Abstract
Objective measures of sexual interest are important for research on human sexuality. There has been a resurgence in research examining pupil dilation as a potential index of sexual orientation. We carried out a meta-analytic review of studies published between 1965 and 2020 (Mdn year = 2016) measuring pupil responses to visual stimuli of adult men and women to assess sexual interest. Separate meta-analyses were performed for six sexual orientation categories. In the final analysis, 15 studies were included for heterosexual men (N = 550), 5 studies for gay men (N = 65), 4 studies for bisexual men (N = 124), 13 studies for heterosexual women (N = 403), and 3 studies for lesbian women (N = 132). Only heterosexual and gay men demonstrated discrimination in pupillary responses that was clearly in line with their sexual orientation, with greater pupil dilation to female and male stimuli, respectively. Bisexual men showed greater pupil dilation to male stimuli. Although heterosexual women exhibited larger pupils to male stimuli compared to female stimuli, the magnitude of the effect was small and non-significant. Finally, lesbian women displayed greater pupil dilation to male stimuli. Three methodological moderators were identified—the sexual explicitness of stimulus materials, the measurement technique of pupillary response, and inclusion of self-report measures of sexual interest. These meta-analyses are based on a limited number of studies and are therefore preliminary. However, the results suggest that pupillary measurement of sexual interest is promising for men and that standardization is essential to gain a better understanding of the validity of this measurement technique for sexual interest.
Highlights
The fact that the pupil of the human eye responds to changes in brightness levels within our visual environment is well known to most people
The overall effect sizes for these observer groups ranged from small to moderate across studies, to other measures of sexual interest using cognitive tasks (e.g., Viewing Time, Ó Ciardha et al, 2018), but smaller effect sizes relative to those obtained with genital arousal measurements (e.g., Jabbour et al, 2020; Semon et al, 2017)
While pupillary responses were first explored as a measure of observers’ sexual interest in others in the 1960s, there has been an increase in research in this field with modern eyetracking equipment in recent years
Summary
Studies available in peer-reviewed journals, books or book chapters, as well as unpublished dissertations, abstracts, conference papers, and preprints, were included in this review up until January 2020. To be included studies needed to meet the following criteria: They measured and compared pupil responses to visual stimuli of adult men and women to measure sexual interest; included at least one sample of male or female observers identifying as heterosexual, gay, or bisexual; stimuli (video or images) used depicted either a man or a woman but not both; a sample size of at least 5 observers per group; and contained sufficient information to calculate effect size d. From the 17 studies, 16 included comparisons for heterosexual men, 7 for gay men, 4 for bisexual men, 14 for heterosexual women, 3 for lesbian women, and 2 for bisexual women Before commencing analysis, another search was performed in January 2020 that revealed two additional studies for heterosexual men and women.
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