Flow measurement is contested — 2025 systematic review (Wonders, Human Behavior and Emerging Technologies) found most studies fail to screen flow-proneness or match difficulty to skill, undermining confidence

Claim: No single instrument cleanly identifies in/out of flow; operationalisation is criticised as imprecise (Løvoll & Vittersø 2014; review in Frontiers/PMC 2020 "Investigating the 'Flow' Experience"). A 2025 systematic review (Wonders, Human Behavior and Emerging Technologies) found most studies fail to screen for flow-proneness or match task difficulty to skill, undermining confidence.

Source: Wonders 2025 systematic review (Human Behavior and Emerging Technologies); Løvoll & Vittersø 2014; PMC 2020 review.

Confidence: Verified (limit / methodological).

Why this matters for Candid: Reason to claim "supports absorption / engagement" for tools — not "induces deep flow." Anchors R2 — Engineer the robust flow components (clear-goal + immediate-feedback); do NOT promise "deep flow" for short tool sessions; the challenge-skill balance is shaky and contested. Mirrors the discipline of R7 — Do NOT invoke the Zeigarnik memory claim in client conversations or content; use goal-gradient / Ovsiankina instead — the memory effect failed to replicate in 2025 meta-analysis from Brief E.