4. Evolutionary Trait: Evolution Dimension
Arthur Aron's Self-Expansion Theory (1986)
Theoretical Background
Theoretical Origins & Development: The Evolution dimension is grounded in the Self-Expansion Theory proposed by Professor Arthur Aron at SUNY Stony Brook in 1986. Aron integrated self-concept research from social psychology with intimate relationship literature, proposing a core thesis: humans possess an intrinsic motivation to expand self-cognition, capabilities, and resources through intimate relationships. This theory has been published in top journals including the Journal of Personality and Social Psychology and supported by multiple experimental studies.
Core Mechanism: Self-Expansion Theory posits that when individuals enter intimate relationships, they incorporate partners' resources, perspectives, and identity into their self-concept (termed "Including Other in Self," IOS). This self-expansion experience generates excitement and satisfaction, serving as an important source of early relationship passion. Aron's research found that when self-expansion rate slows (as relationships enter stable phases), relationship satisfaction often declines—unless partners continue creating new shared experiences.
RSTI's Simplification Logic: Based on Self-Expansion Theory, RSTI categorizes individual expectations for relationship development into two orientations: Static types value the secure foundation and predictability of relationships, deriving satisfaction from stability; Growth types value continuous development and novel experiences, deriving satisfaction from expansion. These orientations reflect fundamental assumptions about the "ideal relationship trajectory."
Static (S)
Static / Maintenance-Oriented
Static individuals view relationships as a secure base, valuing deepening existing connections over constant change. Characteristics include: preferring predictable daily interaction patterns, cherishing established rapport and traditions, and approaching change cautiously while tending to maintain relationship stability. Static types derive security from relationship consistency and reliability, believing depth comes from accumulated time rather than stacked novel experiences. Within the attachment theory framework, static tendencies partially overlap with secure attachment. Research shows static orientation is more common in later relationship stages, parenting phases, and high-stress periods.
Growth (G)
Growth / Exploration-Oriented
Growth individuals view relationships as a platform for joint development, valuing continuous self-expansion through partners. Characteristics include: pursuing novel experiences and shared challenges, expecting relationships to bring personal growth and expanded horizons, feeling uneasy with stagnation, and tending to drive dynamic relationship development. Growth types derive satisfaction from relationship expansiveness and stimulation, viewing growth as an indicator of relationship vitality. Aron's experimental research shows that couples participating in novel exciting activities together report significantly higher relationship satisfaction than control groups doing only routine activities, with this effect particularly pronounced in growth-oriented individuals.
Key Insights
- 1
Aron's Classic Experiment: In controlled experiments, couples randomly assigned to novel challenging activities (such as three-legged races) reported significantly higher relationship quality and attraction compared to control groups doing ordinary activities (such as ball sports). This supports the core predictions of Self-Expansion Theory.
- 2
Common Tension Patterns: When growth types feel relationship stagnation, they may exhibit change-driving behaviors (proposing new plans, challenging status quo); static types may interpret this as dissatisfaction with the current state or rejection of themselves. Conversely, static types' tendency to maintain status quo may be interpreted by growth types as lacking initiative or unwillingness to invest. Understanding this as orientation difference rather than relationship problems is key to resolving tension.
- 3
Complementarity & Balance: Research indicates that static-growth pairings are not inevitably conflictual. Static types provide relationship security foundation while growth types provide developmental momentum—if both can understand each other and alternate leadership, they can form complementary dynamic balance. The key is avoiding interpreting the other's orientation as a flaw or threat.