I'd suggest that the advocacy organizations making these unusual claims bear the burden of backing it up with evidence to support it. I'd be inclined to ask them why they believe this to be true.

From what little I know of this area of research, I understand that there are distinct effects for violent versus non-violent pornography, with only the former showing associations with decreased empathy. I've not heard anything to suggest that any type of pornography is a "gateway porn" to child pornography use.

Well, yes, there are distinct effects for violent versus nonviolent pornography.  Violent pornography has more damaging effects than nonviolent; however, nonviolent still has many documented harms.  It is almost a moot question lately though given the research by Bridges and others showing that nearly all available porn these days is violent.

Could you point me to a good review or key paper in the Bridges et al. research you referenced? I'm not familiar with it.

Even if we were to say that all pornography these days is violent and has many documented harms, I still find the claim that it leads to a devolution towards child pornography remarkable (and new to me). Of course those asserting this claim bear the burden of proof. I'll be interested to see if this thread turns up some support.

Here are some good references, including Bridges.

 Boies, S. C. (2002). University students’ uses of and reactions to online sexual information and entertainment: Links to online and offline sexual behavior. The Canadian Journal of Human Sexuality, 11 (2), 77–89.

Braun-Courville, D.K. & Rojas, M. (2009). Exposure to sexually explicit web sites and adolescent sexual attitudes and behaviors. Journal of Adolescent Health, 45, 156–162.

Bridges, A.J., Wosnitzer, R., Scharrer, E. Sun, C., & Liberman, R. (2010). Aggression and sexual behavior in best-selling pornography videos: A content analysis update. Violence Against Women, 16, 1065-1085.

Brosi, M. W., Foubert, J.D., Bannon, R.S., & Yandell, G. (2011). Effects of women’s pornography use on bystander intervention in a sexual assault situation and rape myth acceptance. Oracle: The Research Journal of the Association of Fraternity/ Sorority Advisors, 6(2), 26-35.

Brown, J.D. & Engle, K.L. (2009). X-Rated: Sexual attitudes and behaviors associated with U.S. early adolescents’ exposure to sexually explicit media. Communication Research, 36(1), 129-151.

Carr, J. L. & VanDeusen, K. M. (2004). Risk factors for male sexual aggression on college campuses. Journal of Family Violence, 19 (5), 279-289.

Carroll, J. S., Padilla-Walker, L. M., Nelson, L. J., Olsen, C. D., McNamara B. C., & Madsen, S. D. (2008). Generation XXX: Pornography acceptance and use among emerging adults. Journal of Adolescent Research, 23(1), 6-30.

Cavaglion, G. & Rashty, E. (2010). Narratives of suffering among Italian female partners of cybsersex and cyber-porn dependents. Sexual Addiction and Compulsivity, 17, 270-287.

Cooper, A., Delmonico, D.L., Griffin-Shelley, E., Mathy, R.M. (2004). Online sexual activity: An examination of potentially problematic behaviors. Sexual Addiction & Compulsivity, 11, 129-143.

Davis, K.C., Norris, J., George, W.H., Martell, J., & Heiman, J.R. (2006). Rape-myth congruent beliefs in women resulting from exposure to violent pornography: Effects of alcohol and sexual arousal. Journal of Interpersonal Violence, 21(9), 1208-1223.

Dines, G. (2010). Pornland: How porn has hijacked our sexuality. Boston: Beacon Press. Fisher, B. S., Cullen, F. T., & Turner, M. G. (2006). The sexual victimization of college women. Washington, DC: National Institute of Justice, US Department of Justice.

Fisher, W. A., & Barak, A. (2001). Internet pornography: A social psychological perspective on internet sexuality. Journal of Sex Research, 38(4), 312-323.

Foubert, J.D., Brosi, M.W., & Bannon, R. S. (2011). Pornography viewing among fraternity men: Effects on bystander intervention, rape myth acceptance and behavioral intent to commit sexual assault. Journal of Sex Addiction and Compulsivity, 18, 212-231.

Frable, D. E. S., Johnson, A. E., Kellman, H. (1997). Seeing masculine men, sexy women, and gender differences: Exposure to pornography and cognitive constructions of gender. Journal of Personality, 65(2), 311-355.

Hald, G.M., Malamuth, N.M., & Yuen, C. (2010). Pornography and attitudes supporting violence against women: Revisiting the relationship in nonexperimental studies. Aggressive Behavior, 36 (1), 14-20.

Kernsmith, P.D., & Kernsmith, R. M. (2009): Female pornography use and sexual coercion perpetration. Deviant Behavior, 30 (7), 589-610.

Kingston, D. A., Malamuth, N. M., Fedoroff, P., & Marshall, W.L. (2009). The importance of individual differences in pornography use: Theoretical perspectives and implications for treating sexual offenders. Journal of Sex Research, 46, 216-232.

Levin, M.E., Lillis, J. & Hayes, S.C. (2012). When is online pornography viewing problematic among college males? Examining the moderating role of experiential avoidance. Sexual Addiction and Compulsivity: The Journal of Treatment and Convention, 19 (3), 168-180.

Maddox, A. M., Rhoades, G. K., Markman, H.J. (2011). Viewing sexually-explicit materials alone or together: Associations with relationship quality. Archives of Sexual Behavior, 40, 441-448.

Malamuth, N. M., Addison, T., & Koss, M. (2000). Pornography and sexual aggression: Are there reliable effects and can we understand them? Annual Review of Sex Research, 11, 26–94.

Malamuth, N.M., Hald, G.M., & Koss, M. (2012). Pornography, individual differences in risk and men’s acceptance of violence against women in a representative sample. Sex Roles, 66, 427-439.

McMahon, S. & Banyard, V. (2012). How can I help? A conceptual framework for the prevention of sexual violence through bystander intervention. Trauma Violence & Abuse, 13, 3-14.

Norris, J., Davis, K.C., George, W.H., Martell, J., & Heiman, J.R. (2004). Victim’s response and alcohol-related factors as determinants of women’s responses to violent pornography. Psychology of Women Quarterly, 28, 59-69.

Owens, E. W., Behun, R. J., Manning, J. C, & Reid, R.C. (2012). The impact of internet pornography on adolescents: A review of the research. Sexual Addiction and Compulsivity, 19, 99-122.

Romito, P. & Beltramini, L. (2012). Watching pornography: Gender differences, violence and victimization. An exploratory study in Italy. Violence Against Women, 17(10), 1313-1326.

Sabina, C., Wolak, J.D., & Finkelhor, D. (2008). The nature and dynamics of internet pornography exposure for youth. Cyberpsychology & Behavior, 11 (6), 691-693.

Stack, S., Wasserman, I, & Kern, R. (2004). Adult social bonds and use of Internet pornography. Social Science Quarterly, 85, 75-88.

Vega, V. & Malamuth, N. M. (2007). Predicting sexual aggression: The role of pornography in the context of general and specific risk factors. Aggressive Behavior, 33, 104-117.

Yoder, V., Thomas, V., & Amin, K. (2005). Internet pornography and loneliness: An association? Sexual Addiction and Compulsivity, 12(1), 19-44.

While I  remember reading this in a publication I no longer have the reference. I was interested in it because over a 20year period of working with child sexual offenders and child internet pornography offenders (over a thousand) as a therapist there was a high frequency with which people stated that their introduction to child pornography was via the internet and adult pornography. Often the person at the time had no memory or realisation of the impact of their own childhood sexual abuse and made no connection with the images which attracted them and their own experience. They realised that they had "crossed a line" but felt unable to disclose or ask for help as they were ashamed. Most ( but not all) were aware that it was a crime and  they could be charged. No one knew where to go for help and all were afraid of the negative impact on their families and themselves if they disclosed. Some of them tried to use "will power" ineffectively and many vowed that if they were caught they would commit suicide. The local Police in Western Australia have been referring suicidal men who are facing charges to me and a group of my colleagues since 2010 and our names and some Community information can be accessed at wwww.preventingchildsexualabuse.org. I will search for the reference and get back to you if I find it. 

Considering that pornography has become the sex-ed vehicle of choice (whether willing or not) for this generation, the question is worth asking. The risk of desensitization with repeated exposure would seem to be a possibility, leading to searches for material that achieves the original effect. Perhaps it's no accident that law enforcement has reported the presence of younger perpetrators who also tend to focus on younger victims. As for the "show me the data" refrain that has so often permeated this type of discussion, I find myself reminded of the challenges on the medical side of the house that if the test doesn't match the clinical picture, you need a better test. It doesn't mean the clinical picture is wrong. Law enforcement that deals with sexually based offenders have long understood that there is a connection between particularly violent pornography and sexually based offenses. Teasing out what those connections are is worthwhile, especially given the growing prevalence of cyber-based crimes against kids.

I dont think that anyone can change sexual preferences of anyone by exposing him or her to pornography !

John D Foubert I have not yet read the full paper, but there is a good reference list and however, it may be of use - am aware my reply is about 6 years late!

Hannah L. Merdian1, Nick Wilson2, Jo Thakker1, Cate Curtis1, Doug P. Boer1 (2013)

"So why did you do it?": Explanations provided by Child Pornography Offenders

http://www.sexual-offender-treatment.org/117.html

Giovanni Portuesi

There are several reasons why someone would watch or exchange/trade in child pornography (or childhood sexual abuse as it is now termed) and not all are to do with paedophilia. e.g. for financial gain, or as a result of excessive porn use (and increased desensitization and compulsive/addictive viewing as mentioned by Karla Cunningham ) the person continues to search for the ultimate 'rush' and after trying out all categories of porn, ends up on a child porn website - this has included heterosexual adults without a prior sexual interest in children.

I think it's important to point out that the problem with pornography and interest toward child might be related to community stereotype instead of general population. In particular, Japanese animation often endorses the sexual joke that involves young children. Although mostly those were "jokes," the community of "anime" fans were exposed to perverted jokes bordering pornography both with adult characters and "loli" characters. I believe that long term exposure and "normalization" by the community might let people with interest to mature content to enjoy both adult porn and child semi-porn.

One such example is the recent uproar with anime "Mushoku tensei," which depicts a 30 year-old-man being reincarnated into a body of young children while retaining old memory and habit, using his child body to grope young girls breast. It was intended as a joke and not even important for the main plot. But it also portrays the idea that "such habit is normal" to the audience. Monogatari series in particular has plenty female children characters and multiple sexualized "jokes."

Treating everything as a "joke" is not a positive thing, especially when the border is vague and often nearly crossed.

https://digitalcommons.law.uga.edu/cgi/viewcontent.cgi?article=2257&context=gjicl

https://www.aljazeera.com/opinions/2014/8/11/manga-and-anime-japan-still-treating-children-as-sexual-objects/

Obviously it s impossibile to find such results. If you get excited by an adult woman, even if very young but after the puberal development , you have not a peversion. Everyone knows that observing a lot of pornograpy he actually does not like it s not able to change his sexual preferences.

Regarding Manga, maybe they could be a way to get excited for some people actually pedophile without be sanctioned, but you dont become pedophile regarding Manga.

Concerning the legal problem to have a sexual intercourse with a under eighteen girl ( if you like it), it s a legal problem. Indeed, Manga are ambigous in this field.

No, Sorry

Speakers at TED claims such things, but dont know of any research really

Perhaps the pornography sites themselves are not the issue overall however once you learn how to search for porn online you just have to add 'child' or 'bondage' etc which leads to other sites.

There is a similar trend pertaining to female abuse on pornography websites however as this is part and parcel of general male and female 'activities' I believe here that there is a correlation between this type of abusive porn and the expectations of men towards their female sexual partners.