I have frequently found the following statement being used to justify the use of a variety of media and methods in all sorts of training and communication programmes:
"We retain 10% of what we read. We retain 20% of what we hear. We retain 30% of what we see. We retain 50% of what we hear and see. We retain 70% of what we say. We retain 90% of what we do."
Frankly, I don't believe it because there are so many other variables to consider.
Please, can anyone tell me about the research on which this statement is based and, if possible, tell me where I might find the original reference?

Many thanks for your interest.
Ralph Rickards