Components of events and processes.

Rips and Estin (1998) provided evidence that mental events such as dreaming are more homogeneous than physical events such as checking out a book; that is, their parts are more difficult to distinguish. In their experiment, participants listed more distinctive properties for the parts of physical events than for the parts of mental events. However, the physicality of stimuli was confounded with temporal aspects. Mental stimuli tended to be processes, and physical stimuli, events. This study tested homogeneity with new stimuli separating out the factors of physicality and aspect. Consistently, both physicality and aspect had significant effects on the perceived homogeneity of activities, as measured by the number of listed parts, the number of distinctive properties of each part, and homogeneity ratings. The study shows that homogeneity is strongly influenced by aspect but that physicality remains a robust factor for homogeneity, even after taking aspect into account.