The aim of this thesis was to investigate the hypothesis that women adjust their lumbar curvature to approach the suggested biomechanical optimum of 45.5 degrees in response to the presence of an attractive member of the opposite sex. The experiment was designed to examine the relationship between a) participants’ ratings of an attractive male confederate and the displayed change in deviation from the optimum displayed by women, and b) participants’ ratings of the attractive male confederate and the displayed change in the absolute degree of lumbar curvature, both while controlling for potential confounds such as participants’ self-perceived physical attractiveness, self-esteem, personality traits, and sociosexual orientation. Initial statistical analyses revealed a significant change in participants’ lumbar curvature pre- to post-exposure to the attractive male confederate. Subsequent analyses to examine the nature of the change indicated that socio-sexual orientation reliably predicted the change in lumbar curvature, but not the change in deviation from the optimum. The remaining variables predicted neither the change in lumbar curvature nor the change in deviation from the optimum significantly. This study is aimed at increasing our understanding of the behavioral display of lumbar curvature for self-promotion purposes in response to the presence of opposite sex.