Rumours multiply in the atmosphere of fear. For instance, if you are getting scared of the danger of earthquake, you will easily believe on the rumours of earthquake spread around you.

Doubt also one of the factors that force you to believe on rumours. For example, you are in abroad and you doubt your wife. In this situation, if you heard something negative about your wife, you might not think that the rumour can be untrue.

Ignorance is another cause you easily believe on rumours. For example, if somebody says you that a scientific research happening somewhere can ruin the life on the earth, then you may accept the rumour because you may not have idea and knowledge about that research.

Some rumours are promoted by coincidence. For example, you heard quarrel in your neighbourhood. You heard the sound of ambulance in the midnight. In this situation, if you don’t see your neighbour in the morning, you may think that they have been hospitalized. 
Discovered by Don Prince