Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 2007.Includes bibliographical references (leaves 114-123).To what extent can experience shape perception? In what ways does perception vary across people or even within the same person at different times? This thesis presents three lines of research examining the role of experience on perception. The first section presents evidence from synesthesia suggesting that learning can influence letter-synesthesia pairings and that associative learning can affect relatively early visual processing. The second section examines the role of linguistic categorization in color judgments, finding that language can play an online role even in a relatively simple color discrimination task. The final section examines how perception adjusts over relatively short time scales using face adaptation. The adaptation experiments show that adaptation to faces can improve recognition performance on famous faces. The results further demonstrate that these effects can be obtained without extensive training and that contrary to proposals from experiments using face spaces, that identity based adaptation effects can be found on trajectories which do not pass through the average face.by Nathan Witthoft.Ph.D.