Cómo abre un tubo un chimpancé

Un exhaustivo experimento demuestra la habilidad humana del aprendizaje social

JUAN GÓMEZ - Berlín - 07/09/2007, El País

Los primates no humanos no acumulan conocimiento. Los humanos sí, a través del aprendizaje social. Las diferencias entre las habilidades humanas de aprendizaje social y las de los grandes primates se demuestran por primera vez de forma exhaustiva en un estudio del Instituto Max Planck de Antropología Evolutiva que publica hoy la revista Science.

El investigador español Josep Call y su colega Esther Herrmann explicaron ayer en Berlín cómo ocho años de experimentos con unos 230 sujetos -100 niños de dos años y medio, 100 chimpancés y 30 orangutanes- les llevaron a conclusiones que pueden sorprender a los legos en teoría evolutiva y comportamiento animal: el mono improvisa y se enfrenta a los problemas con creatividad -algo roma-, mientras que los niños tienden a remedar los comportamientos que ven.

Un problema típico sería un tubo de plástico que encierra comida. El chimpancé tratará de abrirlo por la fuerza, le dará vueltas, lo morderá y lo golpeará. El niño busca la solución imitando a quien le quede cerca. Si es otro humano que le demuestra la habilidad de abrir el tubo, el niño lo abrirá también por el mismo método. Si está a solas con un mono, lo más probable es que el niño muerda, golpee y trate de abrir el tubo por la fuerza. A los dos años y medio, la aptitud física de los humanos es similar a la de los chimpancés. Sin embargo, los niños superaron correctamente el 74% de las pruebas propuestas por los investigadores cuando éstos les mostraban la solución. Los chimpancés y los orangutanes, sólo el 33%.

El cerebro humano es tres veces mayor que el de los chimpancés. Es una ventaja obvia, que a los investigadores -entre ellos María Victoria Hernández-Lloreda, de la Universidad Complutense de Madrid- no les explica, sin embargo, la mayor inteligencia humana, su capacidad de abstracción y de adaptación. La inteligencia social de la que el hombre dispone ahorra tiempo de aprendizaje y energía. Así, los humanos no tienen que descubrir de nuevo las habilidades que necesitarán en el curso de sus vidas.

Call enarbolaba ayer un sencillo abrebotellas para ilustrarlo. "Ningún ser humano del mundo podría aprender por sí mismo todas las habilidades que se necesitan para fabricar una cosa tan simple como ésta: las aleaciones del metal, las máquinas para la producción, el diseño". Call defiende la hipótesis de que un solo mono, por el contrario, sí que puede aprender por sí mismo todos los comportamientos y habilidades que dominan sus congéneres en la naturaleza. Otro ejemplo al que recurrió Call es el álgebra, que no existió hasta hace poco más de mil años. Su conocimiento se ha extendido a pesar de ello en todo el mundo mediante la enseñanza. Es improbable que pudiera reinventarse por cada generación.

Mantiene el investigador la hipótesis de que los seres humanos desarrollaron estas habilidades por su nomadismo ancestral. Según el científico, "el desarrollo de habilidades sociales facilita el reconocimiento grupal entre individuos aun cuando están rodeados de extraños". Los chimpancés viven en grupos sociales de cierta complejidad y usan signos poco complejos para comunicarse. Sin embargo, apenas abandonan su grupo durante toda su vida, de modo que no necesitan construir frente a extraños su identidad social.

Un niño de dos años es más inteligente que un mono por el entorno cultural

Madrid. (Efe).- Un simio es capaz de hacer pequeñas sumas y de usar herramientas que un niño de dos años no sabe ni cómo coger, pero el pequeño es desde esa edad ya más inteligente por haber aprendido culturalmente a interpretar intenciones y a imitar a los adultos para resolver un problema, no porque tenga un cerebro más grande.

Es decir, la inteligencia humana se debe a una especialización de la cultura, y no a una inteligencia general asociada al mayor tamaño cerebral, según una investigación realizada durante los últimos cuatro años por un equipo internacional en el que han participado los españoles Josep Call y Victoria Hernández-Lloreda. Hernández-Lloreda explicó que para su investigación, que mañana publica la revista Science, se ha aplicado "una amplia batería de tests cognitivos" a 106 chimpancés y 32 orangutanes, y a 105 niños de 2 años de edad.

Para igualar las condiciones de aplicación de los tests a las diferentes especies llegaron a poner una barrera de plexiglás entre quien realizaba las pruebas y el niño, a fin de simular el mismo entorno en el que se hacían a los simios. Los dos obtuvieron resultados muy similares en los tests relativos al conocimiento del mundo que les rodea, e incluso los chimpancés mejor que los niños en operaciones de rotación, sumas de pequeñas cantidades y uso de herramientas.

Sin embargo, los pequeños, lejos aún de la edad de escolarización en la que aprenden a contar y a leer, tuvieron mejores resultados en tareas relacionadas con la comprensión del mundo social. Si los niños simplemente tuvieran más inteligencia general que los grandes simios, se deberían haber encontrado diferencias sistemáticas en todas las áreas, pero no fue así. Las mayores capacidades de los niños en cognición y aprendizaje social a esa edad, cuando aún sus capacidades de cognición física son como las de los grandes simios, sugieren una adaptación biológica específica para la vida social y la cultura.

A partir de esas habilidades están preparados para adquirir otras más complejas y gran cantidad de información a través tanto de la imitación como de la instrucción. Sin esas capacidades socio-cognitivas los niños avanzarían muy poco con respecto a los grandes simios en sus capacidades matemáticas, por ejemplo, ya que no podrían utilizar los símbolos numéricos, explicó Hernández-Lloreda, profesora del departamento de Metodología de Ciencias del Comportamiento de la Universidad Complutense de Madrid (UCM).

Por lo tanto, son las habilidades socio-cognitivas las que dan la clave para entrar en el mundo de la cultura, y crecer dentro de un grupo cultural permite a los niños beneficiarse de las habilidades y el conocimiento adquiridos por el resto de la especie, acceder al uso de herramientas y símbolos, incluido el lenguaje, que otros ya han desarrollado.

El experimento, para el que Hernández-Lloreda elaboró el desarrollo psicométrico de la batería de tests, se realizó en el instituto Max Plank de Antropología Evolutiva de Leipzig (Alemania), donde trabaja Call, que es además codirector del Wolfang Köhler Primate Research Center. El trabajo se enmarca en una colaboración entre el instituto Max Plank y la Universidad Complutense, que comenzó en 2003 y se formalizó con un convenio de colaboración hace dos años entre la institución alemana y el grupo de estudio de las relaciones sociales de la UCM del que forma parte Hernández.

La Vanguardia, 06/09/2007

Fair Testing of Apes

Comment by Frans B. M. de Waal, Ph. D., Director, Living Links, EMORY University


This study claims that apes have equal technical but lower social intelligence than human toddlers. Although it is an impressive battery of tests, and an impressive data analysis, there is a glaring lack of equivalence between the way the children and apes have been tested, one that has been criticized before by others and myself.

It may seem that testing all subjects in the same way is fair and equal, but the children are tested by their own species (a human model), whereas the apes are tested by a stranger of another species (a human model). It is entirely possible that this doesn't make much difference in physical tasks, which after all focus on physical objects, but we do know that it makes a huge difference in relation to social tasks, which by definition focus on the interaction between subject and experimenter.

It is easier to process social information of one's own species. So, it is only seemingly that all subjects were tested in the same way.

Here at the Living Links Center we have in the past five years conducted many tests, which demonstrate that if chimpanzees are tested with their own kind they show impressive social learning. We have specialized in chimp-to-chimp testing precisely to circumvent the confound introduced by the human tester.

Examples can be found on the website of Living Links:
http://www.emory.edu/LIVING_LINKS/diffus.html
http://www.emory.edu/LIVING_LINKS/conform.html

Our results don't fit the "cultural intelligence" hypothesis mentioned in the study, and in fact they contradict the central claim of this new study, because they demonstrate that apes are very good at social tasks. Testing apes with models of their own species takes more time and patience, hence is harder to integrate in a large battery of tests, but it is ecologically more relevant (that is, it relates more closely to the context in which primate cognition evolved, which is of course among members of the same species).

So, unless I see more evidence, my conclusion is that all that this new study demonstrates is how cognitive performance is sensitive to who does the testing: one's own or another species.

Babies and Chimps Compete in Mental Olympics

September 7, 2007, 1:13 pm

By Mike Nizza

Tags: intelligence, wildlife

While The Lede considered Man versus Machine, scientists were studying another historic duel: Baby versus Chimp.

106 chimpanzees, 32 orangutans and 105 humans who were about 2.5 years old were put through “The Primate Cognition Test Battery,” which includes 16 tasks divided between physical and social cognition. Here’s how the authors of the study in the journal Science described the difference:

Physical cognition deals with inanimate objects and their spatial-temporal-causal relations, whereas social cognition deals with other animate beings and their intentional actions, perceptions, and knowledge.

Now brace yourselves, human readers: The babies did not trounce the apes. In fact, chimpanzees scored more correct responses in the tests on causality and just about tied on spatial skills, according to this chart.

But the social learning tests were a rout for the babies, with chimpanzees way behind and orangutans apparently shut out. Reuters outlines how one social learning test went:

A researcher showed the children and apes how to pop open a plastic tube to get food or a toy contained inside. The children observed and imitated the solution. Chimpanzees and orangutans, however, tried to smash open the tube or yank out the contents with their teeth.

Despite the mixed results, Time magazine sounded uplifted. After all, the results suggested that we are special because we “cooperate and share expertise.” And that’s what “has allowed us to build complex societies, collaborate and learn from each other at a high level.”

Why did the monkey pee on his feet?

Published online: 7 September 2007; | doi:10.1038/news070903-18

Study helps to answer question of odd primate behaviour.

Matt Kaplan

Monkey pee: rubbing urine on the hands could be a way of seeking attention. Katalin Laszlo

It may seem strange, but many monkeys wash their hands and feet with urine. Researchers now think they know why.

Since this odd behaviour was first observed, explanatory theories have varied wildly from suggesting that it helps monkeys improve their grip when climbing to saying it is a method of cleaning. One widely supported theory argues that monkeys use urine washing to cool themselves down when temperatures get too high.

But new research hints that it's all about social communication.

The notion of animals using chemical scents to communicate with each other is hardly new. Dogs classically use urine to mark their territory, for example, as do many other creatures. But when it comes to peeing on oneself, researchers had thought physiological reasons might be as important as social ones. It seems they were wrong.

Hot times

Primatologist Kimran Miller and her research colleagues at the National Institutes of Health Animal Center in Poolesville, Maryland, monitored capuchin monkeys for ten months in a captive environment. The researchers would record daily the enclosure temperature and humidity and then note rates of urine washing. Their report, to be published in the American Journal of Primatology, shows that urine washing behaviours did not change with either temperature or humidity.

Instead, Miller and her team noticed a link between urine washing and attention-seeking.

Alpha males, for example, doubled their urine washing rates when being solicited by females. The researchers think this might be how males encourage females to continue paying attention once they've started.

And in 87% of fights or aggressive incidents, the loser of the battle washed in urine. The team suspects that this is also an attention-seeking behaviour — in this case seeking sympathy. But more research is needed to be sure.



"This really challenges the dominant theory that urine washing in capuchins is related to thermoregulation," comments primatologist James Anderson at the University of Stirling in Scotland.

"We see antelope that pee on their throats, vultures that poop on their feet, and monkeys that wash their hands in urine," says behavioural endocrinologist Fred Bercovitch at the centre for Conservation and Research for Endangered Species in San Diego. "It's obvious that urination is about more than elimination and it is great to see research like this that is figuring out why."

Social skills help toddlers outstrip apes in intelligence tests

• Sarah Knapton
• The Guardian
• Friday September 7 2007

Apes may be our closest relatives in the animal world, but in the battle of wits human toddlers are walking tall while their hairy ancestors are still dragging their knuckles.

In a study comparing the abilities of two-year-olds with chimpanzees and orang-utans, children surpassed the apes in social learning skills, researchers found. The findings are likely to lend further credence to the theory that higher social ability is a uniquely human trait, setting us apart from other primates.

Some 105 youngsters and 138 apes were subjected to a battery of cognitive tests over a two-week period during the study. The researchers found that the children were far more advanced than the apes in understanding nonverbal communications, copying solutions to a problem and understanding the intentions of others.

Esther Herrmann, of the Max Planck institute for evolutionary anthropology in Leipzig, Germany, who led the study, said: "This is the first time that anything like this has been done. We compared three species to determine which skills and abilities are distinctively human.

"Social cognition skills are critical for learning. Young human children who had been walking and talking for about one year, but who were still several years away from literacy and formal schooling, far outstripped both chimpanzees and orang-utans on tasks of social cognition."

In one learning test, human children and apes were shown how to pop open a plastic tube to get food or a toy contained inside. While the children watched and imitated the solution, the baffled chimps and orang-utans, tried to smash open the tube or yank out the contents with their teeth.

The toddlers were also better at following an adult's gaze and at pointing towards a cup containing a reward.

Human brains are three times bigger than those of the closest primate relatives. The researchers believe the results could provide crucial insight into cognitive evolution since the human and chimp family trees diverged around 6m years ago. Chimpanzees are considered the closest genetic relatives to humans, with orang-utans slightly more distantly related.

The apes, which performed the tests in animal sanctuaries in Africa and Indonesia, were closer to the toddlers in tests measuring "physical cognitive skills" involving things such as quantities, the researchers reported in the study published in the journal Science.

In the same journal, other researchers said they showed that apes and monkeys possessed skills such as guessing the intentions of others.

They studied cotton-top tamarins, rhesus macaques and chimpanzees.

Tots More Socially Cognitive Than Apes

By LAURAN NEERGAARD

WASHINGTON (AP) — Toddlers may act up like little apes, but researchers who compared the species concluded a 2-year-old child still has the more sophisticated social learning skills.

In one test, preschoolers who wanted a toy hidden in a trick tube intently copied a scientist's movements to retrieve the prize. Chimps watched the lesson, but then mostly tried to smash or bite open the tube. When it came to simple math, however, the apes seemed to know more than the youngsters, apparently "adding" how many tasty raisins researchers had hidden.

In a novel study, scientists lured 106 chimpanzees, 32 orangutans and 105 toddlers to sit through five hours of testing over several days. Researchers were trying to tell which innate abilities are distinctly human.

"Human children are not overall more intelligent than other primates, but instead have specialized skills of social cognition," concluded the lead researcher, Esther Herrmann of Germany's Max Planck Institute for Evolutionary Anthropology. "They learn in a way that chimpanzees don't learn."

But the findings, published in Friday's edition of the journal Science, conflict with other research that suggests the great apes, humans' closest relatives, are quite good at social learning, too. In fact, a second study in the same journal suggests chimps and monkeys have some capacity to infer someone's intentions by their actions. That is pretty complex, human-like thinking.

In that work, the animals sought out food containers that a researcher had grasped purposefully, not just tapped, or a container that he had touched with his elbow when his hands were full, but not one elbowed when his hands were empty.

The chimps and monkeys expected someone to behave rationally and adjusted their own actions accordingly, according to the lead researcher, Justin Wood of Harvard University.

"That shows quite a subtle social understanding going on in these animals," said Dr. Frans de Waal of Emory University's Yerkes National Primate Research Center, a well-known expert in primate cognition who was not involved in the research published Friday.

Comparing innate abilities can shed light on the evolution of human cognition.

Rather than studying one ability at a time, Herrmann and colleagues devised a battery of tests that they administered to 2 1/2-year-old children and to apes in wildlife sanctuaries in Uganda, Congo and Indonesia.

The apes and children fared equally well on tests of how they understood their physical world. Occasionally, apes did better.

For example, chimps and preschoolers could tell at a glance which dish contained a few more raisins. But when the dishes were covered and extra raisins dropped in, the apes kept better track of which dish had more.

Herrmann speculated that perhaps everyone starts out with ape-level math skills that humans surpass upon learning to count.

Then she tested social learning — communication, imitation and gauging intent from behavior. For example, Herrmann hid a treat under one of three cups and pointed to the right one. Preschoolers were much better at knowing to follow her gestures.

Overall, the preschoolers accomplished social-learning tasks correctly 74 percent of the time, while the apes did only 33 percent of the time.

Herrmann concluded that backs one theory of the evolution of human cognition, that specialized social skills more than general intelligence explain why humans learn more, in complex cultural groups, than do other primates.

But to de Waal, the preschoolers just had to imitate another human to pass these tests, while the apes had to imitate a stranger of another species, a higher hurdle.

Herrmann chose orphaned apes raised around humans to minimize those concerns.

Other studies have found that chimps pass similar social-learning tests when they know the human tester well or when a fellow chimp is trained to administer the tests, which is the method Yerkes now uses.

Recall the trick tube that Herrmann's apes could not open right? De Waal trained two chimps from different families to open a trick box in different ways and then sent them home. Later, their relatives mostly opened the box the way their matriarch had been trained, similar to human cultural learning.

Social learning is "maybe not as a perfect as in humans, but it's very well-developed," de Waal said.