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The most damaging phrase in the language is: “It’s always been done that way.”

~ Grace Hopper

Ever come across the five monkeys and a ladder thought experiment? If not, stick around. This is going to be an interesting post. If nothing else, it’s a modern-day parable.

People usually fail to mention this is actually a thought experiment and pass it off as a real experiment. It’s not. It’s a thought experiment based on an actual experiment published in a 1967 paper by a researcher called G.R. Stephenson (cited below), and it goes like this:

Five monkeys were placed in a cage. In the middle of the cage there was a ladder with a banana on top. As one might expect one of the monkeys raced toward the ladder and as he started to climb, the researchers sprayed the monkey with cold water. In addition to the monkey climbing the ladder, however, the four monkeys at the bottom of the ladder were also sprayed with ice cold water.

A second monkey attempted to climb the ladder and the same thing happened: the researchers sprayed all 5 monkeys with cold water. After a while none of the monkeys dared to climb the ladder to get their hands on the delicious banana, regardless of the temptation.

Once the researchers made sure none of the monkeys was going to climb the ladder, they replaced one of them with another monkey. The newcomer, unaware of the situation, ran toward the ladder to get the banana. But once he started to climb the ladder he was brought down and beaten up by the other four monkeys. After several beatings, the inexperienced new guy learned his lesson: Climbing = Getting beat up. Although he had absolutely no idea why.

The researchers then replaced another one of the original monkeys with an inexperienced one. The same thing happened again: newcomer climbs -> the other four beat him up -> he learns his lesson. The interesting observation here was that the first substituted monkey also joined in to beat up the the new guy, even though he had no idea why he was beaten up for doing the same thing.

The same process was repeated and the 3rd and 4th monkeys were substituted, only for the newcomers to get beaten up every time they attempted to climb the ladder until they stopped trying. Finally, the 5th monkey – the last of the original monkeys and the only monkey present in the cage who actually received the cold showers – was replaced. The new monkey, naturally, attempted to climb the ladder for the banana, but the other 4 monkeys – who had never received cold showers and were instead beaten up every time they tried to climb the ladder themselves – attacked the newcomer and beat him up.

If monkeys could speak English, the new guy would probably ask “Why do you guys keep hitting me every time I try to get the banana?“, and the other four monkeys, after giving each other puzzled looks, would reply “It’s always been done like this“.

Does it ring a bell?



Stephenson, G. R. (1967). Cultural acquisition of a specific learned response among rhesus monkeys. In: Starek, D., Schneider, R., and Kuhn, H. J. (eds.), Progress in Primatology, Stuttgart: Fischer, pp. 279-288. (Can’t find this one online. Of all the socially important research papers, this is the one not on the web.)

Mentioned in: Galef, B. G., Jr. (1976). Social Transmission of Acquired Behavior: A Discussion of Tradition and Social Learning in Vertebrates. In: Rosenblatt, J.S., Hinde, R.A., Shaw, E. and Beer, C. (eds.), Advances in the study of behavior, Vol. 6, New York: Academic Press, pp. 87-88