Few remember the second chimp launched into space by the United States. Even fewer remember the terrible equipment malfunction that subjected the animal to 76 electric shocks in orbit.
The chimps of space -- Ham, the first primate in space, and Enos, the second primate (after Yuri Gagarin) to orbit Earth -- have a special place in our memories of NASA. These animals paved the way for the United States space program by convincing biologists that animals' bodies *and* minds could function in orbit.
But there was a dark side to the missions. The chimps were the first to be trained by "avoidance conditioning" during which electric shocks were administered to the soles of their feet when the animals responded incorrectly in carrying out simple tasks. So, for example, the animals would be presented with three shapes and were trained to pick out the one that was not like the two others. They made their selections by pressing one of three levers that corresponded to the three symbols. On problem one below, the chimp should press the middle lever. On problem two, the chimp should press the right lever, and so on. Scientists call these oddity problems.
After Enos was in orbit, his first battery of oddity problems went as well as could be expected. After 18 problems, Enos had received 10 shocks. But on his next battery of tests, the center lever malfunctioned as did the switch controlling which question was presented. Enos kept being presented the same problem -- number one above -- in which the correct answer required pressing the center lever, but his center lever was broken. Enos, strapped into a space module orbiting the earth, was subjected to 33 shocks in a row, no matter what he did. The chimp kept trying to press different levers, NASA researchers record, but he kept getting shocked. Mercifully, the test ended after 35 shocks, and Enos performed normally on the other tasks he was given.