Hot Temperatures Made Australian Lizards Grow Up to Be Stupider. Are Humans Next?

Bearded dragons that have been nested in warmer environments aren't as smart as those in cooler environments.

The eggs of 13 of this species of Australian lizards were incubated in two different environments that had a difference of 3 degrees Celsius (30 and 27 degrees Celsius, or 86 and 80.6 degrees Fahrenheit), which is currently how much higher global temperatures are on track to rise. When they were around one year old, researchers tested their ability to learn from other lizards to perform new tasks. Researchers had the lizards watch a video of an unfamiliar female lizard open a sliding door to receive food from behind the door. After watching the video, lizards had five minutes to open the door to retrieve the food themselves.

The study, published Wednesday in Royal Society's Open Journal, revealed that the group that was incubated in the cooler environment completed the task significantly quicker—around twice as fast.

"Environmental change is one of the key issues affecting habitats worldwide, creating challenges for animals living there," Anna Wilkinson, a co-author on the study and an animal cognition and behavior professor at the University of Lincoln's School of Life Science, in the United Kingdom, said in a statement. "One of the first responses an animal can make to a changing environment is changing its behavior. Cognitive abilities are likely to be critical to how they adapt because they influence how an animal perceives, stores and uses information from the surrounding environment.

"Bearded dragons inhabit arid areas in Australia and, as such, climate change is likely to have a profound impact upon the environment in which they live," Wilkinson told Newsweek in an email.

Wilkinson added that these findings suggest that the incubation environment may choose certain traits to adapt to the specific environment that an animal is born in. "For example, a cooler environment may produce animals that are better adapted to survival in that temperature profile and vice versa," Wilkinson said. Further research would be required to test those ideas, the authors concluded.

The study is a telling example of how warming temperatures affect all animals—and that includes humans.

Multiple studies a few years ago showed that people in warmer surroundings were not as good at proofreading a paper and complex decision making, reported the Scientific American, though the results do not mean that people in warmer climates make poorer decisions than those in cooler environments. Humans are quite adaptable to new temperatures. That research suggests that slight changes in temperature from what people may expect is what makes the difference.

Bearded dragons that were incubated in the cooler environment completed the task significantly quicker—around twice as fast—a new study has revealed. Getty

Last year, the U.S. Global Change Research Program (which also released a climate change report earlier this month), noted that mental health could be negatively impacted by climate-related disasters. Though unrelated to how hot temperatures could affect humans' cognitive ability, the findings are relevant for understanding how humans' mental health will be affected by global rising temperatures.

Post-traumatic stress disorder, depression and anxiety are often experienced by those who have lived through natural disasters. A majority recover, the report says, but a significant proportion develop a chronic mental health issue. Children, the elderly, women, people with pre-existing mental illnesses, the economically disadvantaged, the homeless and first responders are particularly vulnerable to distress and other mental-health consequences as a result of climate-related or weather-related disasters.

Bearded dragons rest at La Unica farm in La Herradura, 40 kilometers south of San Salvador, El Salvador, on May 22, 2009. Bearded dragons that have been nested in warmer environments—even by 3 degrees Celsius—aren’t as smart as those in cooler environments. Getty

Those with mental illnesses, the elderly and those taking medications that impair the body's ability to regulate its temperature are also at a higher risk of poor physical and mental health due to extreme heat. Extreme heat can also be deadly: One recent study documented all the ways heatwaves could kill people biologically, and it counted 27.

There is a silver lining in this study's findings, at least. The bearded dragons could adapt to the changing environments.

"This flexibility of cognitive ability could aid reptiles in adapting to new, changing environments and could offer a potential buffer in the face of human-induced environmental change," Harry Siviter, a research assistant at Royal Holloway, University of London, said in a statement. "However, if conditions change too rapidly, then reptiles might struggle to adapt quickly enough to their changing environments, which could negatively influence their survival."