<p>This study investigates the developmental evolution of motivational specificity within the Self-Determination Theory framework. Motivational regulations range from controlled to autonomous forms, and evidence suggests they become more differentiated with age. Yet, this developmental trajectory remains underexplored. Based on the Specificity Hypothesis, we expected autonomous motivations (intrinsic and identified) to become more specific over time, while controlled motivations would remain stable. We tested this among secondary school students (grades 9–11), assessing motivation across academic subjects. Results show that only autonomous regulations—especially intrinsic motivation—exhibited increasing specificity with age. We also observed stronger correlations between motivation and self-concept within subjects over time. These findings support the Specificity Hypothesis and suggest that the development of autonomous motivation involves growing contextual differentiation. In contrast, controlled regulations remained relatively stable. This study highlights the role of self-concept in motivational development and provides new insights into how motivational regulations evolve. Future research should examine these trajectories in broader contexts to confirm and extend these findings.</p>