Filling time versus affective response to the activity that fills the time: independent effects on time judgment?

Previous time perception research has confounded manipulations intended to evoke different affective reactions to the task with different levels of nontemporal processing demands. An attempt was made to separate these dimensions by a social comparison procedure aimed at making the same concurrent task (card sorting) appear differentially interesting to two groups of college students. Response uncertainty varied within the task to that processing demands could be compared while reported interest in the task varied between groups. Magnitude of time estimates related inversely to response uncertainty, but reported interest in the task made no independent contribution to the variance of estimates.