# Twenty-five astronauts took 10 thinking tests before, during and after 6-month ISS missions and most scores stayed steady while early flight slowed attention, working memory and some processing speed tasks

> Twenty-five astronauts completed a broad set of cognitive tests across five mission phases tied to roughly six months aboard the International Space Station and the main result was reassuring: overall performance stayed fairly stable. The clearest changes appeared early in flight, when...

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Byline: ARGO.net Editorial Team
Published: 2026-08-04T17:10:02+00:00
Categories: Explainer, Space

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Twenty-five astronauts completed a broad set of cognitive tests across five mission phases tied to roughly six months aboard the **International Space Station** and the main result was reassuring: overall performance stayed fairly stable. The clearest changes appeared early in flight, when a few tasks that depend on quick responses, **working memory** and **sustained attention** became slower.

Across pre-flight, early flight, late flight, early post-flight and late post-flight testing, the researchers behind a [Frontiers in Physiology study](https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2024.1451269/full) did not find evidence for a broad collapse in cognition during current low Earth orbit missions. Their dataset, led by **Sheena I. Dev** and colleagues, instead points to a more specific pattern: high-performing professional astronauts usually kept their accuracy, while a narrower group of tasks showed slower speed at certain points in the mission.

For crews who have to manage complex schedules, equipment and safety procedures, that distinction is useful. A stable overall picture in **low Earth orbit** supports current ISS operations, while the slower early-flight scores highlight moments when planners may want extra care around heavy workloads, time pressure, or tasks that depend on sharp attention.

## What stayed steady in orbit

The study followed astronauts from ages 33 to 61 and looked across 10 parts of the **Cognition Battery**, a computerized testing system designed for repeated use in high-performing groups. Summary speed and summary accuracy stayed close to baseline across the mission, which fits the paper's central conclusion that six-month ISS stays did not produce a systematic decline across the full range of measured abilities.

Several individual tasks were also steady from one phase to the next. Visual learning, visual memory and line orientation showed no clear mission-wide slide. Accuracy remained stable on many tests even when speed changed, which means astronauts were often still getting answers right while taking a bit longer on selected tasks. The public [PubMed record](https://pubmed.ncbi.nlm.nih.gov/39633651) reflects the same broad pattern in its abstract.

Readers should treat that balance carefully. The measured effects during current ISS missions were selective, generally mild at the group level and linked to certain phases rather than a steady downward march from launch to landing.

## Where the slowdowns appeared

The clearest changes clustered around the early part of the mission. On the Fractal 2-Back test, which tracks nonverbal working memory, astronauts were slower in early flight and stayed slower through later phases. On the Digit Symbol Substitution Task, a measure connected to scanning and processing speed, performance also slowed during flight and remained slower in early post-flight than at baseline.

A shorter-lived effect appeared on the **Psychomotor Vigilance Test**, a standard measure of sustained attention. Scores were slower in early flight, then the gap did not persist in the same way. The pattern fits a simple operational idea: the first stretch in orbit may demand adaptation to microgravity, sleep shifts, packed schedules and the constant novelty of life aboard the station.

The researchers also found a drop in **risk-taking propensity** later in flight and after return, based on the Balloon Analog Risk Test. Lower risk tolerance does not automatically mean worse judgment. It shows that willingness to keep pushing for reward changed over time and the paper treats that shift as a result worth tracking rather than a failure signal.

Even with these changes, the study stayed conservative. About 11.8 percent of all in-flight and post-flight scores landed at least 1.5 standard deviations below the sample's baseline mean and the highest shares came from working memory, processing speed, sustained attention and the balloon risk task. Those figures show that some lower scores do occur, yet they still sit inside a broader picture of stable group performance for most domains.

## How the team measured cognition

The project was part of the **NASA Human Research Program** Standard Measures Cross-Cutting Project and each astronaut was tested once before launch, twice during the mission and twice after landing. The authors corrected for practice effects, which is crucial in repeat testing because people often improve simply from seeing the same kind of task again. Their methods also used z-scores to compare each mission phase with the group's pre-flight baseline.

The battery itself covered visual learning, memory, abstract reasoning, emotion recognition, line orientation, sensorimotor speed and more. An earlier [Cognition Battery spaceflight report](https://doi.org/10.3389/fphys.2021.643854) and the related [NASA Life Sciences Data Archive](https://nlsp.nasa.gov/view/lsdapub/lsda_experiment/ea3997a6-1093-5e0f-8f54-47684d4f1e73) help place the new work inside a longer effort to measure human performance in space with the same tools across missions and studies.

Method details also explain why the paper carries weight. Twenty-five astronauts is still a modest sample by many Earth-bound standards, yet it is large for this kind of repeated in-flight testing. The authors describe their baseline table as a preliminary normative dataset for professional astronauts, which could help future teams spot unusually low scores against a better reference than isolated single-mission observations.

## Why the limits still matter

The new findings are encouraging for present-day ISS operations, though they do not settle the deeper question of what will happen on longer missions farther from Earth. The paper itself contrasts its results with the [NASA Twins Study](https://doi.org/10.1126/science.aau8650), which followed one astronaut through about 340 days in space and reported broader post-flight cognitive changes. Duration, radiation exposure, mission stress and operational demands may all look different beyond the ISS.

The authors also explored sleep and self-rated alertness and they found no clear overall pattern linking those reports to performance across the battery. Caution is still warranted here. Self-reported sleep is a blunt measure and the study did not capture every strain that can affect thinking, such as workload spikes, exercise demands, nutrition, stress tied to specific operations, or the unusual demands of future deep-space timelines. NASA's public [technical record](https://ntrs.nasa.gov/citations/20250000373) for the paper makes the study easy to trace for readers who want the formal citation trail.

Future exploration missions will test whether the same resilience holds when crews face longer isolation, greater distance from Earth and harsher radiation environments. For now, the most defensible reading is narrower and still valuable: current six-month ISS missions appear compatible with stable overall cognition in professional astronauts, while early-flight slowdowns in a few key domains deserve attention when crews are adapting to orbit.