Bonnie Anderson and Dan Bjornn attended CHI 2017 this week at Denver, Colorado to present, “What Do We Really Know about How Habituation to Warnings Occurs Over Time? A Longitudinal fMRI Study of Habituation and Polymorphic Warnings.” CHI is widely considered the premier conference in the field of human–computer interaction.
We were fortunate to share the session with some of our favorite usable security researchers. The presentation went well and the questions from the audience allowed us to talk about our future research streams.
Whereas previous studies (including our own work) examined habituation at a single point in time, this study observed habituation over five consecutive days using fMRI and eye tracking simultaneously. This allowed us to measure not only the decrease in users’ attention to warnings over the course of the workweek, but also another core characteristic of habituation: response recovery—the increase in user response after a rest period during which the stimulus is absent.
We found that people habituated rapidly to repeated warnings within a single laboratory session (both in terms of decreased neural activity and fewer eye fixations). However, we observed a recovery effect of attention from one day to the next when warnings were withheld. Unfortunately, this recovery effect wasn’t enough to offset the overall pattern of habituation across the workweek. More positively, we found that a polymorphic warning with only four variations was able to significantly sustain attention over time.
Our results also add credibility to prior point-in-time studies by showing that the pattern of habituation they reported holds across a workweek, indicating that cross-sectional habituation studies can be useful proxies for habituation overtime. Additionally, the eye-tracking and fMRI results very similar, suggesting that eye tracking is a valid and cost-effective alternative to fMRI for studying the mental process of habituation.
From the abstract:
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.