Name: Kai Xue

School of Psychological and Brain Sciences – Ph.D. Dissertation Defense Meeting

Date: Tue, Nov 10th, 2026

Time: 10:00 AM - 11:00 AM EST

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

Dissertation Committee Chair/Advisor:

Dobromir Rahnev, Ph.D. (Georgia Tech)

Dissertation Committee Members:

Tansu Celikel, Ph.D. (Georgia Tech)

Sashank Varma, Ph.D. (Georgia Tech)

Mengyao Li, Ph.D. (Georgia Tech)

Megan Peters, Ph.D. (University College London)

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.