The annual Ig Nobel awards were presented last night, with the US taking three of the 10 prizes for the most bizarre or unusual scientific research.

The Medicine prize went to Dan Ariely of Duke University for demonstrating that high-priced fake medicine is more effective than low-priced fake medicine.

Meanwhile, three researchers at the University of New Mexico won the Economics prize for their paper entitled Ovulatory Cycle Effects on Tip Earnings by Lap Dancers: Economic Evidence for Human Estrus? which linked lap dancers' earnings to their menstrual cycles.

The Physics prize was scooped by Dorian Raymer of the Ocean Observatories Initiative at Scripps Institution of Oceanography and Douglas Smith of the University of California, San Diego for their work establishing the mathematical reason for string tying itself in knots over time.

American scientists from the University of Puerto Rico, The Fertility Centers of New England, Boston University School of Medicine and Harvard Medical School shared the Chemistry prize after proving that Coca-Cola is an effective spermicide.

However, the judges split their award with the Taipei Medical University which proved that it is not effective.

Other winners included research into how to make potato crisps sound fresher when eaten, a paper on training amoeba to solve puzzles, and the Literature prize for the paper You Bastard: A Narrative Exploration of the Experience of Indignation within Organizations.

The prizes were awarded at a riotous dinner at Harvard University last night.