The researchers had a theory. They thought that people who were bitten by infected mosquitoes, but recovered, were protected in the future.

VOA: special.2009.01.27

Others say the evidence is important, but that more evidence is needed to confirm the theory.

VOA: special.2009.01.20

But Professor Gaechter says his team's theory was that punishment has only low costs because it needs to be used rarely and works as a threat.

VOA: special.2009.03.03

But it is a scientific theory based on repeated observations, experiments,measurements and discoveries.

VOA: special.2009.12.01

But the broken windows theory was also disputed.

VOA: special.2009.03.03