Sexology is a broad, interdisciplinary, field with a long tradition of empirical research. Comprehensive quantitative and qualitative studies have been conducted since the 20th century, providing abounding evidence. As the area is informed by diverse theoretical backgrounds, a wide range of methods have been applied to sex research over time.While the World Health Organization 1 claims that sexual health refers to a state of physical, emotional, mental, and social well-being in relation to sexuality, beyond the absence of disease, dysfunction or infirmity, most studies from the past decades have focused on sexual function and behavior. Broader aspects such as quality of sex life, sexual violence, sexual beliefs, and sexual satisfaction have received less attention. The narrowing of sexuality around sexual function might be misleading in the understanding of the sexual complaints that make a person seek for sexual healthcare. The inclusion of broader aspects might foster a more comprehensive perspective and produce more effective, culturally competent, treatment options.From Masters' and Johnson's observations in the 1960s until today, most of the knowledge available on sexual function and the psychophysiological processes involved in sexual response was derived from experiments that may seem exotic to a naïve observer. Unconventional instruments are used to measure participants' genital responses, like vaginal and penile plethysmographs or genital thermographs, and experimental tasks may include masturbating in the lab or watching a pornographic video, while monitored by eye-trackers, electroencephalography, or functional magnetic resonance imaging. Clinical trials on sexual medicine interventions have also risen in the last 30 years, driven mostly by efforts to develop medications for sexual disfunctions.Ethical guidelines limit the number of sexual behaviors that can be observed or experimentally manipulated in laboratory settings. Generalizability of these findings may additionally be biased by the artificial context and observer effects. Thus, for the study of sexual behavior, indirect observation is broadly used, with methods that include interviews, self-report questionnaires or retrieval of clinical records and public databases.Cross-sectional surveys are the most used alternative for obtaining information about sexual behavior and other dimensions of human sexuality. Robust estimates of the prevalence of sexual behaviors and their determinants in the population have been provided by surveys in the past years. Research strategies to minimize measurement error have been applied, from sample selection to questionnaire content, design, and data collection 2 .Random probability sampling methods are used to reduce volunteer bias. Volunteers in sex research tend to be more sexually experienced, sensation seeking, to have more relaxed sexual attitudes and behaviors than the general population. Achieving good response rates is thus essential to improve the representativeness of the survey and reduce participation ...
