Monkey see, monkey do – the truth underlying the proverb

"When in Rome, do as the Romans do!"

Nemo is two years old now and she tries to imitate her parents in what she says or does. She doesn't do it perfectly, but with every repetition, she only gets better and faster.

Cultural learning is an inherent part of being human. In fact, in addition to a genetic evolution, modern humans are also a result of cultural evolution. We, as a species, learned by observation - language, tool making, hunting, social skills, rituals; we passively learnt them all by being present in a community or a society and they in turn helped us evolve faster. We could store information outside ourself and we could learn from others without having to wait the changes in our inheritance.

In one of the least modest statements of intellectual history, Sigmund Freud considered his work on discovering the human unconscious as one of the three great revolutions in the history of science. The other two being - the Copernican revolution and Darwin’s theory of evolution. Despite this apparent lack of modesty, I do credit Freud for pointing out one salient commonality underlying these scientific revolutions, which is that they all knock human arrogance off its pedestal. They all destroy the vision of human uniqueness that has been cherished for centuries and is corrupting our thoughts even today.

However, by these standards, a couple of recent papers published in Science have heralded another scientific revolution – one that takes away the uniqueness of culture from human existence.

It began with a simple idea, proposed over half a century ago by the Japanese biologist Kinji Imanishi, that if animals, like humans can learn from each other, they will inevitably develop different behaviors in different groups, resulting in cultural variation within the same species. On the face of it – it is a simple idea and yet, it has been conclusively proven only now. There has long been a debate about animal culture that has focused on the mechanisms of behavioral transmission. Do animals learn from each other the way humans do? If yes, is this purely imitation or is this based on a goal directed approach? Is animal learning merely for genetic survival or is there a cultural evolution happening in the animal world?

Many studies in the past have looked at animal learning from human sources and have found little success. But this does not reveal much about animal learning from other members of the group. It is this specific question that these two papers have addressed in two different model species – the humpback whales and the Vervet monkeys.

     An example of the newer lobtail feeding technique wherein the whale pounds on the surface of the water with his fluke and causes greater clustering of the prey. B) A group of vervet monkeys being trained to associate taste with corn kernels.

In the first report, Allen et al, demonstrate the spread of a new hunting technique among humpback whales by cultural learning. Their observations are based on a large-scale study - spanning 27 years and 73,790 sightings of individually marked humpback whales - in the gulf of Maine where the sand lance (a popular prey) spawn.

Traditionally, humpback whales are seen to feed by producing air bubbles. Yes, air bubbles that drive the tiny prey fish together into large clusters, just under the surface of the water. The whales usually feed in large groups where one whale initiates the attack by blowing their large curtains of air bubbles that drive the prey together and the other whales then join the party with the gaping wide mouths. This allows the whales to gulp hundreds of water and the fish in them in a matter of seconds. However, in the year 1980, a whale was seen to do something different. This rebel whale was seen to whack the surface of the water with his fluke and the resulting noise further clumped the prey together. In contrast to bubble feeding, this new tactic was christened as lobtail feeding.

The authors then studied the spread and diffusion of this feeding technique across large populations of humpback whales. Their statistical tests showed that the spread of this technique was most significantly correlated to the time spent by the two whales together. Other possible alternatives like genetic spread of the behavior or individual learning by experience did not stand up to the same statistical scrutiny.

Spatial distribution of lobtail feeding

A network depicting the social network of whales sighted at least 20 times. Based on statistical analysis, the spread of the new feeding technique best correlated with the duration of contact between the individuals.

Although, this report is a good indication of cultural learning in animals, it does not establish the same conclusively.

The second study by Van de Waal et al, however, cleverly and elegantly overcame the limitations of this study and established similar principles of learning in Vervet monkeys.

Using four groups of wild vervet monkeys, the authors showed that animals from a group developed their preferences for a particular food source based on the other members of the group. The animals were first exposed to corn kernels of two different colors. For two of the groups, one color was palatable while the other was distasteful. The remaining two groups were trained to find the exactly opposite colors palatable. As part of this early exposure, all groups developed a preference for the untreated corn – which was marked by a different color in two of the groups. This observation is the standard paradigm of animal learning that we all encounter – where humans and animals learn from their experience and change future choices.

Interestingly, the investigators extended their study of color preferences to the next generation of new infants and to male immigrants from neighboring groups. This time however, the corn kernels were merely colored with no noxious taste associated with either color.  Interestingly, they found that 26 of the 27 newborn infants also developed a preference for the corn color that was preferred by the group. The behavior of these infants including that of the outlier, established that food preferences were acquired from the mothers and not through individual exploration.

Males abandon the food preference learned in their home group in favor of the local preference of the adopted group. Column colors indicate the food preference of each male in the original group and the contrasting food choice in the adopted group. The color of the framing line indicates the color preference of the adopted group as a whole. The (*) indicates the color eaten first in the adopted group when not outranked by local residents.

It was even more fascinating that the male immigrants originating from groups with opposite color preferences also adopted the local preferences, without any exposure to noxious stimuli. This clearly shows that the monkeys are culturally sensitive to the behavior of the locals and are more likely to adopt them even though their own experience may suggest the contrary.

Both these studies ingeniously demonstrate the existence of culture in animal societies, thus destroying the last uniquely human pedestal.

Slobodkina’sfairy tale of a cap peddler trying to recover his wares from a troop of monkeys was a rather popular tale for many kids. But these studies now suggest that such a piece of fiction may not be very far from the truth – at least in the case of Vervet monkeys and whales.