Do droids feel pain?

One of my favorite parts of my existence as a scientist is the wild range of questions people ask me. My favorites include “how do I know when I have to pee?” (asked by a ~2 year old, to his parents’ mortification) and “if zombies are a nervous system virus, then what are vampires?”

Today: do droids (or robots or replicants or andys or terminators, or whatever your particular franchise calls them) feel pain? Answer below the cut.

Short answer: if their designers have any sense, yes, droids should feel pain.

Long answer:

In order to answer whether droids feel pain, we must ask: what *is* pain?

only mostly dead

At its essence, pain is a signal to tell you that you should knock it off, whatever you’re doing, where to knock it off, and what is happening to your body as a consequence of you not knocking it off already and WHY haven’t you STOPPED?? These three components – (1) the damage signal, (2) the location, and (3) the unpleasantness or aversion – combine to form a signal that is meant to prevent damage to you.

Your body actually processes pain as multiple component signals that both combine and divide to generate these sensations.

Imagine a TERRIBLE pain: you have stepped on a lego. Your body sends a signal that communicates these three components:

1. Damage

The two-by-three block sinking into meaty sole of your foot deforms the skin and muscle. This is just one type of pain – thanks to the creativity of nature and its denizens, the sources of pain are infinite. The two types you have mostly experienced are pain receptors being activated (by mechanical damage such as a break or a cut, chemical spills, burns, or whatever else you’ve done to yourself this time) and inflammation (the body’s own response to damage). That’s right, there are cells in your body, from your skin to your joints to your guts, whose sole purpose is to make you feel pain. These cells, properly called nociceptors, can be activated by dangerously hot or cold temperatures, being physically pressed too hard or pulled out of shape, the presence of chemicals related to cell damage, or dangerous chemicals that might hurt you. The different causes of damage will trigger activity in different kinds of cells, telling you generally what’s wrong.

You might have also experienced neuropathy – nerves sending false signals of pain for no good reason. This can come from conditions like diabetes, many kinds of peripheral nerve damage, and lots of other conditions. Neuropathic pain is notoriously difficult to deal with because the pain receptors aren’t actually responding to any stimulus, so we have to address a misfiring nervous system directly.

2. Location

This one’s pretty obvious. You need to know where it hurts. Pain travels along similar but not identical routes as regular old touch, from the body to the spinal cord to the brain.

3. Aversion

And finally, the sensation that makes pain, well, painful. Aversion is the part of the signal that makes you pull your foot back and rip the embedded demon block out as fast as you can. Aversion is an affective signal, which means it makes you feel an emotion, and consequently an impulse to do something. Pain tells you that if whatever it is you’re doing is going to cause damage to your body, you should probably stop doing that thing, as quickly as you can, and you’re not going to be too happy until you do.

Of course, we’re perfectly capable of continuing to do whatever it is we’re doing even though it hurts, because we have no choice or because it’s that important. But overall, pain is good. On the flip side, a lack of pain is bad.

A very small number of people of people have a genetic condition called congenital insensitivity to pain. These people have defective pain receptors that don’t work, and therefore can’t feel any type of pain. They still feel sensations – but nothing distinguishes damaging sensations like a burn or a cut from any other type of experience. Interestingly, the condition also makes them unable to sweat, because their temperature receptors don’t work right either. You might think, that’s awesome, you’re never in pain! But these people often wind up with disfiguring or life-threatening injuries, because while they feel the location and some sensation, they never feel the aversion that makes them stop. One of the biggest diagnostic markers is that kids will often chew off part of their own tongues while teething, because it just doesn’t hurt and the sensation is interesting to them.

So. Pain is good.

Now, instead of stepping on a lego yourself, consider a droid stepping (or… rolling over?) a lego. And instead of a lego, it’s a nail – something that could really seriously damage it. Why should you, the brilliant and extravagantly-funded inventor of the perfect robot, introduce something so awful as pain to your highly intelligent robot capable of making its own decisions like a grown up? Because it’ll stop your robot from damaging itself into oblivion over and over until even your expansive funding runs out. (Also, like STEM fields ever have excess money. Please.)

If a robot does not feel pain, or something like it, they’ll likely end up like the people with congenital insensitivity to pain. They will do things that cause damage to their body, because there is no signal that distinguishes damage from any other sensation, and therefore they won’t know to stop before taking a critical hit. Your unit will continue doing exactly what it was doing, despite the giant nail sticking out of its treads or wrenched leg causing damage to a hip joint. Including a function that detects the type and location of damage, and kicks off some protocols to avert further damaging sensations, will help the robot function better, more safely, and for longer. Unless the robot also feels emotions, it won’t experience the affective part of pain the way we do. But to save your robot’s body, it still pays to have aversion built in.

Now that I’ve ruined your next viewing of Star Wars, what’s your next question?

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