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Can Insects, Bacteria, and Plants Have Personalities Too?

If personality amounts to observed individual differences in behavior, the answer is yes, though the issues are more complex for plants

Yesterday, we looked at a paper in which researchers reported that marmosets (a South American monkey) have personalities. Most of us would simply assume that they do and we are right to think so. Research on many vertebrate animal species shows that even reptiles and fish have personalities. Of course, the number of dimensions a vertebrate’s personality can have varies with its intellectual and lifestyle complexity.

But now, what about the vast world of the invertebrates, the life forms whose body is not organized around a spinal cord terminating in a brain? Their body plans can vary from that of a starfish through to a honeybee. Can they have personalities, despite very different brain arrangements, including — in some cases — no brain and no obvious equivalent of a brain? Let’s see what the research says:

Octopus: Many invertebrates (animals without a central nervous system organized around a spinal cord ending in a brain) do not appear to have or need much individual intelligence. But the octopus is so much of an exception that it has been called a “second genesis” of intelligence. A recent film, The Octopus, My Teacher, features a man who strikes up a sort of friendship with an octopus.

Jennifer A. Mather, writing in Natural History (February 2007),
recounts, “… I learned, their behavior is quite complex and variable. I watched as they carefully chose rocky crevices for their dens and blockaded the entrances with piles of rocks. I observed them navigate complicated routes across the sea bottom to and from their hunting grounds. But I was most intrigued to discover that individual octopuses are very different from one another.”

This is despite a short lifespan and a rather tragic social life: After mating, “The female remains in her den and refuses all food during the 78 day incubation period. She stays with her eggs until they hatch and then dies. After mating, the male loses his ability to camouflage and loose his will to live and eventually dies from starvation.” (Octopuses — “Characteristics, Behavior, and Intelligence”)

Insects: With social insects we face a different question. We are dealing with the hive mind. As J. Scott Turner shows in Purpose and Desire, a termite mound has a hive mind “a communal brain with no specific physical location.” Ants, bees, and termites cooperate in huge numbers to get a job done, all seemingly sharing one “mind” which is still little understood:

Still, bees, which have been studied, show some differences in personality: “The findings offer a new window on the inner life of the honey bee hive, which once was viewed as a highly regimented colony of seemingly interchangeable workers taking on a few specific roles (nurse or forager, for example) to serve their queen. Now it appears that individual honey bees actually differ in their desire or willingness to perform particular tasks, said University of Illinois entomology professor and Institute for Genomic Biology director Gene Robinson, who led the study. These differences may be due, in part, to variability in the bees’ personalities, he said. ” (Phys.org, March 8, 2012)

And ants? “Individual ants have differences in behaviour – something almost akin to a personality – that affect colony decisions… But the team found a lot of variability between the amount of time individuals spent in a nest of a certain quality”:

“Some ants are picky, others are more liberal and will accept almost anything,” says O’Shea-Wheller. “Much like humans, not everyone wants to live in a mansion.”

And some ants never seem happy, however nice a nest is. They live there, but seem restless, and are more likely to scout.

Chris Simms, “Ant choosiness reveals they all have different personalities” at New Scientist (February 1, 2017)

Beetles, which are generally non-hive insects, display personality, according to researchers: “By performing behavioral tests analogous to vertebrate assays repeatedly during adult life, we identified 3 personality dimensions, boldness, activity, and nontargeted explorativeness.” (Behavioral Ecology, 2013)

Cockroaches have been shown to have individuality in terms of learning and memory (2019) Crickets differ individually in terms of aggression and boldness. Firebugs differ individually as well. These are simple traits, to be sure, but no one is claiming that insects have complex minds. The question is whether they can show individual differences (personality). It seems that they can. So can spiders (which are not insects), who, having a type of intelligence, also differ individually along the same simple scales.

Bacteria: Surely not bacteria! Well, from Quanta we learn that even single cell life forms can show surprising individuality. A recent experiment assumed that “a pack of cells that started the race at the same time would in theory all finish around the same time”:

But that’s not what Salek and Carrara found. Instead, some bacteria raced through the maze substantially more quickly than others, largely because of varying aptitude for moving toward higher concentrations of food, a process called chemotaxis. What appeared to Salek and Carrara as a mass of indistinguishable cells at the beginning was actually a conglomerate of unique individuals…

This bacterial individuality — known more technically as phenotypic heterogeneity — upends decades of traditional thinking about microbes.

Carrie Arnold, “Bacterial Clones Show Surprising Individuality” at Quanta

So, as we saw with vertebrates, the number of scales on which personalities can differ likely depends on intellectual endowments. Put another way: The bacterium has simple relationships and problems compared with those of a chimpanzee in a troupe. But within its own environment, the bacterium shows individual responses.

Now let’s take a deep dive: What about plants? — an entirely different kingdom of life, where nervous systems do not end in brains or anything like them:

Plants: In the past, plants were not assumed to have the needed intelligence to communicate but in fact they do. They have nervous systems and, like mammals, they use glutamate to speed transmission. They communicate extensively by releasing chemicals into the air or the ground but they are not considered to be capable of consciousness, which involves far more than the ability to communicate via chemical signals.

But one botanist, Rick Karban, argues that they do have personalities in terms of individual behavior differences:

Up to this point in contemporary botany, individual plants within a species have been seen as replicants. No individual trait has mattered, and only the average of the population would count. Any individual variation that fell outside a trend line was considered noise.

Personality research, however, treats that noise as valuable data, seeing a spectrum of behavior where traditional botany sees only a mean and median…

The way Karban imagines plant personalities function is like how humans behave—say, during a pandemic. “If you have variation in how anal people are about washing their hands, you might have some individuals who are hyper hygienic, and under certain conditions”—such as the ones we’re living under right now—“they might have an advantage over individuals who are really cavalier,” he says. But the same trait may not always be the winning strategy. “Under other kinds of conditions, being that person would be selected against,” Karban says. An excessive focus on hygiene is also connected to certain psychological disorders; at the population level, it is linked to allergies.

Zoe Schlanger, “The Botanist Daring to Ask: What If Plants Have Personalities? ” at Bloomberg Quint (November 21, 2020)

If so, “personality” in plants comes down to what it does in bacteria: differences in individual behavior along a limited spectrum. But up till recently, few knew that plants even communicated, let alone that their behavior could differ individually.

We live in a world full of intelligence, so perhaps we should not be so surprised. As British writer G.K. Chesterton (1874–1936) pointed out some years ago, “We talk of wild animals but man is the only wild animal. It is man that has broken out. All other animals are tame animals; following the rugged respectability of the tribe or type.”

Chesterton is surely right here. A great many animals have been found by researchers to have personality and possibly even plants do too. But only human beings have reason, which is why only human beings speak a language full of abstractions and images and arguments about fairness and moral choice.

So we are like the other animal life forms we’ve looked at in that we have personality. But we are unlike them in that we have that inexplicable extra ingredient, sometimes called the soul, which is why our communications are so different. It’s something to think about as we contemplate a much more complex world than we perhaps expected to find.


You may also wish to read: Why do researchers wonder whether animals have personalities? Every friend of dogs, cats, or birds knows what some struggle to prove. Let’s take a look at what they found. Mammals, birds, and reptiles differ by ability but those that have been studied seem to have individual personalities within the frame of their intelligence.

and

Your soul has no “off switch.” A major modern misunderstanding of the human mind is to assume that it is like a machine with an “on” and an “off” switch. (Michael Egnor)


Denyse O'Leary

Denyse O'Leary is a freelance journalist based in Victoria, Canada. Specializing in faith and science issues, she has published two books on the topic: Faith@Science and By Design or by Chance? She has written for publications such as The Toronto Star, The Globe & Mail, and Canadian Living. She is co-author, with neuroscientist Mario Beauregard, of The Spiritual Brain: A Neuroscientist'€™s Case for the Existence of the Soul. She received her degree in honors English language and literature.

Can Insects, Bacteria, and Plants Have Personalities Too?