Clocking self-regulation: why time of day matters for health psychology.

Various lines of research have identified a number of factors that can impair a person's ability and motivation to exercise self-control, here self-regulation, in the face of a tempting object (e.g., food, sex, alcohol/drugs, smoking). Each of these in situ factors - the availability of the tempting object, one's desire for it, and impaired affective and cognitive functioning (most notably from sleep-related fatigue, daily 'wear and tear', and intoxication) - makes self-regulation more difficult, and even more so when they co-occur. This integrative paper highlights how time of day modulates the salience of these impairing factors and argues that they are likely to be especially influential on self-regulation at night, or later in one's waking day. As each factor is likely to vary considerably across the 24 hours of a day, so too will one's self-regulatory ability and motivation - although person-level characteristics such as chronotype may shift these time-based considerations. The paper thus emphasises the importance of clocking self-regulation within health psychology research and intervention design. Consideration of when a self-regulation attempt is being made and of how time of day (or night) may be altering both the person and the situation towards risk, will facilitate a more temporally contextualised account of self-regulation.