A first-draft design contract for standing up an in-house drift-diffusion pipeline — testing whether perceptual decisions about random-dot motion and about graded-masked RaFD faces are governed by comparable drift-diffusion signatures, within the same people.
Listen first, then use the pages below as reference. The general deep-dive covers the
whole design contract — the two-arm structure, the three candidate versions, the golden-standard
literature comparison, the power analysis, and the open questions. The design-decisions dive
focuses on why each option was taken and on the four DDM parameters (v, a, t₀, z).
General deep-dive
Design decisions & DDM parameters
This is a contract for discussion, not a locked protocol. It lays out the full decision space — four claim tiers × three design versions — so the team can choose in the room. Every design choice below is tagged with its precedent count from a 19-paper face-DDM corpus, or explicitly flagged novel where the literature has no precedent at all.
Goal of Part 1: stand up and validate an in-house DDM data pipeline by measuring, within the same participant, whether perceptual decisions about random-dot motion and about masked RaFD faces are governed by comparable drift-diffusion signatures.
Reproduction vs. novel — stated plainly. The face arm is not a strict
reproduction. Across the 19 face-2AFC-DDM papers reviewed, no study combines RaFD
faces + graded masking + strict 2AFC + a full v/a/t₀/z fit, on either the gaze or
emotion axis. What is reproducible is (a) the RDM arm (Palmer, Huk & Shadlen 2005PDF —
well established) and (b) the direction of the face effect (masking lowers drift —
Williams et al. 2023PDF). Part 1 therefore reproduces established directions and methods while being, in
combination, a novel design — which is precisely where the publishable contribution sits.
See the Gaps & open questions page.
A one-view map of how this knowledge base is organised — from the design, through the stimuli and the drift-diffusion model, to the evidence and the power decision.