2.2.2. Other measures

Validation sample participants completed additional motivation measures for comparison to our novel scale. The QLS-IM [63,77] and GCOS-CP Autonomy subscale [39] were used to assess convergent validity with trait IM, and GCOS-CP Control was used to assess discriminant validity (expected not to correlate with trait IM, but rather with EM). The Intrinsic Motivation Inventory for Schizophrenia Research (IMI-SR) [60] measured state IM in response to the completion of an in-scanner visual fractal memory fMRI task; fMRI results will be described in a future paper. We explored the relationship between the IMI-SR and trait IM without expectations regarding convergence or divergence, due to prior mixed findings regarding whether state IM correlates with trait motivation measures [44,78]. To assess our scale’s utility with respect to understanding clinical amotivation, participants completed the interviewer-rated Clinical Assessment Interview for Negative Symptoms (CAINS) [79,80] with an interviewer blind to self-report results. In the CAINS higher ratings indicate more severe symptoms; we therefore use the term “clinical amotivation” to describe our summary score of the motivation items, which are a subset of the items from the “motivation and pleasure” subscale of the CAINS. Note we evaluate CAINS relationships in relation to utility rather than validity, because the CAINS was not designed to differentiate between IM and EM. This analysis therefore addressed an important unsettled question in the field and tested the utility of our scale by characterizing these relationships. See Supplementary Methods for additional details regarding these measures.