---
title: "List of common misconceptions about science, technology, and mathematics"
chunk: 12/16
source: "https://en.wikipedia.org/wiki/List_of_common_misconceptions_about_science,_technology,_and_mathematics"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T03:28:18.528573+00:00"
instance: "kb-cron"
---

=== Sexuality and reproduction ===
Older adults are not necessarily sexually inactive nor have they lost interest in sex; although the frequency of sexual activity tends to decline with age. One survey in England of people aged 60–69 recorded 86% of men and 60% of women as sexually active.
It is not possible to get pregnant from semen released in a commercial swimming pool without penetration. The sperm cells would be quickly killed by the chlorinated water and would not survive long enough to reach the vagina.
An examination of the hymen is not an accurate or reliable indicator that a woman or girl has had penetrative sex, because the tearing of the hymen may have been the result of some other event, and some women are born without one. Virginity tests, such as the "two-finger" test, are unscientific.
Hand size and foot size do not correlate with human penis size, but finger length ratio may.
While pregnancies from sex between first cousins do carry a slightly elevated risk of birth defects, this risk is often exaggerated. The risk is 5–6% (similar to that of a woman in her early 40s giving birth), compared with a baseline risk of 3–4%. The effects of inbreeding depression, while still relatively small compared to other factors (and thus difficult to control for in a scientific experiment), become more noticeable if isolated and maintained for several generations.
Having sex before a sporting event or contest is not physiologically detrimental to performance. In fact some studies suggest that sex prior to sports activity can elevate male testosterone levels (which could potentially enhance performance for male athletes), while long periods of abstinence can reduce those levels.
The heightened sensitivity some women experience at the G-spot is not due to it being a distinct anatomical structure, but rather because pressure in that area may stimulate other internal structures, notably the Skene's gland. Many sexologists take issue with the term, concerned that women who "fail to find their G-spot" may feel abnormal.
Closeted or latent homosexuality is not correlated with internalized homophobia. A 1996 study claiming a connection in men has not been verified by subsequent studies, including a 2013 study that found no correlation.
The menstrual cycles of women who live together do not tend to synchronize. A 1971 study made this claim, but subsequent research has not supported it.
Having an abortion does not increase someone's risk of developing breast cancer. Some smaller, less reliable early studies suggested that abortion could be linked to breast cancer, but the scientific community has concluded that abortion does not cause breast cancer.
There is no evidence that English-speaking Christian missionaries encouraged converts to use the missionary position in the colonial era. This notion probably originated from Alfred Kinsey's Sexual Behavior in the Human Male (1948) through misunderstandings and misinterpretations of historical documents.

=== Skin and hair ===
Water-induced wrinkles are not caused by the skin absorbing water and swelling. They are caused by the autonomic nervous system, which triggers localized vasoconstriction in response to wet skin, yielding a wrinkled appearance.
A person's hair and fingernails do not continue to grow after death. Rather, the skin dries and shrinks away from the bases of hairs and nails, giving the appearance of growth.
Shaving does not cause terminal hair to grow back thicker or darker. This belief is thought to be due to the fact that hair that has never been cut has a tapered end, so after cutting, the base of the hair is blunt and appears thicker and feels coarser. The fact that short hairs are less flexible than longer hairs contributes to this effect.
MC1R, the gene mostly responsible for red hair, is not becoming extinct, nor will the gene for blond hair do so, although both are recessive alleles. Redheads and blonds may become rarer but will not die out unless everyone who carries those alleles dies without passing their hair color genes on to their children.
Acne is not caused by a lack of hygiene or eating fatty foods, though certain medications or a carbohydrate-rich diet may worsen it.
Dandruff is not caused by poor hygiene, though infrequent hair-washing can make it more obvious. The exact causes of dandruff are uncertain, but they are believed to be mostly genetic and environmental factors.