In the 1880s a French agricultural engineer named Ringelmann was measuring how hard workers could push and pull a load. Groups were a side question. But his numbers showed something odd: the more people on the job, the less each one seemed to add.
In the figures that circulated for decades, through a 1927 German summary, one worker on a rope averaged 63 kilograms of pull. Three together managed 160, about two and a half times one person. Eight managed 248, less than four times. Ringelmann reported the work in 1913 and put the shortfall down mostly to coordination. People pulling together don’t all heave at the same instant. He allowed that motivation might also be involved.
For decades people cited the result, but nobody tried to repeat it. Then, in 1974, Ingham and his colleagues built an experiment to pull the two explanations apart.
First they repeated the rope pull with real groups and got a similar curve. Pairs pulled at 91% of what their members managed alone, groups of six at 78%.
Then the clever part. Each volunteer was blindfolded and put at the rope. They were told that others were pulling with them. In fact they always pulled alone, while confederates only pretended to pull. Every participant needed five pretend pullers, plus the experimenter.
With no one else pulling, there was nothing to fall out of time with. The volunteers still pulled less: about 90% of their solo effort when they believed one other person was on the rope, and about 85% with two to six.
Five years later, Bibb Latané, Kipling Williams and Stephen Harkins pointed out a possible flaw. Between turns, Ingham’s volunteers had stood watching the confederates, so the person pulling “alone” might have been playing to a larger audience. Their own version used shouting. Students wore blindfolds and headphones that played a recording of six people yelling, so nobody could hear anyone else, and the audience never changed. People who believed one partner was shouting with them shouted at 82% of their solo effort; with five, 74%.
For shouting, the team estimated that about half the shortfall came from poor coordination and half from people simply easing off. They called the second half social loafing.
Ringelmann himself had nearly disappeared by then. Latané’s paper described him as a German psychologist who never published his study. It took until 1986 for David Kravitz and Barbara Martin to find the original article, and the French engineer who wrote it.