Open up your hand and look at the relative lengths of your fingers. If you are a woman, it is likely the case that your index finger (i.e., the one closest to your thumb) is roughly the same length as your ring finger (i.e., the one closest to your pinky). Men on the other hand have slightly longer ring fingers as compared to their index fingers. This is referred to as the second (index) to fourth (ring) digit ratio (2D:4D for short). In the parlance of evolutionary theory, the 2D:4D ratio is a sexually dimorphic morphological trait, which is in part shaped by in utero exposure to sex-specific androgens.
Over the past ten years or so, there has been an explosion of scientific research on the effects of the 2D:4D ratio on innumerable phenomena including: financial trading, gender identity, sexual orientation, personality traits (e.g., aggression, cooperation, dominance, jealousy, Big-Five), reproductive success, athletic ability (e.g., skiing, fencing), musical ability, dancing ability, spatial ability, academic success, menarche, propensity for specific diseases, facial symmetry, career interests, semen quality, and offspring sex ratio.
Some have argued that the 2D:4D is nothing more than a "sophisticated" form of palmistry. Others have ventured that it belongs with astrology and phrenology, former scientific fields that are now completely discredited. The reality is that the sheer number of papers that have yielded robust 2D:4D effects in prestigious peer-reviewed scientific journals suggests that it is going to take more than a flippant dismissal, as the means of critiquing this thriving research stream.
Recently, I was appointed to a university-wide chaired position. One of the mandates of my chair is to conduct new empirical studies within my work at the nexus of evolutionary theory and consumption. In one of the projects, I am exploring the relationship between the 2D:4D ratio and a wide range of consumption phenomena possessing strong sex-specificity. For example, I am planning on investigating the relationship between the 2D:4D ratio and participation in extreme sports (possibly with some graduate students at SUNY-Binghamton). Along with some of my current graduate students (Eric Stenstrom, Zack Mendenhall, and Marcelo Nepomuceno), we are investigating the relationship between 2D:4D and conspicuous consumption, as well as that between the 2D:4D and specific product preferences (e.g., male versus female dominated video games). This past fall, my students collected the first round of data, the results of which were somewhat promising. The next round of data collection should be underway shortly. Stay tuned for some hopefully exciting results.