Abstract. How do we know when an activity has exhausted us or helped us recover? In this paper, we present a motivational approach to exhaustion and recovery that takes into account the multidimensional nature of the constructs. The account details three psychological processes that may – individually and in interaction – underlie exhaustion and recovery. Specifically, we propose that changes in mood, subjective time perception, and opportunity costs experienced during an ongoing effortful or relaxing activity indicate a person’s momentary degree of exhaustion and recovery and impact the decision of whether the person should continue or disengage from the activity at hand. Addressing developmental changes across adulthood, we present two opposing hypotheses on how younger and older adults may differ in their experiences of exhaustion and recovery: (i) Older adults may experience an accelerated subjective time perception compared to younger adults and may thus feel less exhausted (more recovered) than younger adults after spending an identical amount of time engaged in an effortful (relaxing) activity. (ii) Older adults may be more sensitive toward increasing opportunity costs experienced during an effortful or relaxing activity and may therefore feel exhausted or recovered faster than younger adults.

Two studies investigated subjective conceptualizations of energy for goal pursuit across adulthood. Study 1 (N ϭ 276, 20 -92 years of age) explored age-related differences in the (a) endorsement of a limited versus nonlimited account of energy for goal pursuit, (b) amount of energy available for physically, mentally, socially, and emotionally demanding activities, and (c) extent to which spending energy on a demanding activity inhibits or facilitates energy expenditure for subsequent activities, both within and across functional domains. Study 2 (N ϭ 147, 18 -86 years of age) experimentally induced energy loss through a 20-min physical exercise and examined age-related differences in the increase of subjective exhaustion and opportunity costs as a motivational cue for goal disengagement. With increasing age, adults more strongly endorsed a nonlimited account of energy and perceived having more energy available for personally relevant social activities. However, older adults also reported higher negative cross-domain energy spillover after physical exertion. Multilevel growth curve models further revealed that, compared with younger adults, older adults reported a steeper initial increase in exhaustion and opportunity costs during physical exercise, but converged with the younger age groups again at the close of the exercise session. The discussion centers around the importance of selectivity in older adulthood and motivational accounts of effort and exhaustion.

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Future automotive interior lighting might have the potential to go beyond decorative purposes by influencing alertness, circadian physiology, and sleep. As the available space in the interior of an automobile for lighting applications is limited, understanding the impact of various luminous surface sizes on non-image-forming effects is fundamental in this field. In a laboratory study using a within-subject design, 18 participants were exposed to two bright light conditions with different solid angles and one dim light condition in a balanced, randomized order during the course of the evening. Our results demonstrate that both light conditions significantly increased subjective alertness and reduced salivary melatonin concentration but not cognitive performance compared to dim light. The solid angle of light exposure at constant corneal illuminance only affected visual comfort. While subjective alertness can be increased and melatonin can be attenuated with rather small luminaires, larger solid angles should be considered if visual comfort is a priority.