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| ©2017, Siegfried Woldhek |
In the adjacent control room, a rhesus macaque that has just begun his daily routine can be seen on a small black-and-white screen. His name is Yko. He is operating a joystick while simultaneously watching a screen and sucking on a straw. The grainy black-and-white image on the monitor in the control room reminds me of the film and photographic material of the first experimental space flights. As a child I saw images of a rhesus macaque in a space suit buckled into a chair, passively awaiting what was to come. But Yko isn’t waiting: he’s playing a computer game with great enthusiasm.
A second screen shows a close-up of the large, clear eyes and the expressive eyebrows of the rhesus macaque at play. A small white cross on his black pupil confirms that the eye tracking system is effortlessly following the direction of his eyes. His eyes dart back and forth in pursuit of the figures on the computer screen. The figures appear in different positions on the screen and in different colors and sizes. Yko operates the joystick deftly, first toward one figure, then toward the other. He has learned how he is supposed to move the joystick – after hearing a short sound, in the direction of a blue circle; after hearing a long sound, in the direction of an orange circle.
Children play similar games to score points and reach higher levels. In this laboratory, the rhesus macaques do everything for a reward in the form of Tang, an orange drink also popular among Mexican children. It is in a laboratory bottle high up on a shelf in the corner of the testing area. A precise amount is released at a constant rate via a dosing system and offered to the rhesus macaque through a straw. The click of the dosing pump in the control room is heard whenever the correct answer is given, which is – after Yko gets the hang of it – about every ten seconds.
The rhesus macaque who will likely take part in our new listening experiment is not new to testing. He is seven years old now, but was two years old when the laboratory purchased him from a North American laboratory. His name is Capi, an abbreviation for El Capitán (The Captain), because he often holds his hand to his eyebrow as if saluting. It turns out he has risen to the rank of alpha male in a group of four rhesus macaques that perform behavioral tasks for three or four hours a day. Every morning they are weighed and taken to the testing area, and, at the end of the afternoon, they are returned to their sleeping quarters. At night the light is switched off and in the morning it is switched on again.
Structure and regularity define the life of the rhesus macaques, as they do the life of all the primates in the laboratory. The working day for everyone lasts from 8:00 A.M. to 8:00 P.M. on weekdays, with a lunch break at about 3:00 P.M., and from 8:00 A.M. to about 2:00 P.M. on Saturdays. Sunday is the only free day. The two students who take turns picking me up at a nearby hotel confided in me earlier that they find their work regime too strict, leaving them little time to see friends or family.
Today Capi will be shaved because his coarse hair makes it difficult to perform an electroencephalogram (EEG). While a dab of conductive gel and an adhesive plaster will suffice for a human, an electrode slips off a rhesus macaque at the slightest movement. Ramón uses a bright blue disposable razor to shave Capi’s right ear, to which the reference electrode will be attached later. Slightly sedated by the ketamine, Capi undergoes the shaving passively. It is both an endearing and a distressing sight. His ear is being shaved because I want it, not he.
It is the first time I have been able to observe Capi at close quarters without him becoming agitated by my presence. Though you can see from his facial muscles that he is still a bit drowsy, he follows every movement made around him. The soft white hairs on his ear are easily shaved off. And after the coarser, green-yellow hair is removed from his scalp, only a downy white layer remains, thin enough to allow the EEG electrodes to be attached later using some medical tape.
The skull of a rhesus macaque is not only much smaller than I had imagined but also much flatter, almost like that of an adult cat. Hugo shows me a piece he has removed from another rhesus macaque. It is a piece of the crown the size of a small matchbox. A tiny segment of bone has to be removed for the measurement method commonly used in such laboratories. This involves inserting several electrodes into the brain using a catheter.
Sitting as calmly as ever in his chair, Capi, with his bony little head, reminds me a bit of Paco, my one-time Siamese cat. I have to stop myself from giving him a little pat on his head.
As expected, the effect of the analgesic wears off quickly. Capi’s big eyes are as alert as ever, and his mouth with its sharp eyeteeth has tightened up again. It’s not for nothing that Ramón wears leather gloves when leading Capi from his cage to his chair.
I take a seat next to Capi at eye level and address him in a friendly tone, the way I would a cat or a small child. It quickly becomes clear that this isn’t a good idea. Capi responds with anxious growling noises. Startled, I take a few steps back. Ramón laughs at my reaction, reassuring me it’s not my friendly words that have upset Capi but my direct stare."
[Provisional translation (©2018 Sherry Macdonald) of a fragment from Darwins vermoeden, expected to be published in the Summer of 2018 by Nieuw Amsterdam, and in the Winter of 2018 by MIT Press.]
