from AEON Website
(Apis mellifera) in the hive,
Photo by Mark Moffatt/Minden
with no inner life?
Close attention to
their behaviors and moods
Yet, for the most part, Descartes did not think very highly of the inner life of nonhuman animals.
Followers of Descartes have argued that consciousness is a 'uniquely' human attribute, perhaps facilitated by language, that allows us to communicate and coordinate our memories, sensations and plans over time.
On this view, versions of
which persist in some quarters today, nonhuman animals are little
more than clever automata with a toolkit of preprogrammed behaviors
that respond to specific triggers.
Scientists have long known that these creatures must possess a large behavioral repertoire in order to construct their elaborate homes, defend against intruders, and provision their young with food.
Yet many still find it plausible to look at bees and ants as little more than 'reflex machines', lacking an internal representation of the world, or an ability to foresee even the immediate future.
In the absence of external stimuli or internal triggers such as hunger, it's believed that the insect's mind is dark and its brain is switched off.
Insects are close to 'philosophical zombies':
But perhaps the problem is not that insects lack an inner life, but that they don't have a way to communicate it in terms we can understand.
It is hard for us to
prise open a window into their minds. So maybe we misdiagnose animal
brains as having machine-like properties simply because we
understand how machines work - whereas, to date, we have only a
fragmentary and imperfect insight into how even the simplest brains
process, store and retrieve information.
Not all of these lines of
evidence are from experiments specifically designed to explore
consciousness; in fact, some have lain buried in the literature for
decades, even centuries, without anyone recognizing their hidden
...now suggest that consciousness-like phenomena might not have evolved late in our history, as we previously thought.
Rather, they could be
evolutionarily ancient and have arisen in the Cambrian era, around
500 million years ago.
In an ever-changing and only semi-predictable environment, consciousness can solve this problem more efficiently than unconscious mechanisms possibly could.
It involves manifold features, but some include:
As the American zoologist Donald Griffin wrote in Animal Minds (1992):
Take honeybees, who have a symbolic 'language' by which they can communicate about the precise coordinates of food sources in flowers.
In this 'dance language', a successful scout bee returning from a good flower patch performs a repetitive sequence of movements in the dark hive on the vertical comb. These movements are keenly attended by other bees.
The successful forager moves forward in a straight line for a few centimeters.
Then she moves in a half circle to the left, back to her starting point, performs another straight run along the path of her first, and then circles to the right. The duration of the straight run tells other bees the distance to the food source (roughly one second of walking distance in the dance corresponds to a one-kilometer flight to the target).
The direction of this run
relative to gravity encodes the direction relative to the Sun - for
example, if the run in the hive is straight up, this tells other
bees to fly in the direction of the Sun (whereas 'down' means 'fly
in the opposite direction of the Sun').
A decade later, however, one of von Frisch's students, Martin Lindauer, peered into a beehive during the night and discovered that some bees advertised the locations of various foraging bonanzas they'd discovered the previous day.
Before midnight, they
'talked about' locations visited the previous evening - and in the
hours before sunrise, they discussed the locations they'd visited on
the morning prior.
The function is unclear. They might have 'just thought' about these locations spontaneously during the night. Or perhaps the communication is a strategy for consolidating their spatial memory.
Scientists have since found that a bee's memories of the previous day are strengthened when they are exposed to elements of these memories while in deep sleep.
Perhaps bees not only
think and 'talk', but dream...?
That's not what should happen if bees' memories are merely prompted by environmental stimuli, combined with internal triggers such as hunger.
Bees, then, appear to have at least one of the principal hallmarks of consciousness:
Deprived of its ability
to anticipate what it should see
as a result of its own intentions,
the fly behaved erratically...
The ability to recognize oneself is the origin of being able to distinguish one's self from another entity, as well as to plan, pay attention, recall memories of specific events, and take the perspective of another creature.
Many animals, such as
apes and corvids, display these abilities.
If the image on your retina suddenly tilts by 45 degrees, you know that this is fine, as long as it's the result of you deliberately inclining your head.
But if you didn't move
your head, you might be in the middle of an earthquake, and had
Under normal conditions, animals expect the environment to move in a predictable manner when they turn their heads voluntarily.
This allows them to
anticipate what will happen next, as a result of their own actions
In one of their experiments in 1950, they inverted the input to the fly's brain from the left and right eyes using a rather crude (and cruel) technique:
The result was that, when the animal turned left or right, the sensory signals were the opposite of those it expected. (They were not upside down since the experimental environment consisted of vertical stripes - so nothing changed in this regard.)
Deprived of its ability to anticipate what it should see as a result of its own intentions, the fly behaved completely erratically.
The authors concluded:
Insects, with their head in the normal position, appear to have another of the key ingredients of consciousness:
There is also evidence that insects have more than just a simple, internalized 'instruction book'.
Experimenters have tested this hypothesis by confronting insects with tasks that none of their evolutionary ancestors could have possibly encountered.
More than 200 years ago,
the blind Swiss naturalist François Huber (working with his
wife Marie-Aimée Lullin and servant François Burnens) suggested that
honeybees might display foresight in the construction of their
The honeybees took corrective action long before they had reached the glass:
Apparently, the bees had
extrapolated from their current location to the target zone, and
tried to avoid a suboptimal result.
However, on this occasion, not only did bees become active to fortify the dislodged comb with a number of pillars and crossbeams made from wax, they also reinforced the attachment zones of all the other combs on the glass ceiling - apparently to ensure that a similar disaster wouldn't happen again.
Such foresight, should it
be confirmed experimentally with modern methods and sample sizes, is
one of the hallmarks of consciousness. Notably, in this case, it
appears to extend well beyond just the immediate future.
The bees used social learning to solve the task by watching skilled demonstrator bees:
When later tested on their own, the observer bees did not choose the furthest ball from the centre, but its closest one.
They did this even when the closest ball was colored black instead of the yellow they'd been trained on. Importantly, observers had no prior experience with rolling the balls themselves (that is, no opportunity for trial-and-error learning).
These results indicated
that instead of simply 'aping' a learned technique, bumblebees
spontaneously improved on the strategy used by their instructor -
suggesting that they had an appreciation of the outcome of their
actions ('ball in goal').
They can certainly learn to associate visual patterns (such as those presented on flowers) with nectar rewards; but this doesn't necessarily imply that they have a little image of flowers floating around in their head.
A 2017 study (Insect Bio-inspired Neural Network Provides New Evidence on How...) looked at artificial neural networks, modeled on bees' brains, which deployed two simple feature detectors:
These algorithms were capable of recognizing complex visual patterns, like a circle carved into four, with stripes running at different angles in each quadrant.
So a bee could store
these complex visual patterns just by memorizing the signals from
these neurons - without actually storing full images in its memory.
that bees prefer flowers
whose nectar is laced
low levels of nicotine.
In this experiment, bees were first trained to distinguish two types of artificial flowers that were visually identical, but which had 'invisible patterns' made up of small scented holes that were either arranged in a circle or in a cross.
The bees were able to figure out these patterns by using their feelers.
The most exciting finding was that, if these patterns were suddenly made visible by the experimenter (so that the flowers now displayed visual circles or crosses), bees instantly recognized the image that was formerly just an ephemeral smell-pattern in the air.
This indicates that the
bees might indeed have a mental representation of the shape, rather
than recognizing patterns based on simple feature-detectors in their
They were then faced with an intermediate stimulus (in this case, turquoise). Intriguingly, they responded to this ambiguous stimulus in a 'glass half full', optimistic manner, if they had encountered a surprise reward (a tiny droplet of sucrose solution) on the way to the experiment.
But if they had to suffer
through an unexpected, adverse stimulus, they responded in a 'glass
half empty' (pessimistic) manner.
Psychotropic drugs are not just the province of humans; insects can be subject to their effects as well. Volatile anesthetics, appetite-suppressing stimulants, depressants and hallucinogens are naturally produced by various plants and fungi.
These are not only accidental byproducts of their biomolecular machinery, but for their own defence in deterring herbivores.
Yet they don't always deter:
The molecular biologist Galit Shohat-Ophir at Bar Ilan University in Israel and her colleagues discovered that fruit flies stressed by being deprived of mating opportunities reportedly seek out alcohol, which is widely present in nature in the form of fermented fruits.
This suggests that intentional 'sensation adjustment', or even 'mood adjustment', is widespread across the animal kingdom - which strongly suggests that animals have inner experiences.
It will be important to rule out alternative explanations, in which behavior is modified via direct effects on neurotransmission or the digestive system. But insect psychotropics should nonetheless be a promising avenue for future research.
After all, why would an
organism seek out mind-altering substances when there
isn't a mind to alter?
So humans can't make arguments on the basis that insects don't have human-type NCC. What we can say is that insect nervous systems are anything but simple.
While a bee brain has only about 1 million nerve cells, compared with around 85 billion in a human brain, some individual neurons have a complexity of branching that rivals a fully grown oak tree. A bee brain could have a billion synapses (the connections between neurons that can be shaped by experience).
In terms of the diversity of building blocks of the nervous system, even the humble fruit fly has more than 150 neuron types just in its visual system.
By comparison, the human retina has fewer than 100.
In addition to their intricacy, insect brains also have other physiological properties required for consciousness.
In a reflex machine, the
flow of information would be expected to go from the sense organs to
the mechanisms responsible for motor control. But in insects, there
are many top-down processes at work, in which neural cables send
messages from the central brain to the sensory periphery.
Attention allows animals to focus specifically on important stimuli (such as a familiar flower, if you're a bee) and disregard others (such as unfamiliar flowers).
The neuroscientist Bruno van Swinderen at the University of Queensland tested this by placing bees in a virtual reality environment that they could manipulate, and then measured their brain activity.
His team found neural activity patterns that corresponded to paying attention to one or another object, and also found certain brain states that preceded the bees' selection of one or another stimulus.
generated from 'within the brain' - that is, in the absence of or
distinct from external stimulation - is of particular interest in
the context of consciousness.
the 'central complex' of the insect brain
and the 'basal ganglia' of vertebrates
Like humans, where
different neural oscillations accompany deep sleep and REM sleep,
flies also have different patterns in different sleep phases. The
insect brain is never 'switched off' - as in bees, it seems that
flies also have dream-like states.
Rather than seeing these as instances of 'convergent evolution', where features pop up separately, Held and others have found evidence of certain shared underlying genetic scaffolds that produce these features in their various forms.
For example, we did not inherit our legs and eyes from insects, or by different modifications from a common ancestor.
The common ancestor of
humans and flies was an unknown legless worm of the Cambrian period.
Yet both humans and flies possess a head, a thorax, an abdomen,
legs, and sensory organs.
The anatomical and functional parallels between the 'central complex' of the insect brain and the 'basal ganglia' of vertebrates are striking, and point to a common origin. Defects in both these systems produce motor problems, impaired memory, attention deficits, emotional disorders and sleep disturbance.
According to Barron and
Klein, the central complex could be a likely contender for mediating
subjective experience in insects.
Planaria (flatworms), which do have a central nervous system, must have some form of consciousness, Darwin speculated.
In The Power of
Movement in Plants (1880), he went on to compare the animal
brain and the plant's 'root radicle' or
taproot. This taproot must
find its way, by some form of sampling and evaluation, to the best
sources of anchorage and nourishment.
While parts of plants might move, and stems can twine or lean, plants do not move their bodies as a whole.
They are able to
accomplish most of their tasks without needing to navigate in space,
which we think is critical for the first stages of development of a
distinction between self and world.
Our actions in the world rely to a surprising extent on stimuli we haven't consciously noticed.
Moreover, the experience of 'volition' has been found to follow our actions after a time-lag, rather than preceding them or being simultaneous with them. Some have interpreted this to mean that consciousness has no effect on behavior and is purely 'epiphenomenal'.
Instead, maybe the brain collects and weighs current environmental stimuli and data from memory, computes the best behavioral option, and makes the choice for us by initiating an action.
If consciousness is
causally ineffective, the argument that animals need it for living
is unavailable. Or perhaps what we need consciousness for is fully
automated in them.
Although there are impressive examples of 'blind-sight' - where subjects with a damaged visual cortex can make visual discriminations better than a mere 'guess' - the blind-sighted are not totally unconscious.
Of course, sleeping and damaged brains are not doing their usual job of collecting, weighing and computing. But there is no reason to think that consciousness could be 'subtracted' from a brain that's doing its usual job successfully.
It is the organism with a
working brain and consciousness that normally faces the challenges
of the world.
They share with us the difficulties of moving, probing the environment, remembering, predicting the future and coping with unforeseen challenges.
If the same behavioral
and cognitive criteria are applied as to much larger-brained
vertebrates, then some insects are likely to qualify as conscious
agents - with no less certainty than cats or Descartes' dog.