Females make a much greater investment in reproduction: nine months of pregnancy, the health risks of giving birth, and years of caring for the child. Males, on the other hand, have a much lower level of investment in reproduction and can be as low as zero investment.

Evolutionary theory states that due to the greater obligatory investment in reproduction, females should be much choosier in selecting a mate than males, while males are motivated to engage in as many reproductive opportunities as possible. According to evolutionary psychologist Martie Hazelton,

Within a given population, males who miss reproductive opportunities with some regularity will be out-reproduced by males who do not. [Because] males face greater costs of missing sexual opportunities than of pursuing disinterested females, they should be selected to err on the side of pursuit, even if this causes them to make more errors overall.

Source.

This evolutionary pressure causes males to have a bias known as “overperception bias” where men overperceive women’s sexual interest in them. This is manifested where men interpret mere friendliness by a female as sexual interest. An example highlighted in the Hazelton paper captures the bias perfectly:

Recently 13 employees of the Safeway supermarket chain, 12 of them women, filed grievances over the supermarket’s ‘‘service-with-smile’’ policy. The employees reported that customers, nearly all of whom were men, misconstrued their obligatory friendliness as sexual interest. One employee reported that the unwanted
sexual attention and harassment was so extreme that she was forced to hide in the back room to avoid customers who repeatedly ‘‘hit on’’ her and followed her to her car.

Overperception bias can be heightened by power differences. A study by researchers at Florida State University found that “power, coupled with the presence of an opposite-sex social target, was enough to elicit biased perceptions of sexual interest [and thus] power can set the stage for harassment, because it leads to a fundamental misperception of the social environment.” Source.

A key point is that our reproductive drive is a foundational motivating force in humans, yet the two genders approach reproduction from very different perspectives due to evolution. While this obvious, knowledge of the specific point that males are more likely than females to misperceive sexual interest from a member of the opposite sex can lead to change in behavior. If overperception bias were taught in schools and was a component of sexual harassment training, this knowledge might mitigate painful experiences for both males and females.