Twelve astronauts who spent 4 to 7 months aboard the International Space Station showed a striking psychological pattern during flight. Scores tied to power and hedonism rose early in the mission, then eased later. Scores tied to benevolence and security moved the other way, dropping during the middle stretch before climbing again near the end and after landing. The same study also found that perceived mismatch in seven kinds of personal values was linked to higher interpersonal tension inside the crew.
The results come from a 2026 PLoS ONE study by Gro M. Sandal and Nathan Smith. The researchers asked the astronauts to complete the Crew Values Questionnaire package repeatedly across their missions. They tracked personal values, each astronaut’s sense of value agreement with crewmates and how much tension seemed to come from those perceived differences. For readers who follow human spaceflight, the paper pushes the discussion past the usual focus on bones, muscles and sleep. It asks how motivation shifts when people live in orbit for months and how those shifts may affect daily relations in a sealed workplace.
Numbers like these draw attention because the study reached beyond a simple claim that long missions feel stressful. The paper points to a more specific social problem. A crew can stay highly trained, deeply committed to the mission and still feel friction if members begin to read one another’s priorities differently. In a station where work, rest, privacy and small habits all happen in close quarters, perceived value distance can become part of the crew environment.
What changed during the mission
Universalism, benevolence and tradition started out as the most concordant values in the group overall, according to the abstract. In plain language, the astronauts generally saw themselves as aligned on broad human concern, care for other people and respect for shared norms. That baseline matters because it shows the crew did not begin the mission from a place of obvious social fracture.
Midmission brought the clearest movement. The abstract says scores for hedonism and power increased early in flight and declined later, while benevolence and security decreased and then rose again toward mission end and into postflight. Hedonism in value research usually refers to comfort, enjoyment and immediate satisfaction. Power refers to status, control, or influence. Benevolence refers to concern for close others and supportive conduct. Security points to safety, order and stability. The pattern suggests that astronauts’ motivational balance did not stay fixed while they were in orbit.
Readers should keep the interpretation cautious. The paper does not say astronauts became selfish in space and it does not say a temporary rise in power erased the more prosocial values that remained important overall. A safer reading is that long missions may shift which motives move closer to the front of attention at different phases. Early adaptation, the grind of the middle period and the approach of return to Earth may each pull on the crew in a different way.
Why shared values can affect crew tension
The most behaviorally important result may be the link between value incongruence and tension. The authors report that perceived incongruence in seven out of eight personal values significantly predicted interpersonal tension. That finding does not mean every disagreement led to open conflict. It means that when astronauts sensed a larger gap between their own priorities and those of crewmates, the odds of tension rose across most of the value domains the study examined.
Perceived mismatch can matter in small ways long before a crew argument becomes visible to outsiders. One person may read another crewmember’s push for efficiency as healthy mission focus, while someone else may read the same behavior as status seeking or indifference to group comfort. A wish for privacy may look like emotional self-management to one astronaut and withdrawal to another. A strong preference for routine may feel reassuring to one person and rigid to someone else. The paper gives those everyday interpretations a measurable frame.
Broader evidence from a systematic review of long-distance space mission analogs helps explain why the issue deserves attention. That review found that all teams in the comparable conflict data had reported at least one conflict by about 40 percent of mission completion, or 90 days. The ISS study adds a more precise human factor to that picture. Conflict risk in isolated crews is not only about workload or fatigue. The way crewmembers interpret each other’s motives may also be part of the story.
How the researchers measured values in orbit
The study followed a repeated-measures design rather than relying on one interview after landing. Astronauts regularly completed the questionnaire package during flight and into post-mission. That matters because values and tensions can drift over time and a single survey would miss the rise and fall that the abstract reports. A mission is not one emotional block. It has phases, each with its own demands, mood and social texture.
Perceived value congruence also followed a curve. The abstract says differences in achievement, power and benevolence decreased and then increased across mission phases. One possible reading is that crews may feel more aligned after settling into orbit, then notice differences again as time accumulates, energy changes and anticipation of return grows. The paper stays at the level of association, which is the right level for a sample of 12 astronauts. Even so, the pattern is useful because it highlights timing rather than treating the whole mission as socially uniform.
The method still has limits. A sample of 12 is valuable in space research, where human subjects are scarce, yet it remains a small group. The results also rely on self-report, which captures perception rather than objective truth about another person’s motives. Perception is still crucial in a crew setting, because astronauts respond to what they think others value. A misunderstanding can carry operational weight even when nobody is acting in bad faith.
What agencies can learn before Mars-class missions
NASA’s human spaceflight program already frames long missions as a mix of engineering, biology and daily life support. Its Living in Space overview says astronauts must manage nutrition, health risks and the broader challenges of life off Earth for extended periods. The new study adds another layer to that operational picture. A crew may also need help noticing how priorities shift through time, especially when the same behavior can be read in more than one way.
Pre-mission preparation is the most direct implication. The authors argue that training and in-flight support should target shifts in motivational sources and manage interpersonal tensions arising from value diversity. That recommendation sounds practical rather than abstract. Crews can train on technical procedures, communication rules and emergency drills; they can also train on how to talk about standards for privacy, recognition, mutual support, personal autonomy and what counts as fair behavior when everyone is under strain.
Longer exploration missions raise the stakes. NASA’s astronaut program is preparing crews for work on the station, at the Moon and eventually farther out. A Mars-class mission would stretch duration, delay communication and reduce easy access to ground support. Under those conditions, a crew that understands its own shifting priorities may have one more tool for staying effective. The ISS paper does not claim that value shifts alone determine mission success. It shows something more grounded and useful: motivational priorities can move during flight and perceived differences across those priorities can help explain where interpersonal tension begins to build.
