SOMA Validation RCT: Testing Structural Equivalence and Mechanistic Orthogonality of an Open-Source Mindfulness Stimulus Library

Background: Mindfulness research faces two structural problems. First, weak active control conditions make it impossible to isolate specific mechanisms from expectancy and non-specific effects. Second, most protocols systematically exclude low-socioeconomic status (SES) populations through design assumptions that presuppose high literacy, quiet private spaces, and familiarity with contemplative practice.

Objective: This study validates the Standardized Open-source Mindfulness Architecture (SOMA), the first modular, open-source stimulus library purpose-built to address both challenges simultaneously. SOMA comprises 88 distinct audio assets organized around 16 sensory practice modules, each paired with a structurally equivalent active control script engineered to induce analytically orthogonal cognitive processing.

Design: Pre-registered randomized controlled trial using a 2×2 mixed design (Condition \[Mindfulness vs. Active Control\] × Measure \[State Mindfulness Scale vs. Analytical Engagement Scale\]), with quota sampling to ensure equal representation of participants with and without a university-level degree (n = 180 per SES stratum).

Setting: Online, via Prolific Academic recruitment platform and Qualtrics survey software.

Participants: N = 360 English-proficient adults aged 18 years and older (or the applicable minimum age of majority in the participant's country of residence) without a current mental health diagnosis or treatment, and without a current meditation practice.

Intervention: Each participant listens to a single 12-minute audio-guided exercise. Participants are randomly assigned to either the Mindfulness condition or the Active Control condition, and within that condition to one of 16 practice scripts. Mindfulness scripts guide bottom-up experiential awareness; Active Control scripts guide top-down analytical processing of the same everyday activities.

Primary Outcomes: (1) Credibility and expectancy equivalence between conditions (H1: Two One-Sided Tests on Credibility and Expectancy Questionnaire composite, equivalence bounds d = ±0.40); (2) mechanistic double dissociation - higher state mindfulness in the Mindfulness condition and higher analytical engagement in the Active Control condition (H2: 2×2 mixed ANOVA, interaction term as primary criterion).

Exploratory Outcome: SES-related differential experiential accessibility (H3: independent-samples t-test plus equivalence test on Semantic Differential composite by SES group).