This study investigated how affective factors impact participation in science learning using structural equation modeling. Using a dataset from Taiwan, a model was obtained that showed the relationships among science-related interest, enjoyment, self-efficacy, self-concept, competency, leisure time engagement, and future interest in science. The paths relating to engagement and future interest were much stronger for interest and enjoyment than for self-efficacy and self-concept. There was no significant path between science competency and future science interest or engagement. The results suggest that the affective and cognitive pathways to scientific competency are divergent and that they might be differentially activated by different contexts and activities. This indicates that school science educators might wish to reconsider the merit of overemphasizing achievement in comparison to interest. Finally, the results suggest that the development of science competency per se may not be the best way to ensure public engagement and understanding of science.