If you and your partner disagree on how to load a dishwasher, whether 9 p.m. is a reasonable bedtime, or what constitutes a real emergency, don’t panic. A new study suggests most couples are built that way.

Research published in the Journal of Research in Personality analyzed data from 451 married couples in the Netherlands, with an average of 28 years together. Each partner completed a detailed personality questionnaire twice, once for themselves and once describing their spouse, across six dimensions covering ethics, emotional sensitivity, cooperativeness, conscientiousness, social boldness, and curiosity. The results were clarifying in the least romantic way possible.

Couples actually resembled each other in exactly two of those areas, moral values and curiosity, with similarity scores of 0.39 and 0.36. To put that in perspective, personality researchers consider a correlation above 0.30 meaningful, and most spousal similarity studies struggle to find even that. For emotional sensitivity, cooperativeness, conscientiousness, and social boldness, the scores sat near zero across the board.

Long-Term Couples Only Need to Be Similar in 2 Key Ways, New Study Finds

Spouses also overestimated how much they had in common, particularly regarding values. The assumed similarity score for ethics was 0.57, compared with a real score of 0.39. That distance makes sense when you consider that values are harder to observe day-to-day than habits or temperament. There’s no obvious tell for sincerity the way there is for, say, leaving dishes in the sink.

After decades together, couples were accurate at reading each other’s personalities, scoring higher than what has been found in younger couples. The average agreement score was about 0.70 across all six dimensions, and for curiosity-related traits specifically, accuracy climbed into the high 0.70s. The exception was ethics. Even after accounting for assumed similarity, accuracy for sincerity and modesty dropped to 0.51. Those traits are apparently harder to observe from the outside, even after three decades of shared life.

The study has limits worth noting. It drew entirely from heterosexual couples in the Netherlands, and prior research on Chinese couples found near-zero similarity across all personality dimensions. Whether these findings hold outside Western European contexts is an open question.

The data suggest that long-term compatibility is a smaller target than most people think. Two people can have entirely different temperaments, emotional wiring, and daily habits, and still build a lasting marriage. What seems to hold them together is a shared sense of right and wrong, and a mutual curiosity about how the world works.