2nd October 2003
The results of a new study by a team of British psychologists released today provide powerful new evidence that sexual orientation is 'hard-wired' in the human brain before birth.
Dr Qazi Rahman of the University of East London (UEL) has been working with Dr Veena Kumari and Dr Glenn Wilson of the Institute of Psychiatry to investigate sex differences in the startle response - our eye-blink reaction to sudden loud noises.
The team discovered significant differences in the response between male and female, and heterosexual and homosexual subjects. Because the startle response is known to be involuntary rather than learned, this strongly indicates that sexual orientation is largely determined before birth.
An estimated 4% of men and 3% of women are homosexual, but the hypothesis of a 'gay gene' remains controversial. Recent studies report links between foetal development, testosterone levels and adult sexuality, but this study offers the first independent evidence of a non-learned neurological basis for sexual orientation.
Dr Rahman said, "The startle response is pre-conscious and cannot be learned. It is mediated by an ancient region of the brain called the limbic system which also controls sexual behaviour. This is very strong evidence that female sexual orientation at least may be 'hard-wired' in this region."
The researchers used a technique known as prepulse inhibition (PPI) to test male and female, gay and straight volunteers. The subjects were unexpectedly startled by loud noises preceded by a quieter noise. Dr Rahman measured the strength of the involuntary eye-blink responses and compared them with those to a loud noise alone - the lower the response, the stronger the level of inhibition.
The results showed clear differences between the groups. At the extreme ends of the scale, heterosexual men showed a PPI of 40%, compared with 13% for heterosexual women. Lesbians, with a PPI of 33%, showed a markedly stronger inhibition than straight women, while gay men averaged 32%, an intermediate response slightly lower than for straight men.
Dr Glenn Wilson, a leading figure in psychology research in the UK said: "The PPI test is a powerful measure of the brain's ability to filter and process information. Information processing is fundamental to the way the brain works, and these results suggest evolutionary divergence between male and female oriented brains."
Dr Rahman has spent six years investigating the neurological basis of human sex differences and sexual orientation and is now looking to explore the relevance of these findings to gender differences in certain psychiatric illness and gay and lesbian mental health.
Dr Rahman said: "These findings may well affect the way we as a society deal with sexuality and the issues surrounding sexual orientation. They may also have far-reaching health implications, offering clues as to why men and women, and gay men and lesbians, sometimes suffer from different types of mental health disorders. If we know that certain groups differ from each other in brain function or a biological marker then we are in a position to provide better treatments which are tailored to suit particular groups".
The paper entitled Sexual Orientation Related Differences in Prepulse Inhibition of the Human Startle Response appears in the October issue of the international journal Behavioral Neuroscience, published by the American Psychological Association.
Ends/.
Contact: Patrick Wilson on 020 8223 2061 or mobile 07951 797 975
Dr Qazi Rahman is available for interview by arrangement; proof copies of the paper Sexual Orientation Related Differences in Prepulse Inhibition of the Human Startle Response are available on request.
Dr Qazi Rahman is a Lecturer at the School of Psychology, University of East London, and was formerly Lecturer in Neuropsychology at the Institute of Psychiatry and GKT School of Medicine, King's College, London. His research expertise includes the biological basis of human sex differences and sexual preference, and is the leading UK young scientist in this area.
Dr Glenn Wilson is Reader in Personality at the Institute of Psychiatry and Adjunct Professor of Psychology within the University of Nevada, Reno (USA). He has published over 100 scientific articles and 30 books and is ranked within the 10 most frequently cited British psychologists.
Dr Veena Kumari is Wellcome Senior Research Fellow in Basic Biomedical Science and Senior Lecturer in Psychology at the Institute of Psychiatry. Her research expertise is in psychophysiology, human startle response, brain imaging and schizophrenia.
The Institute of Psychiatry is part of King's College London and closely affiliated to the South London and Maudsley NHS Trust. The Institute is a world-renowned centre for treatment, research and training in psychiatry and mental health. The organisation is involved in pioneering new and improved ways of understanding and treating mental illness and brain disease. Its wide-ranging field of work includes depression, eating disorders, brain imaging, genetics and psychosis. The Institute was one of only two organisations in the field of psychiatry which received a five star rating in the 2001 Research Assessment Exercise (RAE) conducted by the UK's higher education funding councils.
UEL's School of Psychology is one of the largest departments of its kind in the UK and is recognized nationally and internationally for excellence in teaching and research. It has research expertise in every area of Psychology including child development, health and social psychology, cognitive neuropsychology, recreational drug use research and Virtual Reality applications. UEL is London's leading centre for psychology training and offers the largest array of professional doctorates in Clinical Psychology, Educational Psychology, Occupational Psychology and Counselling.
University of East London: Our vision is to achieve recognition, both nationally and internationally, as a successful and inclusive regional university proud of our diversity, committed to new modes of learning which focus on students and enhance their employability, and renowned for our contribution to social, cultural and economic development, especially through our research and scholarship.
© 2003
For a general description of these pages and an explanation of how they should work with screenreading equipment please follow this link:Link to general description
For further information on this web site's accessibility features please follow this link:Link to accessibility information
The following message does not apply to screenreader users:
You will still be able to access all the essential content of this web site, but it will not look, or function, exactly as intended.
