Fatigue States are Multidimensional: Evidence from Studies of Simulated Driving

A recent NIOSH report on driver fatigue (Hitchcock & Matthews, 2005) discussed evidence that subjective fatigue states are multidimensional; comprised of several components. Vehicle driving may provoke different patterns of response on these components, depending on the source of fatigue, with differing implications for safety. However, existing fatigue inventories do not adequately survey these different components of fatigue state. For example, changes in the driver’s cognitions of personal competence are poorly sampled by existing measures. This paper will review key findings from two recent experimental studies of fatigue (Ns = 108, 180) that used a STISIM Model 400 simulator. Building on earlier work (e.g., Matthews & Desmond, 2002), simulator drives were designed so as to induce fatigue. The first aim of these studies was to differentiate qualitatively different patterns of subjective response corresponding to ‘active ’ fatigue (derived from prolonged high workload) and ‘passive’ fatigue (derived from chronic understimulation). The second aim of these studies was to explore the psychometric properties of a new multidimensional fatigue inventory developed for NIOSH. Results will be presented that support the multidimensional fatigue model, and that demonstrate the different patterns of subjective response that may be labeled as “fatigue”. Methodological implications for investigating fatigue using simulator methods will be discussed