Yet, as noted above and as is normal for most genetic research, especially as it relates to complex human behaviors for example love and romance, the data supporting genetic attraction is extremely inconsistent. A high number of studies, calling for distinct experimental methods and residents, have now been reported, and they give discordant results. While some research has supported the theory that MHC gene diversity drives human attraction, other studies have reported different or conflicting results. A number of research have found that people prefer sexual partners with only fairly different or even similar MHC forms, others have found that MHC diversity is discovered by facial contour instead of odor, and still more have discovered that women in committed relationships are most attracted to guys with different MHC alleles. A number of studies have also discovered that women on birth control pills have a tendency to favor guys with the exact same MHC forms, the reverse of their peers not on the pill. As one scientific overview of the whole body of data reasoned, the assorted evidence ... makes it difficult to draw certain conclusions, but the high number of studies showing some MHC involvement indicates there is really a happening that needs additional work to elucidate."