Personality, time of day, and caffeine: some theoretical and conceptual problems in Revelle et al.

Revelle et al. have provided convincing evidence of interesting and replicable empirical relationships between the factors of time of day, caffeine administration, and impulsivity. Furthermore, their data suggest that differences between introverts and extraverts in time of day effects are due more to the impulsivity component of extraversion than to the sociability component. However, their preferred interpretation of the data in terms of a unidimensional arousal model is seriously deficient and should be replaced by a more complex conceptualization that emphasizes the existence of a number of qualitatively distinct activation states and that focuses on the effects of each of these activation states on the componential functions of information processing.