People's eyes dilate when they are looking at people they find sexually appealing -- but new research from the University of Kent suggests that their response does not depend on whether the person being viewed is naked or clothed.
Researchers from the University's School of Psychology studied whether a stronger dilation for the preferred sex is produced when participants viewed images depicting higher levels of sexual explicitness compared to images low on sexual explicitness.Using eye-tracking technology in combination with highly controlled stimuli, the team found that pupillary responses to images of men and women appeared to be sex-specific but not sensitive to the sexual explicitness of the image.
Researcher Dr Janice Attard-Johnson said: 'We found that changes in pupil size when viewing images of men and women corresponded with participants' self-reported sexual orientation.
'This meant that in heterosexual men and women, dilation occurred during the viewing of opposite-sex people, but that these responses were comparable when participants viewed both naked and dressed targets.
'Our findings suggest that pupillary responses provide a sex-specific measure that is sensitive to both sexually explicit and non-sexually explicit content.'
Other research indicates that naked pictures of people elicit stronger signs of arousal than dressed images when this is measured using other physiological reactions, such as genital responses.
But researchers found this was not the case with pupillary responses, and suggest it is possible that a change in pupil size is elicited with lower levels of sexual arousal than is necessary for other physiological measures.
The research report, entitled Sex-specific but not sexually explicit: pupillary responses to dressed and naked adults, is published in the Royal Society Open Science journal. Its authors are Dr Attard-Johnson and Dr Markus Bindemann.
For further information contact Martin Herrema at the University of Kent Press Office.
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Note to editors
1. Participants in the study were 28 female and 24 male students with a mean age of 22.4 years. Only participants who reported to be exclusively or predominantly heterosexual were invited to take part.Participants were seated in a quiet windowless room with consistent artificial lighting. The participants' left eye was tracked and calibrated using a standard Eyelink process. Participants were invited to rate the sexual appeal of 72 images. Half of these images were based on photographs of six men and six women which were selected from XXX Porn-Star Portraits. Each of these targets was portrayed dressed, partially naked, and naked in matching poses on a plain background. Participants also viewed a set of control images whereby the content of these images was 'scrambled'.
2. Established in 1965, the University of Kent - the UK's European university - now has almost 20,000 students across campuses or study centres at Canterbury, Medway, Tonbridge, Brussels, Paris, Athens and Rome.It has been ranked: 23rd in the Guardian University Guide 2017; 23rd in the Times and Sunday Times University Guide 2017; and 25th in the Complete University Guide 2018.
In the Times Higher Education (THE) World University Rankings 2015-16, Kent is in the top 10% of the world's leading universities for international outlook and 66th in its table of the most international universities in the world. The THE also ranked the University as 20th in its 'Table of Tables' 2016.
Kent is ranked 17th in the UK for research intensity (REF 2014). It has world-leading research in all subjects and 97% of its research is deemed by the REF to be of international quality.
Along with the universities of East Anglia and Essex, Kent is a member of the Eastern Arc Research Consortium .
The University is worth £0.7 billion to the economy of the south east and supports more than 7,800 jobs in the region. Student off-campus spend contributes £293.3m and 2,532 full-time-equivalent jobs to those totals.
In 2014, Kent received its second Queen's Anniversary Prize for Higher and Further Education.