The Annals of Improbable Research on Thursday awarded the Ig Nobel Prizes to 10 "improbable" research projects, including studies into how dirty money really is, whether clickers can help train budding surgeons and more.

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The 29th annual Ig Nobels recognize researchers who have done research that "make[s] people laugh, and then think," according to the Annals. The prizes aim to "celebrate the unusual, honor the imaginative—and spur people's interest in science, medicine, and technology."

The winners

The prizes cover a wide range of topics, from physicians to peace. Here are the 10 Ig Nobel Prize winners:

Physics prize: The prizewinning team of researchers from Georgia Tech set out to determine "how and why wombats make cube-shaped poo." The researchers analyzed a few wombat carcasses and found that the shape of wombats' poop is due to the shape and flexibility of their intestines as well as the fact that they live in dry environments.

Anatomy prize: Roger Mieusset, a fertility specialist at the University of Toulouse in France, and Bourras Bengoudifa set out to determine if there is any validity to the claim that men's left scrotums are usually hotter in temperature than the right. After measuring testicle temperature in young French postmen, the researchers found that there is, in fact, a difference in temperature between the two sides, which could "contribute to the asymmetry in the male external genital organs," they said.

Medicine prize: Silvano Gallus of the Mario Negri Institute for Pharmacological Research in Milan won the prize for conducting several studies that investigated whether pizza could "protect against illness and death," according to the Annals. Between 2003 and 2006, Gallus and his colleagues conducted studies on whether pizza could reduce the risk of acute myocardial infarction, as well as breast, ovarian, and prostate cancer. The studies never came to a firm conclusion, but Gallus did find that pizza offered some protection against illness and death, "if the pizza is made and eaten in Italy," according to Gallus.

Medical Education: Karen Pryor a U.S. behavioral psychologist, and Theresa Mckeon of TAGteach International won the prize for their 2016 study that found that an animal training technique, known as click training, could be used to train surgeons to perform orthopedic surgery. For the study, the researchers tested whether the auditory conditioning tool could be used to teach surgeons how to perform two surgical tasks. The results revealed the medical students who underwent click training took longer to learn the procedures, but performed the tasks more precisely.

Biology prize: Studies have shown that cockroaches can become magnetized, but Ling-Jun Kong of Nanyang Technological University in Singapore and his colleagues wanted to find out if dead cockroaches magnetized differently than living cockroaches. Using a technique called magnetorelaxometry (MRX), the researchers measured how dead and living American cockroaches become magnetized and found that live cockroaches' magnetic field decays faster than dead cockroaches.

Chemistry prize: Researchers from Japan won the prize for determining how much saliva a typical five-year-old produces each day. The researchers in the 1995 study examined how different foods, including steamed rice, mashed potatoes, and apples, affected the amount of saliva children produced by having the participants chew the foods and spit them out. The researchers then subtracted how much the food weighed original from how much it weighed after it was chewed. 

Engineering prize: Iman Farahbakhsh, an engineer from Iran, invented a dishwasher-like diaper-changing machine. Farahbakhsh received a patent for the machine in 2018. "Once the infant is placed inside the apparatus, various steps may in some cases be carried out automatically without needing the operator to touch the infant or interact manually with the diaper or infant during the changing process," the patent states.

Economics prize: People assume that money collects bacteria from being passed from hand to hand, but a group of researchers set out to determine which world currency was the most contaminated. The researchers tested the the Euro, U.S. Dollar, Canadian Dollar, Croatian Luna, Romanian Leu, Moroccan Dirham, and Indian Rupee for strains of Staphylococcus aureus and Escherichia coli, and found that the polymer-based Romanian Leu was the only currency that transferred both bacterial strains.

Peace prize: The winning group of scientists in a 2012 study measured the pleasurability of scratching an itch. After using a legume to induce itching all over the body, the researchers found that, because the itching was more intense on participants' backs and ankles, the degree of pleasurability from scratching was higher.

Psychology prize: Fritz Strack, a German social psychologist, won this prize for disproving his own findings. In 1998, Strack and his colleagues published findings that holding a pen in your mouth causes people to smile, which can make a person happier. But when he revisited the findings in a 2016 study, Strack failed to replicate his previous conclusion and didn't find evidence that smiling impacted a person's degree of happiness.

The awards were presented at Harvard University, with former Nobel Prize winners in attendance (Oullette, Ars Technica, 9/12; "About the Ig Noble Prizes," Improbable.com; Sample, The Guardian, 9/12).