Hello,

From reading of the article, the responses to the items for the intrinsic scale found in Appendix A can be added to form a total scale score (pp 187-188 explains this). Because they all load positively on the same factor, they form a single scale and there are no items that are reverse-coded (a careful reading of the items also suggests that there is no reverse-coding).

For the extrinsic scale, the authors suggest that a total extrinsic score can be calculated from 13 items to form a total score, but also three separate scores can be calculated. The subscales and their items can be seen in Appendix B. Note that the authors recommended dropping some of the items identified in Appendix B (they list the items on page 188).

You may want to look at other research that has used this measure (e.g., articles that have cited the Lepper et al study) to determine whether more recent changes to the instrument have been made.

If I misunderstood your question and you want the original Harter scale, here it is...

Harter, S. (1981). A new self-report scale of intrinsic versus extrinsic orientation in the classroom: Motivational and informational components. Developmental psychology, 17(3), 300.