In dorsal digit ratios, in contrast, strong sexual dimorphism occurs in those of digit 5, with women having shorter fifth digits on average. In palmar digit ratios, strong sexual dimorphism occurs in those of digit 2. In keeping with these hormonal differences, the digit ratios are sexually dimorphic, being lower in men than in women. Furthermore, one frequently cited paper on the topic has failed to be replicated. Larger studies have also failed to find evidence for 2D:4D being a marker for prenatal androgen exposure. However, subsequent studies have found no relationship between 2D:4D ratios and testosterone or estradiol levels, or even the testosterone to estradiol ratio. There are also studies that suggest that the palmar 2D:4D ratio is influenced by prenatal estrogen exposure, and that it thus correlates negatively not with prenatal testosterone alone, but rather with the prenatal testosterone-to-estrogen ratio (T:O). The ratio of two digits in particular – the palmar 2nd ( index finger) and 4th ( ring finger) – is supposedly affected by fetal exposure to hormones, in particular to testosterone, and other androgens this 2D:4D ratio could therefore be considered a crude measure for prenatal androgen exposure, with lower 2D:4D ratios pointing to higher prenatal androgen exposure. It has been suggested that because academics have accepted a variety of techniques and equipment (such as calipers, radiography and photocopy), researchers deliberately record multiple measurements and report only those which have significant findings, a form of reporting bias. Other digit ratios are also similarly calculated in the same hand. Moreover, differential placing of flexion creases is a factor in the palmar digit ratio. A study has shown that, compared to the palmar digit ratio, the dorsal digit ratio is a better indicator of bone digit ratio. Measurement of the digits on the dorsal ('back-side') hand, from the tip of the finger to the proximal phalange-bone protrusion (which occurs when digits are bent at 90 degrees to the palm), has recently also gained acceptance. The digit length is typically measured on the palmar (ventral, 'front', 'palm-side') hand, from the midpoint of the bottom crease to the tip of the finger. Although studies have claimed to show a correlation between the 2D:4D digit ratio and various physical and behavioral traits, these studies have drawn criticism for irreproducible or contradictory findings, exaggerated claims of usefulness, and lack of high quality research protocols. The 2D:4D ratio is the most studied digit ratio and is calculated by dividing the length of the index finger of a given hand by the length of the ring finger of the same hand. The digit ratio is the ratio of the lengths of different digits or fingers on a hand. The hand is placed on the edge of a table so that fingers are rested on table while making an angle of 90 degrees to the palm. Image shows the measurement procedure of dorsal digit length using vernier calipers.

2d 4d ratio study pdf