interpreting aggressive acts as being non-consensual (McKee, 2015).
Also, consider the following image from psychologist Taylor Kohut’s Porn Genome project.
Generally, people see the image on the right with the red masking as more pornographic than image on the left. This is intuitive because you can’t see her clothes but is also counter-intuitive when you take into account that there is significantly less skin exposed.
None of the methods that are currently available for classifying pornography properly account for both the presence and the absence of visual cues that people use when making such judgments.