-------- Forwarded Message --------
whyevolutionistrue posted: "The Oxford English Dictionary gives
three relevant definitions of the adjective "sentient": a.) That
feels or is capable of feeling; having the power or function of
sensation or of perception by the senses. b.) Conscious or
percipient of something. " Why Evolution Is True [4]
ARE INSECTS SENTIENT? [5]
whyevolutionistrue
Jun 25
The _Oxford English Dictionary_ gives three relevant definitions of
the adjective "sentient":
a.) That feels or is capable of feeling; having the power or
function of sensation or of perception by the senses.
b.) Conscious or percipient _of_ something.
c.) _Physiology_. Of organs or tissues: Responsive to sensory
stimuli.
("Sentience" itself is defined only as "The condition or quality of
being sentient, consciousness, susceptibility to sensation.")
The question that the _Scientific American_ article below asks (and
for once it's written by a scientist in this field [6]) is whether
insects fit the definition of the first two definitions: do they
have feelings and sensations experiencing _qualia [7]_ like pain,
joy, pleasure, or the sensation of "redness"? Or are insects merely
chitinous robots that are _programmed by evolution to act (to us) as
if they have feelings—_programmed reactions that we
anthropormophize as similar to our own sensations? After all, you
can be "responsive to sensory stimuli" (the third sense above)
without actually _feeling_ the sensory stimuli the way humans do.
Answering the question of whether a bee or a fly is sentient in the
first two senses, or has consciousness (the ability to be sentient
and perceive stimuli), is difficult. Some would say it's impossible.
After all, we all know that we ourselves have consciousness and
feel pain and joy, because we experience those things personally.
But can I _prove_ that, say, another person is conscious? Not
directly, because we can't get inside their brains. We _infer_ that
they're conscious because they tell us they are; they are physically
constructed with the same neurons that give _us_ consciousness; and
they act as if they experience qualia. It's inference, but of a
Bayesian sort, and the question has high priors.
But can we extend this to other species? Chittka uses the example
of dogs:
Although there is still no universally accepted, single
experimental proof for pain experiences in any animal, common
sense dictates that as we accumulate ever more pieces of evidence
that insects can feel, the probability that they are indeed
sentient increases. For example, if a dog with an injured paw
whimpers, licks the wound, limps, lowers pressure on the paw while
walking, learns to avoid the place where the injury happened and
seeks out analgesics when offered, we have reasonable grounds to
assume that the dog is indeed experiencing something unpleasant.
This is a Bayesian approach to the question, and it's really the
only way to go. Yes, I think it's highly probable that dogs, and
most mammals, feel pain. But what about insects, reptiles and
amphibians? They certainly avoid unpleasant stimuli and gravitate
towards them, which you could interpret as feeling joy, pleasure, or
pain, but do they _feel_ these sensations? If you say that the
behavior denotes sentience, well remember that protozoans do these
things too (see below).
I'm fully aware that philosophers of mind have probably discussed
this issue at length, and I haven't followed that literature, so my
musings her may seem childish to these philosophers. But this _Sci.
Am_. article (click below to read, or find it archived here) [8]is
not written for philosophesr of mind but for people like me: folks
interested in science and wanting to see what's happening in other
fields. I found the article quite interesting, and for me it
_slightly_ raised the probability that insects can feel pain, but
the question remains far from settled—or even having a high
probability. And the author admits that. But he cites a number of
cool studies.
[9]
Here are the lines of evidence that, to Chittka, raise the Bayesian
probability that insects have sentience: experiencing pain,
pleasure, and even joy.
A.) THEY LEARN AND CAN DO REALLY SMART THINGS. (All quotes from
Chittka are indented):
The conventional wisdom about insects has been that they are
automatons—unthinking, unfeeling creatures whose behavior is
entirely hardwired. But in the 1990s researchers began making
startling discoveries about insect minds. It's not just the bees.
Some species of wasps recognize their nest mates' faces and
acquire impressive social skills. For example, they can infer the
fighting strengths of other wasps relative to their own just by
watching other wasps fight among themselves. Ants rescue nest
mates buried under rubble, digging away only over trapped (and
thus invisible) body parts, inferring the body dimension from
those parts that are visible above the surface. Flies immersed in
virtual reality display attention and awareness of the passing of
time. Locusts can visually estimate rung distances when walking on
a ladder and then plan their step width accordingly (even when the
target is hidden from sight after the movement is initiated).
All of these responses, of course, could come from computers
programmed to learn form experience, which is exactly what we and
other animals are. Natural selection has endowed us with a neuronal
network that will make us behave in ways to further our reproduction
(or, sometimes, that of our group—like an ant colony). We can
program computers to do this, too: robots that avoid aversive
stimuli and gravitate towards good ones. And clearly we behave in
such a way that furthers our reproduction, of which survival is one
component. But do insects experience the world, with its pleasures
and pains, by having qualia similar to ours?
A related question is this: is consciousness like we have (feeling
pain and joy) something that's merely an epiphenomenon of having
evolved a sufficiently complex nervous system, or is consciousness
itself a product of natural selection to further our reproduction?
We don't know the answer, but it's pretty clear that some of our
conscious experiences, like pain, have evolved by selection. People
who can't feel pain as a result of neurological conditions or
disease (like Hansen's disease), quickly start getting infections,
hurting their bodies without being aware, losing fingers, and the
like. If you didn't experience pain when putting your hand in
boiling water, you'd damage your body. If consciousness is just an
epiphenomen of a complex evolved nervous system, then we can't
automatically say that bees that act as if they're conscious are
_really_ conscious.
I'm prepared to believe, based on what I said above, that mammals
feel pain. Maybe even reptiles or amphibians, though there are
suggestions that fish don't feel pain, [10] at least in the way we
do. All these creatures gravitate towards adaptive things and avoid
nonadaptive ones, but again, they could be programmed to do so
without the ancillary conscious experience that we have.
More evidence from Chittka:
B.) INSECTS ACT AS IF THEY CAN ALTER THEIR CONSCIOUSNESS:
Many plants contain bitter substances such as nicotine and
caffeine to deter herbivores, but these substances are also found
in low concentrations in some floral nectars. Researchers wondered
whether pollinators might be deterred by such nectars, but they
discovered the opposite. Bees actively seek out drugs [1] such as
nicotine and caffeine when given the choice and even self-medicate
with nicotine when sick. Male fruit flies stressed by being
deprived of mating opportunities prefer food containing alcohol
(naturally present in fermenting fruit), and bees even show
withdrawal symptoms when weaned off an alcohol-rich diet.
Again, seeking out things that are good for you, like curing you of
illness or infection, could be programmed, either directly or as
part of programs involved in "learning what gets rid of harmful
conditions". Now if bees are partial coffee and cigarettes because
it gets them high, then yes, it seems to show that they want to
alter their consciousness, which implies that they _have_
consciousness. But these facts aren't that convincing to me, because
nicotine and caffeine may have other beneficial physiological
effects.
C.) BEES APPEAR TO BE "OPTIMISTIC". Here's the experiment Chittka
adduces to support that:
We trained one group of bees to associate the color blue with a
sugary reward and green with no reward, and another group of bees
to make the opposite association. We then presented the bees with
a turquoise color, a shade intermediate between blue and green. A
lucky subset of bees received a surprise sugar treat right before
seeing the turquoise color; the other bees did not. The bees'
response to the ambiguous stimulus depended on whether they
received a treat before the test: those that got the pretest sugar
approached the intermediate color faster than those that didn't.
The results indicate that when the bees were surprised with a
reward, they experienced an optimistic state of mind. This state,
which was found to be related to the neurotransmitter dopamine,
made the bees more upbeat, if you will, about ambiguous
stimuli—they approached it as they would the blue or green
colors they were trained to associate with a reward.
This is not a meaningless experiment, but to me shows only that bees
conditioned to approach a color after a sugar reward are more likely
to approach _something like that color_ than those who weren't
conditioned. To call this "optimism" seems to me hyperbolically
anthropomorphic.
D). BEES APPEAR TO EXPERIENCE "JOY". This experiment is more
suggestive to me:
Other work suggests that bees can experience not only optimism but
also joy. Some years ago we trained bumblebees to roll tiny balls
to a goal area to obtain a nectar reward—a form of object
manipulation equivalent to human usage of a coin in a vending
machine. In the course of these experiments, we noticed that some
bees rolled the balls around even when no sugar reward was being
offered. We suspected that this might be a form of play behavior.
Recently we confirmed this hunch [2] experimentally. We connected
a bumblebee colony to an arena equipped with mobile balls on one
side, immobile balls on the other, and an unobstructed path
through the middle that led to a feeding station containing freely
available sugar solution and pollen. Bees went out of their way to
return again and again to a “play area” where they rolled the
mobile balls in all directions and often for extended periods
without a sugar reward, even though plenty of food was provided
nearby. There seemed to be something inherently enjoyable [3] in
the activity itself. In line with what other researchers have
observed in vertebrate creatures at play, young bees engaged more
often with the balls than older ones. And males played more than
females (male bumblebees don't work for the colony and therefore
have a lot more time on their hands). These experiments are not
merely cute—they provide further evidence of positive
emotionlike states in bees.
It's hard to understand these results without thinking that bees,
like panda cubs, are playful, messing around with balls that give
them pleasure. And since bees don't experience balls in their
natural state, they could be enjoying the novelty. On the other
hand, they could simply be encountering something they haven't
experienced, and are following neuronal instructions to manipulate
it to see how it operates, which could be useful knowledge in the
future. This second interpretation means that no "pleasure" need be
involved. Remember, play behavior in animals is often there to
prepare them for what happens when their adults, and isn't just
there for pleasure.
Again, it's hard to judge from such studies whether bees are feeling
pleasure in the way we do. But to me this makes it marginally more
likely.
Finally,
E). BEES APPEAR TO WEIGH PAIN AGAINST PLEASURE, AND CHANGE THEIR
BEHAVIORS WHEN THE BALANCE IS ALTERED. Here's another experiment:
We decided to do an experiment with only moderately unpleasant
stimuli, not injurious ones—and one in which bees could freely
choose whether to experience these stimuli.
We gave bees a choice between two types of artificial flowers.
Some were heated to 55 degrees Celsius (lower than your cup of
coffee but still hot), and others were not. We varied the rewards
given for visiting the flowers. Bees clearly avoided the heat when
rewards for both flower types were equal. On its own, such a
reaction could be interpreted as resulting from a simple reflex,
without an “ouch-like” experience. But a hallmark of pain in
humans is that it is not just an automatic, reflexlike response.
Instead one may opt to grit one's teeth and bear the
discomfort—for example, if a reward is at stake. It turns out
that bees have just this kind of flexibility. When the rewards at
the heated flowers were high, the bees chose to land on them.
Apparently it was worth their while to endure the discomfort. They
did not have to rely on concurrent stimuli to make this trade-off.
Even when heat and reward were removed from the flowers, bees
judged the advantages and disadvantages of each flower type from
memory and were thus able to make comparisons of the options in
their minds.
To me, this really shows nothing more than animals are attracted to
adaptive stimuli and repelled by harmful ones, with the addition of
being able to balance harms versus advantages. (This is like the
"flight distance" of animals, with some individuals able to give
more weight to attractive stimuli. That's probably how cats got
domesticated!) But it doesn't tell us whether animals are _feeling
the pain or attraction the way we do._
And we should remember that even protozoans show avoidance of some
external stimuli [11] and can be induced by electrical shocks to
avoid light. [12]So these animals can be trained. Do they feel pain
or pleasure? I doubt it—not protozoa! They may not show "play"
behavior, but perhaps they can be trained to weigh aversive versus
adaptive stimuli, as in section "d" above. I doubt anybody would
conclude with confidence that protozoa feel pain the way we do (they
don't have a nervous system) or are even conscious.
Against the doubts that I've raised, Chittka offers a
counterargument:
Critics could argue that each of the behaviors described earlier
could also be programmed into a nonconscious robot. But nature
cannot afford to generate beings that just pretend to be sentient.
Although there is still no universally accepted, single
experimental proof for pain experiences in any animal, common
sense dictates that as we accumulate ever more pieces of evidence
that insects can feel, the probability that they are indeed
sentient increases.
The first sentence is what I have said already. And I'm willing to
go along with the third sentence, too: as we learn more, the
Bayesian probability that other species experience pain or pleasure
can increase or decrease.
But I'm not willing to go along with the idea that "nature cannot
afford to generate beings that just pretend to be sentient." What
does he mean by "afford"? My interpretation is this: he's saying
that natural selection cannot produce organisms that act as if
they're sentient _unless they really are sentient_. And I cannot see
any support for that, for we already know that protozoans act as if
they experience qualia, but almost certainly don't. And saying
"pretend to be sentient" is pretty anthropormorphic! It implies, for
example, that programmed robots that do what bees do are "pretending
to be sentient" when in fact we _know_ they are NOT sentient.
Finally, that leads to the Big AI Question: if we generate robots
sufficiently complex that they respond exactly as humans do in
complex situations requiring consciousness, does that mean that they
have _become_ conscious? I say "no", but others disagree. After
all, there are those panpsychists who say that even electrons and
rocks have a rudimentary form of consciousness.
I'm writing this on the fly, so forgive me if my thoughts are
half-baked. I do think that Chtittka's experiments are clever, and,
over time, may give us a sense of sentience in other species. But
I'm not yet ready to throw in with him on the claim that insects are
conscious. It's enough for me now to realize that they do
experience some aspects of the environment as things to be avoided.
And that is why I have always anesthetized my fruit flies before
killing them. (When I was an undergrad I used to take them to the
biology department roof and let them go, but my advisor Bruce Grant
nixed that on the grounds that I was polluting the natural gene pool
of _Drosophila_.)
The last bit of Chittka's paper is a thoughtful analysis of how
these kinds of studies should condition our behavior towards
insects. But even if they don't feel pain, aversion or attraction
itself should help us confect a philosophy of "insect ethics."
h/t: Howard, who brought this paper to my attention and wanted my
take on it. I'm sending him this link as my take.
Comment [13]
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