Fig. 2: Four approaches to designing experimental challenge skill balance conditions.
From: A framework for neurophysiological experiments on flow states

This figure shows how different experimental designs match task challenges with the skills of two hypothetical participants. The perfect challenge skill balance is lower for participant 1 (orange) than for participant 2 (blue), leading to variable adjustments in challenge levels between the four examples. a. Challenge levels in all conditions are fixed and not tailored to participants’ skills. For participant 2, the flow condition is below their challenge skill balance, and for participant 1, the flow condition is above it. b. Challenge levels in easy and hard conditions are fixed but the flow condition is personalised to each participants’ skills (e.g., by setting participants’ task challenge level using their pre-experimental performance). Whilst flow is likely for both participants (since the flow condition is personalised), participant 2 may experience flow in the hard condition because the hard challenge level is nearly balanced with their skills (as indicated by the blue dashed line position). c. Challenge levels in all conditions are personalised to participant skills (e.g., using pre-experiment performance data). First, the flow condition challenge level is set, then, challenge levels in the easy and hard conditions are set based on a standardised decrease or increase (respectively) from the challenge level of the flow condition. This ensures the difference in challenge levels between all three conditions is consistent for every participant, unlike in a and b. d. Challenge levels in all conditions are continuously tailored to participant skills using real-time performance data. Challenge level in the flow condition is dynamically adjusted to real-time performance results and challenge levels in the easy and hard conditions are also dynamically adjusted at a standardised decrease or increase (respectively) from the flow condition difficulty. Like in c, this ensures the difference in challenge levels between all three conditions is consistent for every participant, unlike in a and b.