Lordosis in Humans.

Despite progress in attractiveness research, we have yet to identify many fitness-relevant cues in the human phenotype or humans' psychology for responding to them. Here, we test hypotheses about psychological systems that may have evolved to process distinct cues in the female lumbar region. The Fetal Load Hypothesis proposes a male preference for a morphological cue: lumbar curvature. The Lordosis Detection Hypothesis posits context-dependent male attraction to a movement: lordosis behavior. In two studies (Study 1 N: 102, Study 2 N: 231), we presented men with animated female characters that varied in their lumbar curvature and back arching (i.e., lordosis behavior). Irrespective of mating context, men's attraction increased as lumbar curvature approached the hypothesized optimum. By contrast, men experienced greater attraction to lordosis behavior in short-term than long-term mating contexts. These findings support both the Lordosis Detection and Fetal Load Hypotheses. Discussion focuses on the meaning of human lordosis and the importance of dynamic stimuli in attractiveness research.

The Development and Psychometric Evaluation of a New Mating Effort Questionnaire.

In this study, we review the psychometric literature on mating effort and find that extant instruments (1) have not been adequately evaluated in terms of internal structure and measurement invariance, and (2) disproportionately focus on mate retention and intrasexual competition tactics designed to repel competitors, relative to attraction and investment effort. To address these gaps in the literature, we carried out two studies to develop and validate a new Mating Effort Questionnaire (MEQ). In Study 1, we report a pilot study in which participants' responses to an item pool were submitted to exploratory factor analysis. In Study 2, we replicated the structure found in Study 1 using confirmatory factor analysis in an independent sample. A three-factor solution yielded the best fit. The three factors reflected respondents' allocation of energy to attracting high mate value partners when already mated, seeking out romantic partners when single, and investing in their current romantic partner and relationships. Strong partial measurement invariance held across the sexes, implying that observed scores may be used to compare them. We also found evidence of concurrent validity via associations between the MEQ and constructs such as sociosexual orientation, K-factor, mate retention behaviors, and respondents' sexual behavior. These findings suggest that the MEQ is a valid and novel measure of individual differences in mating effort which is well suited to complement existing mating effort measures.

Why Women Wear High Heels: Evolution, Lumbar Curvature, and Attractiveness.

Despite the widespread use of high-heeled footwear in both developing and modernized societies, we lack an understanding of this behavioral phenomenon at both proximate and distal levels of explanation. The current manuscript advances and tests a novel, evolutionarily anchored hypothesis for why women wear high heels, and provides convergent support for this hypothesis across multiple methods. Using a recently discovered evolved mate preference, we hypothesized that high heels influence women's attractiveness via effects on their lumbar curvature. Independent studies that employed distinct methods, eliminated multiple confounds, and ruled out alternative explanations showed that when women wear high heels, their lumbar curvature increased and they were perceived as more attractive. Closer analysis revealed an even more precise pattern aligning with human evolved psychology: high-heeled footwear increased women's attractiveness only when wearing heels altered their lumbar curvature to be closer to an evolutionarily optimal angle. These findings illustrate how human evolved psychology can contribute to and intersect with aspects of cultural evolution, highlighting that the two are not independent or autonomous processes but rather are deeply intertwined.