Stress may diminish our ability to sense new dangers

Contrary to the conventional view that stress enhances our ability to detect sources of threat, a team of researchers have found that it diminishes the ability to predict new dangers.

The research indicated that stress reduces physiological response to the new threat cue.

The researchers applied a computational learning model to further understand how stress affects flexibility in decision-making. This analysis revealed a learning deficit for the subject put under the stress condition that participants used to update the cue associations. In short, this resulted in a slower rate of learning.

"Our study shows that when we are under stress, we pay less attention to changes in the environment, potentially putting us at an increased risk for ignoring new sources of threat," said lead author Candace Raio, a postdoctoral researcher at New York University.

The researchers conducted a series of experiments to test the ability to learn to flexibly update threat responses under stressful conditions.

Here, the participants viewed images on a computer screen. 

The appearance of some images were coupled with a mild, electric wrist-shock.

Half of the participants underwent a laboratory procedure a day later designed to induce stress. This "stress group" placed their arm in an ice-water bath for a few minutes, which elevated the two stress hormones -- alpha-amylase and cortisol. 

later, all the participants repeated the threat-conditioning procedure. However, this time the cue outcomes switched. The earlier threatening cue no longer predict shock, but the formerly safe cue did.

While the participants viewed the images, the researchers collected physiological arousal responses in order to measure how individuals anticipated the outcome of each cue.

On the second day, the "stress group" was less likely to change their responses to threats than the control group. 

The research published in the journal Proceedings of the National Academy of Sciences suggested that participants did not fully switch their association with this cue from safe to threatening.