[1991] Mutilated Humanity by Ashley Montagu

Quotes
A neurologist who saw the results to postulated that the data indicated that circumcision affected most intensely the portions of the victim's brain associated with reasoning, perception and emotions. Follow up tests on the infant one day, one week and one month after the surgery indicated that the child's brain never returned to its baseline configuration. In other words, the evidence generated by this research indicated that the brain of the circumcised infant was permanently changed by the surgery. 
    Our problems began when we attempted to publish our findings in the open medical literature. All of the participants in the research including myself were called before the hospital discipline committee and were severely reprimanded. We were told that while male circumcision was legal under all circumstances in Canada, any attempt to study the adverse effects of circumcision was strictly prohibited by the ethical regulations. Not only could we not publish the results of our research, but we also had to destroy all of our results. If we refused to comply, we were all threatened with immediate dismissal and legal action. [2009 oct] MRI Studies: The Brain Permanently Altered From Infant Circumcision by Dr. Paul D. Tinari Ph.D.

The early imprinting of excruciating pain on the pleasure networks of the brain likely encodes for sado-masochistic behavior in the adult. Male Circumcision in the USA: A Human Rights Primer by Rich Winkel