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The first American to operate spacecraft controls (instead of being a passive passenger) was Ham the chimpanzee. He was trained to push some levers, which he did about 50 times during his flight.

Was he following commands from someone on the ground? Repeating a sequence given to him during training? Randomly choose which levers to push? Or something else?

Ham in his capsule, with levers

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    $\begingroup$ Obligatory: i.imgur.com/ZsLkPpV.jpg $\endgroup$ – Organic Marble May 6 at 23:10
  • $\begingroup$ The chapter in "The Right Stuff" about this flight is absolutely great. $\endgroup$ – Organic Marble May 6 at 23:15
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    $\begingroup$ But he did not operate any spacecraft controls. He did operate controls in a spacecraft, but these controls did not influence the spacecraft at all. He did not change the spacecrafts attitude or speed. $\endgroup$ – Uwe May 7 at 19:41
  • $\begingroup$ @Uwe: I did struggle with how to word that, as I was trying to be concise, but not imply that he was controlling the spacecraft. I also considered "first American astronaut", but he had neither finished an astronaut training program, nor was he the first American being above the Karman line. $\endgroup$ – DrSheldon May 7 at 21:42
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I'll preface my answer with the comment that it was a different time and the way that experimental animals, even primates, were treated was different than today.

tl;dr the chimpanzee was trained to press levers upon the illumination of light signals to avoid receiving electrical shocks.

Details follow:

Subject 61 (aka Ham for Holloman Aerospace Medicine) got 29 training sessions prior to launch. The spacecraft console looked like this:

enter image description here

Plates were strapped to the chimpanzee's feet that delivered a "mild electrical shock".

The ballistic unit presented two shock-avoidance programs. The primate had to depress levers in response to colored light stimuli within a certain time period to avoid a mild shock.

..............

Each response by the subject on the right-hand lever postponed the occurrence of the next scheduled shock for 15 seconds and, as a consequence, a consistent and stable rate of responding was developed by which the animal could avoid shocks indefinitely.

In contrast to the continuous task, discrete avoidance employed a signal as a warning of impending shock if the correct response was not made. In the MR-2 flight, the warning signal was the illumination of the blue light. This light came on once every 2 minutes. However, a fixed time interval was not employed during training in order to eliminate the possibility of temporal conditioning. The time between the appearance of the blue light and the pressing of the left lever was the subject's reaction time. During the flight the subject had to press the right lever at least once every 15 seconds and at the same time press the left lever within 5 seconds after each presentation of the blue light.

Results:

The excellent performance of the chimpanzee on the two required tasks was gratifying. Of the two shocks received during the flight, only one was deserved.

The undeserved shock (bad form, experimenters!) was explained thusly:

...it is believed that this shock was due to a malfunction in the timing apparatus since careful examination of the telemetry recording shows that the time between responses at this period of the flight was less than 15 seconds.

The orbital space chimp, Enos, had a more complicated console that could dispense banana flavored pellets and water (reward) as well as shocking him (punishment). That's all covered in the source document as well.

Source: Results of the Project Mercury Ballistic and Orbital Chimpanzee Flights

Bonus fact: This mission had an in-flight abort! Ham's escape tower fired, subjecting him to 17 g's.

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    $\begingroup$ did he manage to keep pulling his lever during the abort? $\endgroup$ – JCRM May 7 at 3:43
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    $\begingroup$ @JCRM page 11 says the tower fired at 2:18. The history of lever pulls chart shows a drop in the number of pulls between 120 and 140 seconds and the subject received a shock then (p. 24). See the plots on p.23 also. $\endgroup$ – Organic Marble May 7 at 4:36
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    $\begingroup$ @uhoh and the beginning of the 1980s movie "Ghostbusters" $\endgroup$ – Organic Marble May 7 at 12:47
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    $\begingroup$ Bill Murray is running an experiment, he shocks the male subject even on right answers and the female subject never. $\endgroup$ – Organic Marble May 7 at 12:50
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    $\begingroup$ The fact that most of the public news about this said only that he was "trained to press" levers, and left off the bit about the shocks, suggests an awareness that even then, there would have been less than full acceptance of it. $\endgroup$ – CCTO May 7 at 19:43

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