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Stress diminishes our capacity to sense new dangers

Being under stress makes us worse at detecting new dangers, according to a new study. 

Contrary to the common belief that stress puts our bodies on high alert, this new research from New York University demonstrates that stress can make our thinking and responses less flexible, so we are slower to learn new dangers. 

Researchers from New York University taught their subjects cues for danger, then put half of that group under stress. 

The cues for danger and for safety were then switched, and the study found that those exposed to stress adapted to the new cues more slowly than their peers. 

Stress can make us slower to react to new dangers in our environment, a new study shows. Its lead author, Candace Raio says that stress distracts us, and makes us less sensitive to changes in our environment, like an oncoming car

Our immediate ‘fight or flight’ responses to stressors are meant to help us take action when we’re in danger. 

But this new study, led by Dr Candace Raio, shows that when we’re already under stress, we are slower to learn that something that once was safe is now a danger. 

‘We thought it would take longer to learn something was safe that had been threatening, but found the opposite,’ she says.

In the first round of the test, none of the subjects were under stress, and they were all shown a series of images. Half of those images predicted a small electrical shock, while half did not. 

After half of the subjects had been subjected to stress, everyone watched the images again, but this time the dangerous and safe cues were switched. 

The subjects that had been put under stress – by holding one arm in a tub of ice water before doing the danger activity again – were even slower to learn that something that had been safe was now dangerous than they were to learn the reverse. 

 When you’re under stress and ramped up, you’re not paying enough attention to what’s going on around. You’re just not changing or updating your response.

Dr Candace Raio, New York University

This poses a greater risk to the stressed subjects. If you keep believing that a tiger is dangerous after it has become safe, and keep running from it, you’re wasting energy, but you’re not at a greater risk for not having changed your perception.

But it took the stressed subjects an average of six extra tries to catch up to the physiological responses of their unstressed peers. ‘What if in one of those six extra trials, the tiger is chasing you?’ asks Dr Raio. 

The experiment revealed how stress affects a learning variable called associability. ‘This is when unexpected things happen in my environment, and I think “that’s a problem, I have to learn this,”‘ she says. 

But stress is distracting, even when the changes to the environment are ones that should prompt a stress reaction themselves.

‘When you’re under stress and ramped up, you’re not paying enough attention to what’s going on around. You’re just not changing or updating your response,’ says Dr Raio. 

The study used a physical stressor, the ice baths. 

‘You could argue that the kinds of stress we’re encountering in day-to-day life, psychological stresses, are more distracting,’ says Dr Raio. 

One of the ways her team team gauged the physiological fear responses of the subjects was through the levels of two hormones released in response to stress. 

They found that these levels were comparable to those of other studies that looked at chronic or ‘trait’ stress and acute stress. 

‘This is all honing in on the idea that when you’re under chronic stress or other stress, you just aren’t adapting as well,’ Dr Raio says. 

Eventually, she notes, the subjects that were stressed out did ‘catch up,’ and have the same physiological responses, but the message was clear that ‘reducing stress levels actually is really important to being able to function in an adaptive way.’ 

This study only examined passive responses to cues for danger, such as production of noradrenaline, the ‘fight or flight’ hormone, so it’s unclear how the subjects would have responded if there was an action to take to avoid the danger.  

‘Maybe stress would prime you to run, but if next time something that was safe now predicts a tiger, that would be hard to change,’ says Dr Raio. 

She wonders if those ‘who are used to a “volatile” environment, always on the move always used to things changing, would maybe be more resilient.’ 

But, conversely, we are constantly inundated by stimulation and news of a changing world, which could be exactly the kind of stress that distracts us from noticing changes in our tangible environment, like an oncoming car.

‘Exposure to social media and things…you could argue that you have access to changes of the world more frequently, so stress could change your ability to integrate changes of information and things going on around you,’ says Dr Raio.