Several years ago, Christian Rutz began to wonder if he was giving his crows enough credit. Rutz, a biologist at the University of St. Andrews in Scotland, and his team captured wild crows in New Caledonia and challenged them with puzzles made from natural materials before releasing them again. In one try, the birds faced a log with holes in it containing hidden food and could extract the food by bending a plant stem into a hook. If a bird didn’t try within 90 minutes, the researchers removed it from the dataset.
But, says Rutz, he quickly began to realize that he was not, in fact, studying the skills of New Caledonian crows. He was studying the skills of a single subset of New Caledonian crows who quickly approached a strange log they had never seen before – perhaps because they were particularly brave or reckless.
The team changed their protocol. They started giving the more hesitant birds an extra day or two to get used to their surroundings, then tried the puzzle again. “It turns out that a lot of these retested birds suddenly start engaging,” Rutz says. “They just needed a little extra time.”
Scientists increasingly realize that animals, like people, are individuals. They have distinct tendencies, habits, and life experiences that can affect their performance in an experiment. This means, according to some researchers, that much published research on animal behavior may be biased. Studies purporting to show something about a species as a whole — that green sea turtles migrate a certain distance, for example, or how finches respond to a rival’s chirping — can tell more about the individual animals that have been captured or housed in a certain way, or who share certain genetic characteristics. This is a problem for researchers seeking to understand how animals perceive their environment, acquire new knowledge and live their lives.
“The samples we take are quite often heavily biased,” Rutz says. “It’s something that’s been in the air for quite a long time in the community.”
In 2020, Rutz and his colleague Michael Webster, also at the University of St. Andrews, proposed a way to solve this problem. They called it STRANGE.
This video of one of Christian Rutz’s experiments shows a New Caledonian wild crow bending a hooked plant stem to retrieve food from a hole. Although some birds were initially hesitant to approach the materials, Rutz realized that many of them could solve the puzzle with more time.
CREDIT: BC KLUMP ET AL / BMC BIOLOGY 2015
Personalities are not just for people
Why “STRANGE”? In 2010, a article In Behavioral and brain sciences suggested that the people studied in much of the published psychology literature are WEIRD—from Western, educated, industrialized, wealthy, and democratic societies—and are “among the least representative populations one can find to generalize on humans”. Researchers could draw radical conclusions about the human mind when in reality they have only studied the minds of, say, undergraduate students at the University of Minnesota.
A decade later, Rutz and Webster, inspired by WEIRD, published an article in the journal Nature called “How WEIRD are your study animals?”
They proposed that their fellow behavioral researchers consider several factors regarding their study animals, which they termed Social History, Trappability and Self-Selection, Breeding History, Acclimatization and Habituation, Natural Changes in Responsiveness, Genetic Constitution and Experience.
“I started thinking about these kinds of biases when we were using mesh minnow traps to collect fish for experiments,” Webster explains. He suspected – and then laboratory confirmed — that more active sticklebacks were more likely to swim in these traps. “We are now trying to use nets instead,” says Webster, to catch a wider variety of fish.
It is trappability. Other factors that could make an animal more trapped than its peers, besides its activity level, include a bold temperament, lack of experience, or simply a greater thirst for bait.
Other research has shown that pheasants housed in groups of five performed better on a learning task (finding out which hole contained food) than those housed in groups of only three – this is the social milieu. Skip spiders bred in captivity were less interested in prey than wild spiders (breeding history) and bees better learned in the morning (natural changes in reactivity). And so on.
Biases in experiments can have surprising sources. In one study, pheasants performed better on a learning task when housed in large groups. (Credit: Budimir Jevtic/Shutterstock)
It might be impossible to eliminate all biases from a group of study animals, Rutz says. But he and Webster want to encourage other scientists to think about STRANGE factors in every experiment and be transparent about how those factors might have affected their results.
“We used to assume that we could do an experiment like we did in chemistry – controlling for one variable and changing nothing else,” says Holly Root-Gutteridge, a postdoctoral researcher at the University of Lincoln at the University of Lincoln. UK which studies the behavior of dogs. . But research has revealed individual behavior patterns – scientists sometimes call this personality — in all kinds of animals, from monkeys to hermit crab.
“Just because we haven’t given animals credit for their individuality or distinctiveness doesn’t mean they don’t have it,” Root-Gutteridge says.
This failure of human imagination, or empathy, spoils some classic experiences, note Root-Gutteridge and his co-authors in a paper 2022 focused on animal welfare issues. For example, psychologist Harry Harlow’s experiments in the 1950s involved baby rhesus macaques and fake wireframe mothers. They would have provided insight into how human infants form attachments. But given that these monkeys were torn from their mothers and kept in unnatural isolation, are the results really generalizable, the authors ask? Or do Harlow’s findings apply only to his particularly traumatized animals?
Looking for more copiers
“All this individual-based behavior, I think it’s really a trend in behavioral science,” says Wolfgang Goymann, behavioral ecologist at the Max Planck Institute for Biological Intelligence and editor-in-chief of Ethology. The newspaper officially adopted the STRANGE framework in early 2021, after Rutz, who is one of the journal’s editors, suggested it to the board.
Goymann did not want to create new obstacles for the already overburdened scientists. Instead, the review simply encourages authors to include a few sentences in their methods and discussion sections, Goymann says, explaining how STRANGE factors might bias their results (or how they accounted for such factors).
“We want people to think about how representative their study is,” Goymann says.
Psychological researchers have also questioned whether studies of a select group of people, such as Western university students, really say much about human beings in general. (Credit: Gorodenkoff/Shutterstock)
Several other journals have recently adopted the STRANGE framework, and since their 2020 paper, Rutz and Webster have held workshops, discussion groups, and symposia at conferences. “It’s become something bigger than what we can do in our spare time,” Rutz says. “We’re excited about it, really excited, but we had no idea it would take off the way it did.”
He hopes the widespread adoption of STRANGE will lead to more reliable discoveries about animal behavior. The problem of studies that cannot be replicated has recently received much attention in some other sciences, human psychology in particular.
Psychologist Brian Nosek, executive director of the Center for Open Science in Charlottesville, Virginia and co-author of the 2022 paper “Replicability, robustness and reproducibility in psychological sciences” in the Annual Journal of Psychology, argues that animal researchers face similar challenges to those focusing on human behavior. “If my goal is to estimate human interest in surfing and I’m conducting my survey on a beach in California, I’m unlikely to get an estimate that generalizes to humanity,” Nosek says. “When you replicate my investigation in Iowa, you cannot replicate my findings.”
The ideal approach, says Nosek, would be to gather a truly representative study sample, but that can be difficult and expensive. “The next best alternative is to measure and be explicit about how the sampling strategy may be biased,” he says.
This is exactly what Rutz hopes STRANGE will achieve. If researchers are more transparent and thoughtful about the individual characteristics of the animals they study, he says, others might be better able to replicate their work — and make sure the lessons they learn from their animals of study are significant, and not quirks of experimental setups. “That’s the ultimate goal.”
In his own experiments with crows, he doesn’t know if giving more time to more shy birds changed his overall results. But it gave him a larger sample size, which may mean more statistically robust results. And, he says, if studies are better designed, it could mean fewer animals need to be captured from the wild or tested in the lab to reach definitive conclusions. Overall, he hopes STRANGE will be a victory for animal welfare.
In other words, what’s good for science might also be good for animals — seeing them “not as robots,” says Goymann, “but as individual beings who also have value in themselves. “.
10.1146/knowing-030923-1
Elizabeth Preston is a freelance science journalist who lives in the Boston area with her family and is working on a book about the evolution of parenthood. She suspects her trapping ability is average.
This article originally appeared in Knowable magazine, an independent journalism venture of Annual Reviews. You can read the original here.