How does intelligence benefit mammals

Human babies start passing the test around their first birthdays—but most animals, even chimps, fail. The ones that pass are typically domesticated mammals.

Dogs are especially good at it. The "mirror test" checks for self-awareness. Recognizing oneself in a mirror is considered to be a sign of cognition, as doing so requires at least a rudimentary concept of identity. Unfortunately, when measuring these capacities in animals, it is often difficult to achieve the sample sizes and conditions required for scientific accuracy.

A study found that elephants pass the pointing test about two-thirds of the time. An extreme example of such a design flaw is that Kandula, the elephant who used a stool, was initially given a stick for the purpose of batting down the food. However, elephants locate food with their sense of smell. This is analogous to humans with eyes on their hands being told to use silverware. The pointer and mirror tests might also be ecologically inconsistent.

Irene Pepperberg, an animal psychologist at Harvard who works with parrots, explains, "Mirror tests check whether a subject has self-recognition, but the test can be tricky.

We gave the mark-test to one of my parrots. He saw the mark in the mirror, scratched at it for a couple of seconds, the mark didn't go away, and he walked off. Parrots get gunk on their faces all the time when they feed, so what did the bird's actions mean? Ditto for the point test: If an animal doesn't have arms, hands, and fingers, what would pointing really mean?

Therein lies a paradox: Scientists have difficulty accrediting experiments that are not properly controlled, but, with animals, properly controlled studies often cannot account for ecological context because animals would never encounter laboratory conditions in the course of their natural lives.

This is why the field still relies mostly on anecdotes. It follows that, with the current infrastructure, analyzing animal intelligence is nearly impossible. Perhaps with more funding, more complex studies could be done at a greater scale. Earlier this year, the Duke Canine Cognition Center was able to organize a study of animals across 36 species for an assessment similar to the pointer test.

The center has also built a network of over a thousand dogs on which they can conduct experiments. Brian Hare, a founder of the center, says his goal is to build a database large-enough to shed light on longstanding questions about behavior, breeding, and genetics.

Adam Pack, who studies dolphins at the University of Hawaii, explained in an email that researchers rely primarily on funding from the National Science Foundation and that many will set up nonprofit arms to enable donations from family foundations and philanthropic individuals. The animals at Suaq ply their tools for two major purposes. First, they hunt for ants, termites and, especially, honey mainly that of stingless bees --more so than all their fellow orangutans elsewhere.

They often cast discerning glances at tree trunks, looking for air traffic in and out of small holes. Once discovered, the holes become the focus of visual and then manual inspection by a poking and picking finger. Usually the finger is not long enough, and the orangutan prepares a stick tool. After carefully inserting the tool, the ape delicately moves it back and forth and then withdraws it, licks it off and sticks it back in.

Most of this manipulation is done with the tool clenched between the teeth; only the largest tools, used primarily to hammer chunks off termite nests, are handled. The second context in which the Suaq apes employ tools involves the fruit of the Neesia. This tree produces woody, five-angled capsules up to 10 inches long and four inches wide. The capsules are filled with brown seeds the size of lima beans, which, because they contain nearly 50 percent fat, are highly nutritious--a rare and sought-after treat in a natural habitat without fast food.

The tree protects its seeds by growing a very tough husk. When the seeds are ripe, however, the husk begins to split open; the cracks gradually widen, exposing neat rows of seeds, which have grown nice red attachments arils that contain some 80 percent fat.

To discourage seed predators further, a mass of razor-sharp needles fills the husk. The orangutans at Suaq strip the bark off short, straight twigs, which they then hold in their mouths and insert into the cracks.

By moving the tool up and down inside the crack, the animal detaches the seeds from their stalks. After this maneuver, it can drop the seeds straight into its mouth. Late in the season, the orangutans eat only the red arils, deploying the same technique to get at them without injury. Both methods of fashioning sticks for foraging are ubiquitous at Suaq. In general, fishing in tree holes is occasional and lasts only a few minutes, but when Neesia fruits ripen, the apes devote most of their waking hours to ferreting out the seeds or arils, and we see them grow fatter and sleeker day by day.

We doubt that the animals at Suaq are intrinsically smarter: the observation that most captive members of this species can learn to use tools suggests that the basic brain capacity to do so is present.

So we reasoned that their environment might hold the answer. The orangutans studied before mostly live in dry forest, and the swamp furnishes a uniquely lush habitat. More insects make their nests in the tree holes there than in forests on dry land, and Neesia grows only in wet places, usually near flowing water. Tempting as the environmental explanation sounds, however, it does not explain why orangutans in several populations outside Suaq ignore altogether these same rich food sources.

Nor does it explain why some populations that do eat the seeds harvest them without tools which results, of course, in their eating much less than the orangutans at Suaq do. The same holds for tree-hole tools. Occasionally, when the nearby hills--which have dryland forests--show massive fruiting, the Suaq orangutans go there to indulge, and while they are gathering fruit they use tools to exploit the contents of tree holes.

The hill habitat is a dime a dozen throughout the orangutans geographic range, so if tools can be used on the hillsides above Suaq, why not everywhere? Another suggestion we considered, captured in the old adage that necessity is the mother of invention, is that the Suaq animals, living at such high density, have much more competition for provisions.

Consequently, many would be left without food unless they could get at the hard-to-reach supplies--that is, they need tools in order to eat. The strongest argument against this possibility is that the sweet or fat foods that the tools make accessible sit very high on the orangutan preference list and should therefore be sought by these animals everywhere. For instance, red apes in all locations are willing to be stung many times by honeybees to get at their honey.

So the necessity idea does not hold much water either. A different possibility is that these behaviors are innovative techniques a couple of clever orangutans invented, which then spread and persisted in the population because other individuals learned by observing these experts.

In other words, the tool use is cultural. A major obstacle to studying culture in nature is that, barring experimental introductions, we can never demonstrate convincingly that an animal we observe invents some new trick rather than simply applying a well-remembered but rarely practiced habit. Neither can we prove that one individual learned a new skill from another group member rather than figuring out what to do on its own. Although we can show that orangutans in the lab are capable of observing and learning socially, such studies tell us nothing about culture in nature--neither what it is generally about nor how much of it exists.

So field-workers have had to develop a system of criteria to demonstrate that a certain behavior has a cultural basis. First, the behavior must vary geographically, showing that it was invented somewhere, and it must be common where it is found, showing that it spread and persisted in a population. The tool uses at Suaq easily pass these first two tests. The second step is to eliminate simpler explanations that produce the same spatial pattern but without involving social learning.

We have already excluded an ecological explanation, in which individuals exposed to a particular habitat independently converge on the same skill. We can also eliminate genetics because of the fact that most captive orangutans can learn to use tools. The third and most stringent test is that we must be able to find geographic distributions of behavior that can be explained by culture and are not easily explained any other way. One key pattern would be the presence of a behavior in one place and its absence beyond some natural barrier to dispersal.

In the case of the tool users at Suaq, the geographic distribution of Neesia gave us decisive clues. Neesia trees and orangutans occur on both sides of the wide Alas River. In the Singkil swamp, however, just south of Suaq and on the same side of the Alas River [ see map on opposite page ], tools littered the floor, whereas in Batu-Batu swamp across the river they were conspicuously absent, despite our numerous visits in different years.

In Batu-Batu, we did find that many of the fruits were ripped apart, showing that these orangutans ate Neesia seeds in the same way as their colleagues did at a site called Gunung Palung in distant Borneo but in a way completely different from their cousins right across the river in Singkil. Batu-Batu is a small swamp area, and it does not contain much of the best swamp forest; thus, it supports a limited number of orangutans. We do not know whether tool use was never invented there or whether it could not be maintained in the smaller population, but we do know that migrants from across the river never brought it in because the Alas is so wide there that it is absolutely impassable for an orangutan.

Where it is passable, farther upriver, Neesia occasionally grows, but the orangutans in that area ignore it altogether, apparently unaware of its rich offerings. A cultural interpretation, then, most parsimoniously explains the unexpected juxtaposition of knowledgeable tool users and brute-force foragers living practically next door to one another, as well as the presence of ignoramuses farther upriver.

To look into this question, we first made detailed comparisons among all the sites at which orangutans have been studied. We found that even when we excluded tool use, Suaq had the largest number of innovations that had spread throughout the population. This finding is probably not an artifact of our own interest in unusual behaviors, because some other sites have seen far more work by researchers eager to discover socially learned behavioral innovations. We guessed that populations in which individuals had more chances to observe others in action would show a greater diversity of learned skills than would populations offering fewer learning opportunities.

The relative range compared to other species remains to be evaluated. Several other factors could be incorporated into a model of intelligence: 1 Analysis of cognitive representation in addition to measurement of stimulus features can provide insight to the way animals make connections.

For example, showing that a dolphin can identify visually an object that has previously only been identified through audition and vice-versa indicates a representation independent of modality.

In this case, we are talking about more than just a learning set type of experiment but rather the changes that occur over days, weeks, and years showing learning built on previous experiences.

Many researchers report anecdotally that marine mammals who engage in years and decades of cognitive work improve in their ability to learn new test procedures over time.

Such long-term growth and change are fundamental to our understanding of human intelligence, and the long developmental course of many marine mammals suggests extended neural and behavioral plasticity, as seen in humans. There is now some evidence that behavioral plasticity is, indeed, adaptive Ducatez et al. If flexibility and the knowledge attainment it supports are adaptive, then they are subject to evolutionary pressures and will necessarily vary across species.

It is possible that comparative psychologists have unintentionally gone out of their way to ignore these factors by focusing study on naive animals placed in impoverished contexts; this method might squelch our ability to find differences across species and between individuals.

One of the big problems of marine mammal behavioral research is the length of time it takes to collect data with all its attendant costs, small sample sizes, and limits on questions to be asked. Alternatively, good estimates of visual acuity can be determined from measures of retinal ganglion cell density and axial length of the eye Mass and Supin, , measurements that can be quickly made post-mortem.

Good audiogram approximations can be made through evoked potential techniques in less than an hour Finneran and Houser, As neural function and organization measurement improves, we may be able to explore valid cognitive characteristics through widely available anatomical techniques like post-mortem DTI.

This is certainly something that animal trainers encounter, when they find major differences in trainability among subjects, although it may not be something that is formally assessed and reported. Variability in intelligence among individuals might reflect the cognitive flexibility of a species better than a static measure of average performance.

Just because comparative psychologists have yet to successfully characterize and delineate all the processes and situations that govern animal thought and behavior does not mean that there are not significant differences in how animals gather information in the world, process it, and act on it across multiple contexts. As indicated here, there are numerous comparisons we could make that might be more fruitful for delineating differences in intelligence than the foundational processes targeted by Macphail.

Clearly, these foundational processes exist, but they are recruited differentially across species as their ecologies drive shifts in other systems e. Marine mammal species transitioned, over the course of evolutionary history, between markedly different ecological settings, and continue to transition between these settings on a daily basis.

These transitions may have promoted neural, sensory, and cognitive flexibility reflected in their behavior in the wild and in the laboratory.

As long-lived animals who perform well in experimental settings, they are excellently situated to provide insight into the link between ecological and cognitive flexibility and how this may bear on a comparative understanding of intelligence.

All parts of the manuscript reflect a group effort with the exception of The Brain, which was written primarily by PC. All authors contributed to the article and approved the submitted version. The remaining authors declare that the research was conducted in the absence of any commercial conflicts of interest. Abramson, J. Relative quantity judgments in South American sea lions Otaria flavescens.

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