wo years into the COVID-19 pandemic -- and 1 year after vaccines first became available -- there are still those who are opting out of getting vaccinated. Deep distrust in government and science are among the reasons that some are continuing to hold out on the shots. But experts suggest that there are psychological barriers that may have nothing to do with mistrust. To understand all of the factors at play, we need to first recognize how the mind processes the act of making a decision -- whether it is to opt in or out. On this week's episode, Gretchen Chapman, PhD, department head of social and decision sciences at Carnegie Mellon University in Pittsburgh, joins us to help us understand the psychology behind COVID vaccine refusal.