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3.5 Growth Trajectories

Two people meet. They’re compatible. They fall in love. Five years later, they’ve become different people—and sometimes those new versions aren’t compatible anymore.

The question isn’t just “Are we right for each other now?” It’s “Will we still be right for each other as we both change?”

Research on personal growth in relationships reveals what helps couples evolve together rather than apart.

Self-Expansion: The Growth Engine

One of the most robust findings in relationship science is self-expansion theory: we’re motivated to grow and expand our capabilities, and close relationships are a primary vehicle for this growth.[1]

When you fall in love, you literally expand your sense of self. Research shows people who fall in love experience:[2]

  • Increased self-concept diversity
  • Greater self-efficacy
  • Incorporation of partner’s resources, perspectives, and identities into their own

This isn’t metaphor—it’s measurable. The Inclusion of Other in Self (IOS) scale shows how much people have integrated their partner’s identity with their own.[1]

The implication: healthy relationships facilitate personal growth. When growth stops, relationships often stagnate.

Perceived Similarity Matters More

Here’s the interesting finding about growth compatibility: perceived similarity in values predicts relationship quality better than actual similarity.[3]

In early relationships, being objectively similar helps attraction. But once you’re established, what matters is whether you feel aligned—even if you’re not actually that similar.

This means couples can diverge in objective ways while maintaining the perception of growing together. The story you tell about your shared trajectory matters.

Growth Mindset in Relationships

Carol Dweck’s research on growth mindset extends to relationships:[4]

Destiny beliefs: Relationships are either “meant to be” or they’re not. Compatibility is fixed.

Growth beliefs: Relationships can be cultivated through effort. Challenges are opportunities to develop together.

Research shows growth beliefs predict:[4][5]

  • Better coping with relationship challenges
  • Greater persistence through difficulties
  • Longer relationship duration
  • Slower decline in satisfaction over time

Destiny-oriented individuals abandon potentially salvageable relationships when challenges arise. Growth-oriented individuals work through them.

A longitudinal study of 300 couples found stronger destiny beliefs predicted higher initial satisfaction, but higher growth beliefs predicted slower decline over time.[5]

Supporting Partner Growth

How you respond to your partner’s growth pursuits significantly affects both individual and relationship outcomes.

Research on partner support for self-improvement found:[6]

  • Supportive responses predicted both relationship quality AND actual self-improvement success
  • Effects persisted over one year
  • Nurturing and action-facilitating support was most helpful
  • Criticism and invalidation undermined both relationship quality and personal growth

Another landmark study on secure base support found:[7]

  • Partners who provide responsive (non-intrusive) support for exploration enhance their partner’s happiness, self-esteem, and goal attainability
  • This support facilitates personal growth while strengthening the relationship bond

The key is supporting autonomy—helping your partner grow in their own direction, not the direction you’d prefer.

Goal Coordination

Couples with aligned goals fare better—but research shows the mechanism matters.

A study of older couples found:[8]

  • Goal coordination predicted better goal progress
  • It also predicted lower physiological stress
  • And higher relationship satisfaction
  • Discrepancies between assumed and actual joint goals hindered progress

A longitudinal study of 148 couples found goal coordination increased goal attainment, which increased life satisfaction for both partners.[9]

The implication: don’t just assume you know your partner’s goals. Explicitly discuss them. Coordination requires communication.

Capitalization: Celebrating Success

How you respond to your partner’s good news matters as much as how you respond to their problems—maybe more.

Research on capitalization (sharing positive events) found:[10]

Response StyleDescriptionEffect on Relationship
Active-ConstructiveEnthusiastic, engaged supportStrengthens bond
Passive-ConstructiveUnderstated acknowledgmentNeutral
Active-DestructivePointing out downsidesDamages relationship
Passive-DestructiveIgnoring or changing subjectDamages relationship

Strikingly, responses to positive events better predicted relationship well-being than responses to negative events.[11]

When your partner shares good news about a promotion, opportunity, or achievement:

  • Active-constructive: “That’s amazing! Tell me all about it. What happens next?”
  • Passive-constructive: “That’s nice.”
  • Active-destructive: “That sounds like a lot more work. What about our weekends?”
  • Passive-destructive: “What should we have for dinner?”

How you celebrate together shapes whether you grow together.

The Suffocation Model

Modern relationships face a unique challenge. Research calls it the suffocation of marriage:[12]

Americans increasingly expect marriage to fulfill higher-level needs (esteem, self-actualization)—needs that previous generations met through community, religion, or extended family. But couples are investing less time in their relationships.

The result: high expectations with insufficient investment.

Successful marriages meeting these needs report unprecedented happiness. But most couples fail to invest enough to meet the expectations they’ve set.

The implication for growth: if you expect your partner to support your self-actualization, you need to invest proportionally more in the relationship than previous generations did.

Relationship Satisfaction Trajectories

A meta-analysis of longitudinal studies found relationship satisfaction follows predictable patterns:[13]

  • Declines from age 20-40, reaching a low point around 40
  • Increases from 40-65, then plateaus
  • By relationship duration: declines first 10 years, lowest at 10 years, increases until 20 years, then may decline again

But individual differences are substantial. A 10-year study identified distinct trajectory groups:[14]

  • High stable satisfaction: Most favorable outcomes—greater positive affect, better mental health
  • Declining satisfaction: Poorer outcomes even if initially high
  • Low but stable: Better outcomes than declining group

The takeaway: initial compatibility matters less than trajectory. A couple starting at 80% satisfaction but declining will be worse off than one starting at 70% but stable.

Personality Change in Couples

Do couples influence each other’s personality over time?

A four-year study of 169 newlywed couples found:[15]

  • Partners who became more agreeable reported greater marital satisfaction
  • Partners who became less neurotic reported greater marital satisfaction
  • Personality changes predicted changes in satisfaction

Couples don’t just grow as individuals—they shape each other’s growth.

What Predicts Growing Together vs. Apart

Machine learning analysis of 43 datasets (11,196 couples) identified the strongest predictors of relationship quality:[16]

Top relationship-specific predictors:

  1. Perceived partner commitment
  2. Appreciation
  3. Sexual satisfaction
  4. Perceived partner satisfaction
  5. Conflict quality

Top individual predictors:

  1. Life satisfaction
  2. Negative affect
  3. Depression
  4. Attachment avoidance/anxiety

Relationship variables explained 45% of variance. Individual characteristics mattered, but less than how partners related to each other.

Practical Assessment

When evaluating growth trajectory compatibility, consider:

Direction:

  • Where do you each want to be in 5, 10, 20 years?
  • Are those visions compatible?
  • Have you explicitly discussed them?

Support:

  • Do you actively support each other’s goals?
  • Do you celebrate each other’s wins enthusiastically?
  • Can you support growth that doesn’t directly benefit you?

Beliefs:

  • Do you both view the relationship as something to cultivate?
  • How do you respond when challenges arise?
  • Do you see difficulties as information or as fixable problems?

Investment:

  • Are you investing enough time and energy to support the growth you expect?
  • Is the investment reciprocal?

Warning Signs

Growth trajectories are diverging when:

  • One partner’s growth is consistently deprioritized
  • Success is met with resentment rather than celebration
  • Goals are never discussed, only assumed
  • One person’s identity is subsumed entirely into the relationship
  • You can’t articulate what your partner is working toward
  • Supporting growth feels like sacrifice rather than investment

The Bottom Line

Compatibility isn’t static. The person you choose today will be different in five years—and so will you.

Research shows what helps couples grow together:

  • Self-expansion: Using the relationship as a vehicle for mutual growth
  • Growth mindset: Believing the relationship can be cultivated through effort
  • Responsive support: Facilitating partner’s goals without controlling direction
  • Goal coordination: Explicitly aligning on shared and individual goals
  • Capitalization: Celebrating successes enthusiastically
  • Sufficient investment: Matching time/energy to expectations

The couples who grow together aren’t the ones who stay the same. They’re the ones who evolve in compatible directions—because they support, celebrate, and intentionally coordinate that evolution.

Choose someone whose growth you want to support. And make sure they want to support yours.

References

  1. Aron, A., Aron, E. N., Tudor, M., & Nelson, G. (1991). Close relationships as including other in the self. Journal of Personality and Social Psychology, 60(2), 241-253. APA

  2. Aron, A., Paris, M., & Aron, E. N. (1995). Falling in love: Prospective studies of self-concept change. Journal of Personality and Social Psychology, 69(6), 1102-1112. APA

  3. Montoya, R. M., Horton, R. S., & Kirchner, J. (2008). Is actual similarity necessary for attraction? A meta-analysis of actual and perceived similarity. Journal of Social and Personal Relationships, 25(6), 889-922. Sage

  4. Knee, C. R. (1998). Implicit theories of relationships: Assessment and prediction of romantic relationship initiation, coping, and longevity. Journal of Personality and Social Psychology, 74(2), 360-370. APA

  5. Gander, F., Uhlich, M., Traut, A. C., Saameli, M. A., Bühler, J. L., Weidmann, R., & Grob, A. (2025). The role of relationship beliefs in predicting levels and changes of relationship satisfaction. Journal of Social and Personal Relationships, 42(1), 145-167. Sage

  6. Overall, N. C., Fletcher, G. J. O., & Simpson, J. A. (2010). Helping each other grow: Romantic partner support, self-improvement, and relationship quality. Personality and Social Psychology Bulletin, 36(11), 1496-1513. PubMed

  7. Feeney, B. C. (2004). A secure base: Responsive support of goal strivings and exploration in adult intimate relationships. Journal of Personality and Social Psychology, 87(5), 631-648. PubMed

  8. Ungar, N., Michalowski, V. I., Baehring, S., et al. (2021). Joint goals in older couples: Associations with goal progress, allostatic load, and relationship satisfaction. Frontiers in Psychology, 12, 623037. PubMed

  9. Rosta-Filep, O., Lakatos, C., Thege, B. K., Sallay, V., & Martos, T. (2023). Flourishing together: The longitudinal effect of goal coordination on goal progress and life satisfaction in romantic relationships. International Journal of Applied Positive Psychology, 8(Suppl 2), 205-225. Springer

  10. Gable, S. L., Reis, H. T., Impett, E. A., & Asher, E. R. (2004). What do you do when things go right? The intrapersonal and interpersonal benefits of sharing positive events. Journal of Personality and Social Psychology, 87(2), 228-245. PubMed

  11. Gable, S. L., Gonzaga, G. C., & Strachman, A. (2006). Will you be there for me when things go right? Supportive responses to positive event disclosures. Journal of Personality and Social Psychology, 91(5), 904-917. PubMed

  12. Finkel, E. J., Hui, C. M., Carswell, K. L., & Larson, G. M. (2014). The suffocation of marriage: Climbing Mount Maslow without enough oxygen. Psychological Inquiry, 25(1), 1-41. Taylor & Francis

  13. Weidmann, R., Schönbrodt, F. D., Ledermann, T., & Grob, A. (2022). Development of relationship satisfaction across the life span: A systematic review and meta-analysis. Psychological Bulletin, 148(3-4), 283-331. PubMed

  14. Roth, M., Landolt, S. A., Nussbeck, F. W., Weitkamp, K., & Bodenmann, G. (2024). Positive outcomes of long-term relationship satisfaction trajectories in stable romantic couples: A 10-year longitudinal study. International Journal of Applied Positive Psychology, 9, 1389-1410. Springer

  15. Lavner, J. A., Weiss, B., Miller, J. D., & Karney, B. R. (2018). Personality change among newlyweds: Patterns, predictors, and associations with marital satisfaction over time. Developmental Psychology, 54(6), 1172-1185. PubMed

  16. Joel, S., Eastwick, P. W., Allison, C. J., et al. (2020). Machine learning uncovers the most robust self-report predictors of relationship quality across 43 longitudinal couples studies. Proceedings of the National Academy of Sciences, 117(32), 19061-19071. PubMed