The habit of smoking altered my response to deceit.

The results of the research were published in the journal Frontiers in Neuroscience and were also presented on November 20, 2024, at the DSC Europe 24 conference. In today's world of information overload, individuals must always stay alert and quickly adapt to changing conditions to avoid being deceived and falling into the trap of misinformation. Studying how humans cope with stress, whether they can recognize deception in challenging situations, and how their bodies and brains respond is becoming one of the crucial scientific tasks today.

A group of researchers from the National Research University Higher School of Economics and the Institute of Higher Nervous Activity and Neurophysiology of the Russian Academy of Sciences analyzed people's reactions to stress caused by mental strain and examined whether they could understand when they were being deceived.

The experiment involved 70 participants. The subjects completed memory and attention tasks, with the difficulty gradually increasing throughout the experiment. They were required to remember the position and color of balloons in an image and determine whether it matched a previous one. As the level of difficulty increased, the number of balloons and colors to remember also increased. After each response, participants were immediately informed of the result. In the middle of the experiment, they were misled; for instance, they were told they made a mistake even when their answer was correct.

Throughout the experiment, the researchers recorded body reaction parameters and the participants' pupil sizes. The pupil responds to changes in the sympathetic ("fight or flight") and parasympathetic systems (relaxation) and is directly linked to cognitive processes. During mental strain, it dilates. Using machine learning algorithms, the participants were divided into two groups based on how their pupils reacted to increasingly complex tasks.

Next, the authors of the experiment used machine learning to analyze a wide range of physiological and behavioral parameters to identify how the groups of participants differed. The analysis took into account questionnaire data about health status, chronic illnesses, lifestyle, bad habits (including smoking), and tendencies toward depression and anxiety disorders. During task completion, the participants' heart rates, skin electrical conductivity, and breathing (polygraph parameters) were measured. Additionally, the speed of task completion, the number of errors, and the level of self-assessment after the experiment were considered.

“We were the first to use the method of dynamic pupillometry, which measures pupil size, for the simultaneous analysis of a vast number of body and brain parameters, as well as psychological factors. Changes in pupil size directly indicate how a person adapts to a stressful situation: when they relax and when they mobilize. Thanks to technology, we were able to process the entire volume of data and identify patterns that would be impossible to discover manually,” says one of the study's authors Evgenia Alshanskaya, a junior researcher at the Institute of Cognitive Neuroscience.

The researchers obtained intriguing results: in one of the groups, participants exhibited a less pronounced response to stress and different heart and eye behaviors. They responded to questions more quickly but made more mistakes, resulting in a lower self-assessment of task performance. This group had a higher number of smokers and individuals prone to daytime sleepiness. These two parameters were statistically significant when comparing the two groups. The scientists suggest that this may be related to the effects of nicotine on the body.

“Nicotine affects acetylcholine receptors in the body and brain. Acetylcholine is the first discovered neurotransmitter, which helps control muscles, regulates heartbeat, breathing, pupil reaction, and plays a crucial role in cognitive processes. It influences how we react to and process information. When a person smokes, nicotine 'tricks' these receptors, causing them to function improperly. On one hand, nicotine relaxes, but on the other, it alters the connection between the brain and body, making it harder to respond correctly to stressful situations. For attention, we do not need relaxation and calmness; rather, we need optimal stress and tone,” explains Evgenia Alshanskaya.

According to the authors, daytime sleepiness may also be linked to nicotine's impact on nicotinic acetylcholine receptors. These receptors manage the activation and inhibition of neurons and modulate dopamine release and the functions of the dorsolateral prefrontal cortex, which is responsible for planning and executive functions. “Acetylcholine and its receptors are one of the most significant areas of contemporary neurobiological research,” the authors emphasize.

The results of the study once again highlight the strong influence of smoking on human health. The findings are also essential for developing individualized strategies to enhance cognitive resilience in the face of stress and information overload. Furthermore, they may be beneficial for educational and training purposes, as they clarify the understanding of optimal stress or optimal load for successful learning, working, and resilience in an unstable world.