Scratch Monkey Story

11 February 1987

This morning, I spoke for an hour with Laura Creighton, who wrote the device driver for the equipment between the monkeys and the computer.

This incident happened at the University of Toronto in late November of 1979 or 1980. The zoology department had used digital-to-analog and analog-to-digital converters in a large number of experiments, including attempting to synthesize pheromones to reduce breeding of beetles that fed on tobacco crops, some rat neurological experiments, and some cricket behavior/population studies. The rat experiments involved implanting electrodes in the rats' brains, and the rats experienced some pain. The Humane Society learned of this and raised complaints, resulting in the shutting down of the zoology department for a day while the experiment was stopped. The University of Toronto has the third or fourth most respected zoology department in the world and wanted to maintain that prestige, so there was lots of screaming to avoid having such a thing happening again.

The various data from the experiments was collected by PDP-11/05 front ends and sent to an 11/44. Laura Creighton had written the software for this, fixing a problem they had previously with the 11/44 not being fast enough to collect the data by itself. This was being done for 16 to 18 experiments.

The folks in the physiology section of the Department of Medicine (separate from Science, which contained the zoology department) had bought their first VAX, an 11/780, and wanted a similar set-up. So Laura Creighton and the zoology department agreed to set up their software for this. The physiology people decided not to use 11/05s in between, since the VAX was fast enough to handle the data. So five monkeys were fitted with caps intended to sense brain waves, and the caps were attached to various A-to-D and D-to-A converters (which were US Army surplus from 1956) which were in turn connected to the VAX. This connection was piggybacked on a disk drive (pre-RL02), which contained a disk and was mounted read-only—the read-only button was pressed and taped over with a warning not to remove it. In normal operation, software would read data from that drive and write it to a regular disk. The room containing the monkeys was several stories removed from the computer room.

After some time, the VAX crashed. It was on a service contract, and Digital was called. Laura Creighton was not called although she was on the short list of people who were supposed to be called in case of problem. The Digital Field Service engineer came in, removed the disk from the drive, figured it was then okay to remove the tape and make the drive writeable, and proceeded to put a scratch disk into the drive and run diagnostics which wrote to that drive.

Well, diagnostics for disk drives are designed to shake up the equipment. But monkey brains are not designed to handle the electrical signals they received. You can imagine the convulsions that resulted. Two of the monkeys were stunned, and three died. The Digital engineer needed to be calmed down; he was going to call the Humane Society. This became known as the Great Dead Monkey Project, and it leads of course to the aphorism I use as my motto: You should not conduct tests while valuable monkeys are connected, so "Always mount a scratch monkey."

Laura Creighton points out that although this is told as a gruesomely amusing story, three monkeys did lose their lives, and there are lessons to be learned in treatment of animals and risk management. Particularly, the sign on the disk drive should have explained why the drive should never have been enabled for write access.


If you are interested in computer folklore, you might wish to read the story of Mel.