The reasons why boxers are said to be superior seem obvious. If the purpose of the scrotum is to keep the testicles away from the heat at the core of the body, briefs would seem to defeat that purpose.
"It is consistent with the concept that excess heat can be detrimental to testicular function," said Williams.
But the evidence doesn't seem to back that idea.
"There are no well-controlled studies that look into the choice of underwear, briefs versus boxers," said Williams. "There's no scientific data I know of ... head-to-head studies of boxers versus briefs showing a difference."
A study from the State University of New York at Stony Brook was published in the Journal of Urology in 1998 where 97 men with infertility were examined to see if their underwear choice made a difference.
Researchers found an average difference of less than half of a degree Fahrenheit in temperature of the scrotum between men who wore one underwear type or the other, with a margin of error larger than the difference.
"It is unlikely that underwear type has a significant effect on male fertility," wrote the authors. "Routinely advising infertility patients to wear boxer shorts cannot be supported by available scientific evidence."
If you are trying to avoid excess heat in the region, putting a computer that generates heat in your lap may not be the best idea.
"If there is excessive heat put out by the laptop, excess heat exposure from the laptop to the testicles may have a detrimental effect," said Williams.
"If there is prolonged use on the lap ... it's important to be aware of that," he said.
A 2005 study from Stony Brook also indicated that using a laptop on the lap can elevate the temperature of the scrotum several degrees.
But other concerns about modern electronics aren't as well backed up.
When it comes to radio waves generated by cell phones or wi-fi from laptops, it's unclear what if anything they do to sperm.
"This effect remains to be determined, but researchers are looking into that," said Williams. "Whether it's clinically significant remains to be determined."
"The take-home message on that is to avoid excess heat," said Williams. "Any prolonged exposure to excess heat can be detrimental to the production of sperm and sperm quality."
He noted that other heat sources, such as saunas, could present a similar problem.
"If men are regularly hot-tubbing or using the sauna and if they have impaired sperm quality or sperm counts, that would be one strategy to try to improve the sperm count or sperm quality."
While hot tubs can present a problem, Williams noted that studies have not shown how much exposure to them is too much.
Morgentaler noted that the problems hot tubs and saunas present are not surprising.
"The testicles live outside the body for good reason," he said. "Heat is bad for sperm production, so bad that…humans and many but not all mammals have the testicles outside the body in a pouch called the scrotum to keep the testicles cooler."
While noting that a fever can have a similar effect, Morgentaler said that a man who likes the occasional hot dip shouldn't be too alarmed that he is ruining his chances for fatherhood.
"An occasional hot bath or a single episode of a Jacuzzi is probably not enough to do anything," he said.
Avoid, If Only For Other Reasons