Why does running water make us want to use the toilet?

Why does running water make us want to go to the bathroom? What is IQ, and can you improve it? What is a Pica craving? Why isn't sperm damaged when it's frozen? Is there any evidence that links COVID vaccines to cancer rates? Is there a test to check whether honey is authentic or adulterated? What are hempcrete building materials? Why does it take so long to enrich uranium? What causes shingles? Dr Chris Smith and Clarence Ford have the answers... Like this podcast? Please help us by supporting the Naked Scientists (https://www.thenakedscientists.com/donate)