Name: Kai Xue

Ph.D. Dissertation Proposal Meeting

Day/Time: Thursday, February 26th, 2026 – 12:30 PM Eastern Time

Location: https://gatech.zoom.us/my/kaixue

Advisor: Dobromir Rahnev (Georgia Tech)

Dissertation Committee Members:

Dr. Sashank Varma (Georgia Tech)

Dr. Tansu Celikel (Georgia Tech)

Dr. Mengyao Li  (Georgia Tech)

Dr. Megan Peters (University of California, Irvine)

Title: The Computation of Confidence in Perceptual Decision-Making 

Abstract: This dissertation investigates the computational mechanisms underlying confidence in perceptual decision-making through three related studies. Study 1 uses transcranial magnetic stimulation (TMS) to establish when confidence is computed, revealing that the dorsolateral prefrontal cortex (DLPFC) contributes to confidence during a broad temporal window overlapping with decision-making. Study 2 tests competing computational theories — Bayesian Confidence Hypothesis (BCH) versus Confidence in Raw Evidence Space (CRES) — in two-choice tasks, finding consistent support for evidence-based rather than probability-based confidence computation. Study 3 extends this investigation to multi-alternative decisions using a novel dot numerosity paradigm, demonstrating that confidence tracks the difference between the two highest evidence values rather than choice probability. Together, these studies advance a mechanistic framework in which confidence emerges in parallel with decisions and operates on sensory evidence rather than probability estimates.