## 4 Discussion
### Limitations  
Although the current study was comprehensive, there remained inevitable limitations. It should be mentioned that the images which formed the \"erotic\" category obtained via the IAPS database may be seen as an outdated representation of erotica or pornography compared with what may be construed as \"average pornography\" which, in the modern era, is more expansive and visually stimulating. Future studies may need to utilise a more up-to-date standardised image database to account for changing cultures. Also, maybe high porn users downregulated their sexual responses during the study. This explanation was at least used by [7; 8] to describe their results which showed a weaker approach motivation indexed by smaller LPP (late positive potential) amplitude to erotic images by individuals reporting uncontrollable pornography use. LPP amplitudes have been shown to decrease upon intentional downregulation [62; 63]. Therefore, an inhibited LPP to erotic images may account for lack of significant effects found in the present study across groups for the \"erotic\" condition. This may be due to participants not being allowed to masturbate whilst watching pornographic (or in this case, erotic) images during the testing session, which is what they may do otherwise [64]. A further limitation of the current study was that the participant pool was divided into pornography use groups based on self-reported pornography usage. As studies based on physiology in this field of pornography consumption is relatively recent, there does not yet exist a set of physiological markers or a physiological profile which allows for a clear distinction between, say, a \"low\" or a \"high\" pornography use group. The obvious issue presented with this method may be due to some respondents' under-reporting or over-reporting their actual porn use. Further, the current study did not rely on a clinical sample with known and clinically diagnosed pornography use problems. The cohort used for the present study exists within a \"normal\" range with unproblematic porn use which may be termed not clinically significant and therefore may not have provided as robust a result as a comparison between clinically diagnosed and non-clinically diagnosed individuals. Furthermore, the effects noted in this paper differentiating between pornography use groups may indicate a correlation effect rather than causation. A link may be drawn here comparing individuals in the general population who consume alcohol. Both pornography consumption and alcohol use may be pleasurable and potentially damaging behaviours engaged in by many, but only a minority of individuals excessively participate in these behaviours to the point where it causes distress and associated adverse behavioural effects. It is entirely likely that our cohort was comprised of individuals who have not and will never suffer any sort of observable adverse behavioural effect due to their (excessive) use of pornography. The study of excessive pornography use is a relatively recent phenomenon, and there is a need to develop a standardised questionnaire used to explicitly measure pornography use and its associated conscious effects.