What Do We Really Know about How Habituation to Warnings Occurs Over Time?: A Longitudinal fMRI Study of Habituation and Polymorphic Warnings

A major inhibitor of the effectiveness of security warnings is habituation: decreased response to a repeated warning. Although habituation develops over time, previous studies have examined habituation and possible solutions to its effects only within a single experimental session, providing an incomplete view of the problem. To address this gap, we conducted a longitudinal experiment that examines how habituation develops over the course of a five-day workweek and how polymorphic warnings decrease habituation. We measured habituation using two complementary methods simultaneously: functional magnetic resonance imaging (fMRI) and eye tracking. Our results show a dramatic drop in attention throughout the workweek despite partial recovery between workdays. We also found that the polymorphic warning design was substantially more resistant to habituation compared to conventional warnings, and it sustained this advantage throughout the five-day experiment. Our findings add credibility to prior studies by showing that the pattern of habituation holds across a workweek, and indicate that cross-sectional habituation studies are valid proxies for longitudinal studies. Our findings also show that eye tracking is a valid measure of the mental process of habituation to warnings.