The scientific study of human sexuality has undergone a profound transformation since the mid-twentieth century, yet methodological progress has slowed toward a structural plateau. This article argues that the plateau has two interlocking causes: the effective removal of direct participant observation (DPO) from the research toolkit under institutional ethical mandates, and an unexamined gender-epistemic bias embedded in the foundational frameworks the field has never rigorously retested. Both Kinsey’s descriptive architecture and Masters and Johnson’s Model of Sexual Response Cycle (MSRC) were constructed primarily from a male-positioned vantage point. The MSRC in particular has never constituted a valid model of female sexual response; its apparent applicability to women reflects decades of education and cultural conditioning rather than empirical validation under naturalistic conditions. Three converging lines of evidence support this argument: phenomenological indicators of a qualitatively distinct female sexual response architecture; cross-population data suggesting that female conformity to the MSRC increases with education exposure rather than biological invariance; and cross-cultural folk observation traditions that independently documented the male-female developmental divergence that academic sexology has not formally modeled. The article further shows that even the most technically sophisticated indirect instruments — neuroimaging, genital photoplethysmography, vaginal blood flow measurement — share an epistemological ceiling with self-report methods, incapable of generating the naturalistic behavioral data that DPO uniquely provides. The article concludes that the field requires a foundational rerun of DPO — at comparable scale and duration to Masters and Johnson’s original work — designed specifically to investigate female sexual response free of male-oriented parameters and terminology. A new observational platform, governed by agentic AI and embodied in a compact AI field observer, is proposed as the structural pathway that makes such a rerun ethically feasible for the first time. Keywords: sexuality research; research plateau; direct participant observation; female sexual response; MSRC critique; gender-epistemic bias; Masters and Johnson; agentic AI; AI-embodied observation; sexual dysfunction
Jiang Zhao (Wed,) studied this question.