How likely is it that cockroaches feel fear?

February 1, 2013 4:50 PM

From Googling it seems to be unknown as to whether or not cockroaches are exhibiting fear when confronted or some more basic instinct. Even if it's not 100% known, is there strong evidence either way?

I feel tremendous guilt after killing bugs. The idea that something could be afraid of me and then I kill it (justifying its fear) weighs heavily on me every time. I try to be as humane in my bug-proofing as I can but sometimes it's me or the roach (I am also pretty scared of them and find trying to catch one in a cup or something petrifying).

What I'm trying to figure out is if, when they freeze and seem to be staring at me, they are feeling something like what I am feeling: terror.

posted by Danila to pets & animals (17 answers total)

You'd better define 'fear' first. Some degree of predator avoidance or avoidance is pretty basic behavior in most living things that have mobility; it's what has kept their ancestors around long enough to procreate. That doesn't mean, however, that their buggy lives are flashing before their eyes, causing them to suddenly realize with a profound feeling of dread the finite nature of their own existence.

I suspect that 'terror' is sufficiently complex as to require at least a spinal cord (excepting octopi, of course).
posted by percor at 4:56 PM on February 1

Well, in that "terror" as I think of it in humans is itself a biological, pre-cortical reaction, it's conceivable that any creature with a bent for self-preservation can experience "terror." That said, cockroaches almost certainly don't experience anything we'd recognize as, well, experience.

Do roaches have a danger avoidance mechanism? Yes.
Do they get PTSD if they escape? No.
posted by cmoj at 5:16 PM on February 1

I don't know about fear but I have had large roaches charge me when I was trying to kill them. Just for the record, I work in an urban library with some vermin problems.

I think when they freeze they are trying not to be seen.
posted by amapolaroja at 5:17 PM on February 1

Do cockroaches experience fear before you kill them? No. It's probably more of a cross between despair and resignation.

But seriously, cockroaches brains have about 1/85000th as many neurons as ours. While they have some basic danger recognition and avoidance capabilities, your own experiences with fear are not really comparable to what they are subjectively feeling, if they even have subjective feelings.

Bottom line: bugs are not people and do not feel people feelings. Prescription: Watch fewer Pixar movies.
posted by aubilenon at 5:28 PM on February 1 [5 favorites]

How would you know? I don't mean this as a rhetorical question, I'm asking because it might help you define what you mean by fear if you think about it as a testable scientific question: literally how would you determine through experiments whether or not cockroaches feel fear?

For example I don't know about roach psychology, but I'm pretty sure based on observing my dog that he feels fear. I could imagine the types of experiments you could do on dogs to test this, for example brain imaging studies to see what parts of their brains are activated when they are in a potentially scary situation, or measurements of hormones like cortisol that are associated with stress/fear in humans, or characterizing a canine version of PTSD (this is apparently a thing).

Also, at the risk of adding more guilt it may help you to think through the fact that other creatures have to die for you to live. I'm a vegetarian because I think it's more ethical than killing animals but I still kill lots of plants in order to eat. Ethically I'm ok with that. Because roaches are gross and dirty, I think that not letting them infest my house is pretty important. Therefore although I don't like to kill bugs I'm ethically ok with killing roaches to keep them from living in my house.
posted by medusa at 5:37 PM on February 1 [1 favorite]

It's a tricky thing, to try to draw a line and say that everything above the line is "conscious" and everything below the line is not. How do you analyze another creature's experience of life? How do you place a value on that experience? To look at another life, however simple, and decide that it is within your purview to end it, strikes me as arrogant.

Personally, I draw that line as low down as possible. If something would rather I didn't kill it, by which I mean it displays even the most rudimentary danger-avoidance mechanisms, then I try not to.

I've been fortunate not to have to deal with serious bug infestations in my adult life. If I did, I'd probably come down in the same place as Medusa.

There are people out there who take this idea to its logical conclusion. I don't sweep my path or wear a mask like Jainist monastics. But I understand and respect why they do.

Let me put it this way: if we were visited by an advanced alien species, such that aliens:us::us:cockroaches, I'd hope they were more like the Jainists and less like the average homo sapiens.
posted by zjacreman at 6:00 PM on February 1

Just based on the quickness of their disappearing act I would guess that it is more of a basic instinct.

Not sure about how their eyesight works, but whenever I try to kill a cockroach I have to sneak up on it and suddenly smash something down on it...and even then sometimes it gets away, and then I am the one struck with fear, wondering where it is. So it seems like if it has time to see me coming/fear me, it will try to get away.
posted by fromageball at 6:01 PM on February 1

Fear as I experience it as a human has a thinking-component. It can leave me shaken even after the danger has passed. Do the roaches have this type of anxiety as well or do they freeze when the danger is there and move on with their lives when it is not? To me, that is the difference between fear as emotion and fear as basic protective instinct. Is any part of it shaken by the encounter?
posted by Danila at 6:03 PM on February 1

I'm sure they don't instantly drop out of fight-or-flight mode the second the danger goes away.

I am pretty sure they don't agonize about you two days later though.
posted by aubilenon at 6:36 PM on February 1

when they freeze and seem to be staring at me, they are feeling something like what I am feeling: terror.

The cockroaches aren't staring at you - they have compound eyes that are designed primarily to sense movement.

I guess some people are asking the question of whether or not insects have emotions:

On the one hand, invertebrates lack a cortex, amygdala, as well as many of the other major brain structures routinely implicated in human emotion... On the other hand, some invertebrates, including insects, do posses the rudiments of our stress response system.

In a procedure meant to simulate a badger attack on a hive, the bees were shaken for one minute in a benchtop machine used to vigorously mix chemicals. If anything would put bees in bad mood, this would be it.

Next, both shaken and unshaken bees were tested on five mixtures of hexanol and octanone at different concentrations. Unsurprisingly, both groups were more likely to advance their mouths to octanol heavy mixtures (which predicted sugar) than hexanol heavy mixtures (which predicted quinine). Interestingly though, the shaken bees were more reluctant to advance toward the mixtures than their unshaken counterparts
posted by KokuRyu at 7:34 PM on February 1 [2 favorites]

So maybe cockroaches do experience something akin to a negative feeling when you stalk them. They're probably terrified.

If this makes you hesitate about killing them, consider this:

Cockroaches communicate by shitting all over the place - on your floor, on the counter, in the linen closet, under your bed, everywhere. And cockroach feces can trigger asthma, not to mention other diseases.

I'm not sure if the cockroaches lie awake at night stressed about the fact that they crapped on your toothbrush or are making it difficult for you to breath.

However, a friend of mine who lives in the country suddenly gave up competitive games like chess when he turned 60. He also stopped killing things like cockroaches. He just lets them back outside, where they came from (he's lucky - he doesn't live in an urban environment where cockroaches are a major pest).

So there are other people who feel as you do too.
posted by KokuRyu at 7:39 PM on February 1 [1 favorite]

IANA entomologist, although I used to work with live insects at a science museum -- not roaches, though, so extrapolate from this what you will. Going to skip over the little I know about insect nervous systems, and answer as a fellow human being who hates to cause unnecessary suffering to most any ole critter.

Insects do not experience terror, as you define it. And they do not ruminate. I think of them as experiencing two "emotions" - "Yes" and "No". A tasty banana - Yes! A person's jabbing finger - No! (And maybe a third -- "What the Hell is That?") But while they certainly react strongly enough to stimuli that brought about the Yes and the No, they do not seem to retain the Yes-ness or No-ness into their next interaction. They move on well.

Example: A butterfly would fall into the exhibit pond, and I would carefully dry it off -- after which it would go about its life as if nothing had ever happened! As if it hadn't nearly drowned, or been picked up by a scary giant, or hadn't narrowly escaped being eaten by a swarm of fish. It didn't remember. Or if it did, it wasn't important anymore.

And if a butterfly had permanently lost its ability to fly, we would just park it on top of a piece of fruit. Its little proboscis would roll out, and feeding would commence. For a while, it would completely forget that it couldn't fly. That's like a person forgetting they can no longer walk or speak, just because someone gave them a really good candy bar.

That's not to say that there is no value in being sympathetic or merciful toward insects. I certainly am, and mercy is a lovely quality to cultivate. But when you have to kill or relocate a roach, you don't have to worry that you are striking pure terror into their hearts. If they survive their encounter with you, they'll forget you soon. If they don't, they didn't spend their last moments filled with dread. They would just be reacting instinctively.
posted by Coatlicue at 9:16 PM on February 1 [11 favorites]

I can't seem to find the paper he references here, but here's a brief excerpt from Being There by Andy Clark that I think you might find interesting:

"Take, for example, the humble cockroach. The roach is heir to a considerable body of cockroach-style commonsense knowledge. At least, that is how it must appear to any theorist who thinks explicit knowledge is the key to sensible-looking real world behavior! For the roach is a formidable escape artist, capable of taking evasive action that is shaped by a multitude of internal and external factors. Here is a brief list, abstracted from Ritzmann's (1993) detailed study, of the escape skills of the American Cockroach, Periplaneta americana:

The roach senses the wind disturbance caused by the motion of an attacking predator.
It distinguishes winds caused by predators from normal breezes and air currents.
It does not avoid contact with other roaches.
When it does initiate an escape motion, it does not simply run at random. Instead, it takes into account its own initial orientation, the presence of obstacles (such as walls and corners), the degree of illumination, and the direction of the wind.

No wonder they always get away! This last nexus of contextual considerations, as Ritzmann points out, leads to a response that is much more intelligent than the simple "sense predator and initiate random run" reflex that cockroach experts (for such that there be) once imagined was the whole story.
...
How does the roach manage its escapes? The neural mechanisms are now beginning to be understood. Wind fronts are detected by two cerci. (antenna-like structures located at the rear of the abdomen). Each cercus is covered with hairs sensitive to wind velocity and direction. Escape motions are activated only if the wind is accelerating at 0.6 m/s^2 or more: this is how the creature discriminated ordinary breezes from the lunges of attackers. The interval between sensing and response is very short: 58 milliseconds for a stationary roach and 14 milliseconds for a walking roach. The initial response is a turn that takes between 20 and 30 milliseconds (Ritzmann 1993, pp. 113-116)."

I never realized how much depth those little guys have, but the point I'm getting at is that, at least from the way the escape reflex is described here, it doesn't seem as if the roach is experiencing fear as we know it.
posted by Gymnopedist at 9:44 PM on February 1 [4 favorites]

If something would rather I didn't kill it, by which I mean it displays even the most rudimentary danger-avoidance mechanisms, then I try not to.

Even bacteria pass this test.
posted by lambdaphage at 10:57 PM on February 1 [2 favorites]

Whenever this question comes up, I prefer to reverse the framing such that it isn't a question of animals feeling human emotions, but humans experiencing animal stimulus and response systems. Heck, science has shown it even applies to love.

Because we're conscious we attribute emotional framing to these reactions, but it's basically a philosophical unanswerable as to which is the more "real" way to experience things.

So, no -- I don't think the cockroaches experience fear. I can tell you that cockroaches are way below mice in my priority system, and I don't feel any guilt for trapping/drowning mice (something I have to deal with frequently as a landlord). Recently I had a mouse on a glue trap -- actually he had scooted the one glue trap over to the other one and had gotten partially stuck on both -- that I had to put out of his misery. I felt a little bit of guilt there, but I still had to do it, because it was him or me in a broad sense, a natural conflict that wasn't either of our faults. If I were to live in a way that I had no conflicts with other living creatures whatsoever, I would find it very difficult to live anything close to a normal life.
posted by dhartung at 12:24 AM on February 2

I remember hearing somewhere years ago that roaches dream. I don't like the idea of killing something that can dream, but I can't find any reference to this online and I wonder how you'd even study it to find out. Do they make tiny, tiny electrodes to measure roach REM?

Dhartung, I'm no mouse expert, but it seems like there must be ways to catch mice and release them, without killing them. I read about an experiment recently where mice appeared to show empathy, they wouldn't shock their fellow mice even if they earned themselves a treat. Pet mice can definitely recognize their owners and show affection. I understand that mice can be pests and they can cause real problems, but if there's a way to get rid of them without killing them, I hope you'll try it.
posted by Ursula Hitler at 2:40 AM on February 2

Fear is a psychological phenomenon requiring consciousness. Cockroaches don't have the neural equipment required to experience fear.
posted by slkinsey at 7:37 AM on February 2