Are We Smart Enough to Know How Smart Animals Are?(64)
We once applied a Menzel-type test to Socko, when he was still an adolescent chimpanzee. Through a small window, Socko watched my assistant hide an apple in a large tractor tire in the outdoor enclosure, while the rest of the colony was kept behind closed doors. Then we released the colony, holding Socko back until last. The first thing he did after coming out the door was to climb onto the tire and peek into it, checking on the apple. He left it alone, though, and nonchalantly walked away from the scene. He waited for more than twenty minutes, until everyone was otherwise occupied, and then went to collect the fruit. This was clever, since he might otherwise have lost his prize.
The truly interesting twist came years later, however, when we repeated this experiment. Socko had been tested only once, and we showed the video to a visiting camera crew. But as is typical, the crew trusted its own filming better and insisted on redoing the whole test. By this time Socko was the alpha male and hence could not be used anymore. Being of high rank, he would have had no reason to conceal what he knew about hidden food. So instead we selected a low-ranking female named Natasha and did everything nearly same. We locked up all the chimps and let Natasha watch through the window while we hid an apple. This time we dug a hole in the ground, put the apple into it, and covered it with sand and leaves. We did this so well that afterward we barely knew where we’d put the fruit.
After the others were released, Natasha finally entered the enclosure. We waited anxiously, following her with several cameras. She showed a pattern similar to Socko’s and moreover displayed a far better sense of location than we did. She passed slowly over to the precise hiding spot, then returned ten minutes later to confidently dig up the fruit. While she did so, Socko stared at her with apparent surprise. It is not every day that someone pulls an apple out of the ground! I worried that Socko might punish her for snacking right in front of him, but no, Socko ran straight to the tractor tire! He looked into it from several angles, but obviously it was empty. It was as if he had concluded that we were hiding fruit again—and he recalled the exact location we’d used before. This was most remarkable since I am pretty sure Socko had had only one experience of this kind in his whole life, which had occurred five years earlier.
Was this mere coincidence? It is hard to tell based on a single event, but fortunately a Spanish scientist, Gema Martin-Ordas, has been testing out this sort of memory. Working with a large number of chimpanzees and orangutans, she tested the apes on what they remembered of past events. Previously, the apes had been given a task that required them to find the right tool to fetch either a banana or frozen yogurt. The apes had watched tools being hidden in boxes, after which they needed to pick the right box to get a tool for the task. This being easy for apes, all went well. But three years later, after the apes had gone through scores of other events and tests, they all of a sudden encountered the same person, Martin-Ordas, presenting the same setup in the same rooms of the building. Would the presence of the same investigator and situation cue the apes about the challenge they faced? Would they know right away what tool to use and where to look for it? They did, or at least those with previous experience did. Na?ve apes did nothing of the kind, thus confirming the role of memory. And not only that, the apes did not hesitate: they solved the problem in a matter of seconds.3
Most animal learning is of a rather vague kind, similar to how I have learned to avoid some Atlanta highways at certain times of the day. Having gotten stuck in traffic often enough, I will look for a better, faster route, without any specific memory of what happened on my previous commutes. This is also how a rat in a maze learns to turn one way and not another, and how a bird learns at what time of day to find bread crumbs at my parents’ balcony. This kind of learning is all around us. What we deem a special kind, the one at issue here, is the recall of particulars, the way the French novelist Marcel Proust, in In Search of Lost Time dwelled on the taste of a petite madeleine. The little tea-soaked biscuit made him relive his childhood visits to Aunt Leonie: “No sooner had the warm liquid mixed with the crumbs touched my palate than a shudder ran through me and I stopped, intent upon the extraordinary thing that was happening to me.”4 The power of autobiographical memories lies in their specificity. Colorful and alive, they can be actively called up and dwelled upon. They are reconstructions—which is why they are sometimes false—yet so powerful that they are accompanied by an extraordinary sense of their correctness. They fill us with emotions and sensations, as happened to Proust. You mention someone’s wedding day, or Dad’s funeral, and all sorts of memories about the weather, the guests, the food, the happiness, or the sadness will flood the mind.
This kind of memory must be at work when apes react to cues connected to events from years back. The same memory serves foraging wild chimpanzees, which visit about a dozen fruit-bearing trees per day. How do they know where to go? The forest has far too many trees to go about it randomly. Working in Ta? National Park, in Ivory Coast, the Dutch primatologist Karline Janmaat found apes to have an excellent recall of previous meals. They mostly checked trees at which they had eaten in previous years. If they ran into copious ripe fruit, they’d gorge on it while grunting contentedly and make sure to return a couple of days later.
Janmaat describes how the chimps would build their daily nests (in which they sleep for only one night) en route to such trees and get up before dawn, something they normally hate to do. The intrepid primatologist followed the traveling party on foot, but whereas the chimps typically ignored her tripping or stepping on a noisy branch, now they all would turn around and stare pointedly at her, making her feel bad. Sounds draw attention, and the chimps were on edge in the dark. This was understandable since one of the females had recently lost her infant to a leopard.