Scientists have discovered why stress sometimes shuts down logic

The work was published in Science Advances.

Scientists studied how stress affects the hippocampus - an area of the brain that is involved in memory, learning and linking different events into a bigger picture. It turned out that stress did not stop learning, but prevented the brain from "bringing up" old memories the moment a person learnt something related to them.

Simply put, in a calm state, the brain sees connections: 'this event is related to something I already know'. And under stress, it is more likely to see similar events as separate files. Therefore, the logical chain is broken.

Details

The study involved 121 healthy volunteers. The experiment lasted two days. On the first day, the participants were shown pairs of images: for example, a face or a scene together with a certain animal. In this way, the brain had to memorise the connection between the two objects.

On the second day, some of the participants were stressed using the Trier Social Stress Test. This is a laboratory procedure where a person undergoes a simulated stressful situation: for example, a job interview and complex verbal calculations. The control group performed calmer tasks. After that, all participants were studied again, but in a different way: the same animal was paired with a new object.

The researchers then tested whether people could make an indirect inference. If on the first day a person remembered the connection "A - B" and on the second day "B - C", then later he had to understand the connection between "A" and "C", although these two objects together were not shown to him.

This is where stress played a key role. People under stress were worse at linking old and new information. They could learn new pairs, but they had a harder time using their previous memory to infer the hidden connection.

Brain scans showed that in calm participants, the hippocampus automatically reactivated old memories during new learning. In participants after a stressful session, this reactivation was weaker. The worse the brain was at "remembering" the old part of the chain, the worse the person performed at inference.

The scientists also saw another effect: under stress, the hippocampus more strongly separated related events, rather than united them. That is, it was as if the brain was spreading the information out into different folders rather than collating it into one story. In Nature's retelling, this result is described as a possible explanation for why, under pressure, people find it harder to show insight and connect past experiences with new information.

Why it matters

The study helps explain a familiar situation: a person can know everything but fail to apply the knowledge in a stressful moment. This happens in an exam, a job interview, during an urgent decision at work or when under pressure in a conflict situation.

This does not mean that stress always "switches off the brain". It can affect memory in different ways. In some cases, stress can help you better retain a vivid event. But it can be harder to use information flexibly, connect facts, and draw conclusions under stress.

Inference is important for education, work, and the practice of law. For example, stress can affect how a student solves a problem, how an employee makes a decision under pressure, or how a witness connects details of events during an interview. The authors explicitly state that the results may have implications for educational, legal, and clinical contexts.

Background

The hippocampus is often referred to as one of the centres of memory. But it doesn't just store memories. It helps link individual events to each other: where it was, what it was related to, what inference can be drawn from past experiences.

This ability is called memory integration. Thanks to it, a person does not just remember disparate facts, but builds a system from them. For example, if you know that an acquaintance bought a blue car, and then you see that car outside the library, you can conclude that the acquaintance is probably inside. This is not a direct recollection, but an inference based on the relationship between events.

A new study shows that acute stress disrupts this very mechanism. The brain continues to receive information, but is worse at linking it to existing memories. Therefore, "logic" under stress may suffer not because the person knows nothing, but because the brain finds it harder to assemble what is known into a coherent picture.

Source

Research: Kai A. Schüren, Nicole Varga, Hendrik Heinbockel, Alison R. Preston, Benno Roozendaal, Lars Schwabe, "Stress disrupts hippocampal integration of overlapping events and memory inference in humans", Science Advances, 2026.