Reflections on Past Behavior: A Self‐Report Index of Habit Strength1

We argue that habit is a psychological construct, rather than simply past behavioral frequency. In 4 studies, a 12‐item index of habit strength (the Self‐Report Habit Index, SRHI) was developed on the basis of features of habit; that is, a history of repetition, automaticity (lack of control and awareness, efficiency), and expressing identity. High internal and test‐retest reliabilities were found. The SRHI correlated strongly with past behavioral frequency and the response frequency measure of habit (Verplanken, Aarts, van Knippenberg, & van Knippenberg, 1994). The index discriminated between behaviors varying in frequency, and also between daily vs. weekly habits. The SRHI may be useful as a dependent variable, or to determine or monitor habit strength without measuring behavioral frequency.