A temporary deficiency in self-control: Can heightened motivation overcome this effect?

Changes in Subjective Motivation and Effort During Sleep Restriction Moderate Interindividual Differences in Attentional Performance in Healthy Young Men

PURPOSE

The effects of sleep restriction on subjective alertness, motivation, and effort vary among individuals and may explain interindividual differences in attention during sleep restriction. We investigated whether individuals with a greater decrease in subjective alertness or motivation, or a greater increase in subjective effort (versus other participants), demonstrated poorer attention when sleep restricted.

PARTICIPANTS AND METHODS

Fifteen healthy men (M±SD, 22.3±2.8 years) completed a study with three nights of 10-hour time in bed (baseline), five nights of 5-hour time in bed (sleep restriction), and two nights of 10-hour time in bed (recovery). Participants completed a 10-minute psychomotor vigilance task (PVT) of sustained attention and rated alertness, motivation, and effort every two hours during wake (range: 3-9 administrations on a given day). Analyses examined performance across the study (first two days excluded) moderated by per-participant change in subjective alertness, motivation, or effort from baseline to sleep restriction. For significant interactions, we investigated the effect of study day² (day*day) on the outcome at low (mean-1 SD) and high (mean+1 SD) levels of the moderator (N = 15, all analyses).

RESULTS

False starts increased across sleep restriction in participants who reported lower (mean-1 SD) but not preserved (mean+1 SD) motivation during sleep restriction. Lapses increased across sleep restriction regardless of change in subjective motivation, with a more pronounced increase in participants who reported lower versus preserved motivation. Lapses increased across sleep restriction in participants who reported higher (mean+1 SD) but not preserved (mean-1 SD) effort during sleep restriction. Change in subjective alertness did not moderate the effects of sleep restriction on attention.

CONCLUSION

Vigilance declines during sleep restriction regardless of change in subjective alertness or motivation, but individuals with reduced motivation exhibit poorer inhibition. Individuals with preserved subjective alertness still perform poorly during sleep restriction, while those reporting additional effort demonstrate impaired vigilance.

Outsiders’ Thoughts on Generating Self-Regulatory-Depletion (Fatigue) Effects in Limited-Resource Experiments

We offer thoughts pertaining to purported conceptual and replication crises that have been discussed in relation to the limited-resource model (LRM) of self-control, functioning as crisis outsiders who have been conducting related research concerned with determinants and cardiovascular correlates of effort. Guiding analyses in our laboratory convey important lessons about experimental generation of the now-classic LRM self-regulatory-fatigue effect on control. They do so by drawing attention to conditions that must be met in fatigue-induction and fatigue-influence phases of relevant experiments. One fundamental lesson is that even highly standardized fatigue-induction protocols cannot be expected to consistently allow definitive tests of this effect. Another is that the effect might emerge consistently only in a behavioral-restraint “sweet spot” of sorts—a multidimensional motivational space wherein rested study participants view restraint as possible and worthwhile and fatigued participants do not. Implications are identified and discussed.